Efficacy of filter top cages to reduce cross-contamination in mice housed in experimental facilities

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However, contamination is difficult to avoid during long experimental procedures when animals spend time outside their enclosures, in contact with users and different equipment. To evaluate the efficacy of filter-top cages to minimize cross contamination when experimental mice of different microbiological status share the same room, we studied a complete panel of microorganisms in mice housed in different systems. C57BL6/N mice were purchased to an SPF facility: one group was housed in filter top cages whereas another group stayed in similar cages but without the filter-top. These external mice shared the room with mice involved in other experimental protocols between 8 and 13 weeks. A group of conventional mice born at our facilities housed in open cages served as control. Samples from different organs were analyzed by PCR. Mice born at the experimental facility were positive for several bacteria, virus, and parasites. All the bacteria present in this control group, were also found in the group of mice originally SPF housed in the open cages. Only 2 out of the 6 viruses present in the facilities were transmitted to the external mice in open cages, whereas no parasites were detected. Interestingly, mice housed in the filter-top system only recovered 3 bacteria from all the microorganism present in the facilities. Our results shown that using filter-top cages for long periods may be a refinement tool when there is no alternative to share the room with mice of different microbiological status. Introduction From the first wooden and glass cages used to house laboratory mice to the modern individual ventilated cages (IVC), the design of mice microenvironment has evolved to promote animals’ physical comfort as well as to enable effective sanitary maintenance ( 1 ). A milestone in laboratory animal science took place in 1958, when transmission of epidemic diarrhea of infant mice was controlled by housing mice in cages fashioned of galvanized wire mesh covered with fiberglass insulation serving as a passive air filter ( 2 ). This principle was improved in several ways until the first transparent plastic shoebox with filter paper inserts on the top, commercially available in 1982 ( 3 ). Although this type of cage allows to keep filtered air inside the cage, some reports warned against increases of ammonia levels in cage environments ( 4 – 6 ). Therefore, these microisolation cages were then placed on mass air displacement racks, improving the microenvironment parameters. The ultimate step in housing conditions was provided by the positive, individually ventilated microisolation caging system, in which the air is actively filtered before going into the cages. Most modern breeding facilities employs IVC to house mice colonies, but this is not always warranted in experimental facilities. Since the landing of these modern types of housing systems, several studies evaluated their efficacy to prevent contamination of particular virus and bacteria, with results varying depending on the type of agent. Proliferation of Mycoplasma pulmonis in the lungs of mice experimentally infected was not significantly different between filter-top cages and IVC ( 7 ). Another study showed no alteration in morbidity caused by Corynebacterium bovis in immunodeficient mice housed either in filter-top or wire-top cages ( 8 ). On the contrary, a partial effect of filter-top cages in preventing transmission of Mouse Hepatitis Virus (MHV) among mice was demonstrated ( 9 ). Likewise, transmission of MHV after 8 weeks of exposition to open cages with infected animals, was verified in mice housed in open cages, whereas only mice in 2 out of 10 filter-top cages seroconverted, and no mouse housed in IVC was positive ( 10 ). To analyze these different reports, it is important to consider that, beside the housing system, husbandry techniques may substantially differ among facilities, influencing the final results. Remarkably, no report has been published up to now, comparing the microbiological status of animals housed in different enclosures. The health status of experimental animals is critical, not only for welfare concerns, but also, because microorganisms present in laboratory animals, even at a subclinical level, can widely affect experimental results ( 11 ). Several reports point to specific alterations in the neurobehavioural phenotype of laboratory mice depending on the housing system. Indeed, it is not surprising that the microenvironment can modify experimental results given its direct influence on the behavior of enclosed animals. C57BL/6JArc mice of either sex, raised in IVC systems showed more anxious-like behaviors in the elevated plus maze, and were socially more active than mice housed in the classic filter-top cages ( 12 ). The same laboratory demonstrated that schizophrenia-relevant endophenotypes previously validated in transgenic mice housed in filter-top cages were altered when mice were allocated in IVC housing ( 13 ). Another study in a transgenic mouse model for amyotrophic lateral sclerosis found that although central behavioural deficits were evident in both types of housing, responses were (moderately) impacted by IVC housing compared with filter-top cages ( 14 ). Therefore, although IVC housing improved the control of microorganism transmission, alterations on behavioral traits were also described. The use of mice of known microbiological status is key to ensuring reproducibility of experimental results. Nevertheless, it is not always possible to keep the microbiological status of animals along the experimental procedures, even more when procedures last weeks or months. Contamination of experimental animals can be minimized by employing biosecurity measures, following standardized operative procedures, and maintaining equipment sanitation, and personal hygiene routines. Our laboratory is devoted to the field of neuroscience, conducting behavioral, neurochemical, and histological assays in the experimental facilities of our Institute. Given that this experimental facility receives mice from different vendors or laboratories, and that animals are housed in open cages, it is difficult to keep mice free of infectious agents. We define, therefore, a refinement strategy that could lead to minimize the possibility of cross contamination, by employing filter-top cages. SPF-certified mice were brought to our institutional facility and a health monitoring was conducted 2–3 months later, proving that the strategy was effective in limiting contamination, specifically for viruses and parasites. Materials and Methods Animals Twenty-seven mice were used for the whole study. All of the animals were involved in unrelated, non-invasive studies, mainly as breeders. Fifteen male and female C57BL6/N elite mice were purchased at the Instituto de Medicina Experimental, (IMEX) Academia Nacional de Medicina, Buenos Aires, Argentina. The remaining 12 mice, were male and female C57BL6/N mice born at the facilities of the Instituto de Biología Celular y Neurociencia (IBCN), Facultad de Medicina, Universidad de Buenos Aires. Experiments on animals were conducted according to local regulations and were approved by the Institutional Ethical Committee (UBA Resol. 1848/2023 FMED). Seven week-old mice, bred in barrier-conditions to maintain an SPF status (as certified by Charles River), were transported in environmental controlled conditions from the IMEX to our institute animal facilities. When arrived, a group of mice (n = 6) were immediately housed in 1284L Eurostandard Type II Long (365 x 207 x 140 mm) Tecniplast microisolator cages with filter tops covered with polyester filter sheets (atmospheric dust efficiency of 92% on 8–10 um particles) whereas another group (n = 9) were housed in the same cage model but without the filter-top (two to three mice per cage). Mice stayed isolated for a week in the quarantine room before moving to the stock room, where they shared racks with mice involved in other experimental protocols. Animals were maintained under controlled conditions, i.e., 22 ± 2°C room temperature, 60% relative humidity, 12–12 h light–dark cycle (lights on at 7.00 am). Mice received ad libitum pelleted food for rodents (Cooperación) and tap water. White pine shavings were used as bedding and 8–10 g of tissue paper was added as nesting material in all the cages. Some of these mice were used as breeders, and their litter employ in other projects. The 12 mice born at the IBCN facilities were used in different experiments or as breeders and were housed in polycarbonate open cages (300 x 200 x 140 mm). External animals were provided with a health monitoring recently obtained from Charles River corresponding to the molecular diagnostic by polymerase chain reaction (PCR) assays covering several pathogen-specific genomic sequences, all of which were negative. The IBCN facilities regularly receives animals from different vendors or research facilities, and no routine health monitoring is done. However, arriving animals must bring their corresponding health monitoring report and they remain in the quarantine room for one week under observation of technical staff. These facilities do not breed mice, except from certain transgenic lines. Routine procedures Mice housed in the microisolators (with or without filter-tops) were exclusively manipulated by the researchers in charge, and the technical staff of the facility was never in contact with these animals. Cages were changed twice weekly, manipulating filter-top cages first and then, the open ones. Additionally, cages were opened once a day every day when female breeders were pregnant or give birth. Microisolators were not changed inside a changing station, but on a bench. Personnel manipulating mice wore lab coats, gloves, face masks, and head covers as personal protective elements. Bedding and nesting material were autoclaved at 134ºC for 10 minutes. Cages and bottles were manually washed with detergent and disinfected with bleach or ammonium (alternating every month). Filter sheets were washed with detergent and disinfected with bleach only once, at the beginning of the experiment. Food and tap water did not receive any decontainment treatment. Experimental Procedures Experimental groups were defined as follows: Group 1: external SPF mice housed in filter-top cages; Group 2: external SPF mice housed in open cages; Group 3: conventional mice born at our facilities housed in open cages (Table 1 ). External SPF mice stayed in our facility between 8 and 13 weeks, whereas mice born at our own facility were between 8 week- and 1 year-old (Table 1 ) at the moment we used them. At the end of the experiment, animals were killed by cervical dislocation and samples were immediately collected from the lungs, salivary glands, liver, spleen, and cecum. Fresh stool was also recovered from the rectum. Samples were kept at -60°C until shipping for microbiological analysis. Samples from mice of the same experimental group obtained at different time points were pooled for the microbiological analysis in 3 different tubes: ( 1 ) feces, ( 2 ) cecum, and ( 3 ) the 4 other organs as requested by the Laboratorio de Animales de Experimentación (LAE), Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, the national reference center where the health monitoring was conducted. Following international recommendations ( 11 ) and international ( 15 ) and local prevalence of microorganisms, several bacteria, viruses, and parasites, as shown in Tables 2 to 4 , were evaluated by PCR testing, a technique known by its high specificity and sensitivity. The microbial status of external mice was not confirmed upon receipt. Table 1 Origin animal facility, sex, age, and housing conditions of experimental C57BL6/N mouse groups Experimental group Origin Time at IBCN Cage type Sex (M: F) Age 1 IMEX 8 weeks Filter-top 3:0 15 weeks 1 IMEX 10 weeks Filter-top 0:3 17 weeks 2 IMEX 8 weeks Open 3:2 15 weeks 2 IMEX 13 weeks Open 0:4 20 weeks 3 IBCN 8–12 weeks Open 1:5 8–12 weeks 3 IBCN 1 year Open 3:3 1 year Table 2 PCR assessment of bacterial presence in samples from experimental C57BL6/N mouse groups with two animal facility origins under distinct housing conditions Bacteria PCR Group 1 Filter-top IMEX Group 2 Open IMEX Group 3 Open IBCN Bordetella bronchiseptica + + + Bordetella pseudohinzzi - - - Filobacterium rodentium (CAR bacillus) + + + Citrobacter rodentium - - - Campilobacter spp. - - - Clostridium piliforme (Tyzzer) - - - Francisella tularensis - - - Corynebacterium bovis + + + Corynebacterium kutscheri - - + Helicobacter spp (H. hepaticus; H. bilis; H. rappini) - + + Klebsiella oxytoca - - - Klebsiella pneumoniae - - - Rodentibacter spp. (R. heylii; R. pneumotropicus; R. ratti) (ex-Pasteurella pneumotropica) - - - Mycoplasma pulmonis. - - - Leptospira spp. - - - Listeria monocytogenes - - - Proteus mirabilis - - - Pseudomonas aeruginosa - - - Pneumocysitis spp. (P, carinii; P. mutina) - - + Salmonella spp. - - - Shigella spp. - - - Staphilococcus aureus - - - Streptococcus pneumoniae - - + Streptococcus Beta hemolítico - - - Streptobacillus moniliformis - - - Table 3 PCR assessment of viral presence in samples from experimental C57BL6/N mouse groups with two animal facility origins under distinct housing conditions Virus PCR Group 1 Filter-top IMEX Group 2 Open IMEX Group 3 Open IBCN Adenovius (MAd-1; MAd-2) - - - Virus de la Pneumonía (PVM) - - + Astrovirus del ratón (AstV tipo 1–2) - + + Virus Sendai (SeV) - - - Norovirus murino (MNV 1–4) - + + Virus diminuto del ratón (MVM) - - - Virus Elevador de la Lactatodeshidrogenasa (LDH) - - - Virus de la linfocoriomeningitis (LCMV) - - - Parvovirus del riñón (MKPV) + + + Parvovirus de la rata NS1(RMV; RPV; H-1; Kilham) - - - Parvovirus del ratón (MPV) - - - Parvovirus del hámster (HaPV) - - - Rotavirus del ratón (RMV; EDIR) - - - Hantavirus (Hanta) - - - Citomegalovirus (CMV) - - - Virus Tímico del ratón (MTV; MTLV) - - - Virus Polyoma del ratón (PyV; MptV; K virus) - - - Virus Theiler Encefalomielitis del ratón (GDVII; FA) - - + Virus Theiler de la rata (RTV) - - - Reovirus (Reo 1–4) - - + Virus hepatitis del ratón (MHV1-3; JHM; A59) - - - Virus de la Sialodacrioadenitis/ Virus Parker (SDAV, RCV-P) - - - Viruela del ratón, Pox virus (Ectromelia) - - - Table 4 PCR assessment of presence of parasites in samples from experimental C57BL6/N mouse groups with two animal facility origins under distinct housing conditions Parasites PCR Group 1 Filter-top IMEX Group 2 Open IMEX Group 3 Open IBCN Aspiculuris tetraptera - - - Entamoeba spp. - - - Eimeria spp. - - - Demodex spp. - - - Giardia muris - - + Criptosporidium spp. - - + Hymenolepis spp. (H. diminuta, Rodentolepis nana) - - - Encephalitozoon cuniculi - - - Myobia musculi - - - Myocoptes musculinus - - - Notoedres spp. - - - Polyplax spp. - - - Radfordia spp. - - - Psorergates spp. - - - Spironucleus muris - - - Tritrichomonas muris - - - Toxoplasma gondii - - - Syphacia spp. (S. obvelata, S. muris) - - + Sarcoptes scabiei - - - Aspiculuris tetráptera - - - Entamoeba spp. - - - Eimeria spp. - - - RESULTS Colonies from which external mice arrived were certified to be negative for all the microorganism studied. Health monitoring results for the mice born at the IBCN (Group 3) were positive for several bacteria, virus, and parasites (Table 2 – 4 ). All of the bacteria present in this control group, except for the C. kutscheri , were also found in the group of mice originally SPF that were housed in the open cages for 8 to 13 weeks (Group 2; Table 2 ). Concerning the viruses, only 2 out of the 6 present in the facilities were transmitted to the mice in open cages (Table 3), whereas no parasites were detected after 2 or 3 months of sharing the room (Table 4 ). Interestingly, mice housed in the filter top system (Group 1) only recovered 3 bacteria from all the microorganism present in the facilities (Table 2 ). Mice in Groups 1 and 2 were also used as breeders. Although the analysis of reproductive parameters did not reach relevance to be statistically analyzed, performance of mice in either group (i.e. fertility, mice per litter, and weaned mice per mother) was similar independently of the housing system. DISCUSSION Whereas mice in breeding facilities are usually reared free of specific pathogen, the microbiological status of animals in experimental conditions is more difficult to maintain as they are in contact with users, different equipment or apparatus, and may spend time outside their cages. In this study we analyzed the microbiological profile of SPF mice allocated in filter-top cages but sharing the room with mice contaminated with several bacteria, viruses, and parasites. Although no sophisticated extra procedures were put into practice, the filter-top cages were proved to control transmission of viruses, parasites, and most of the bacteria after at least, 8 weeks of sharing the room with conventional mice. Up to our knowledge, this is the first work that analyzes a complete panel of microorganisms to evaluate the efficacy of filter top cages to prevent cross contamination. As latent or inapparent infections, can have a considerable impact on experimental outcomes ( 11 ), this housing system can help to maintain an optimal microbiological status while conducting research in facilities in which animals are positive for a list of microorganisms. By minimizing cross contamination between cages, we were able to improve the welfare of the mice employed and thus, refine our experimental procedures. In our case, this is of particular interest as certain microorganisms like Theiloviruses, Limphocytic Choriomeningitis virus, pinworms, and mites have been demonstrated to specifically affect research on neuroscience by either directly targeting the nervous system or indirectly inducing stress and anxiety. In addition, other microorganism like Pneumonia Virus of mice, Mycoplasma pulmonis , Pasteurella multocida , Streptobacillus moniliformis , pinworns, and intestinal protozoa present at a level that render animals clinically ill, prevents animals from being used in experimental research ( 16 ). Concerning the pathogens found in the health report of mice born at our facility, some of them like Corynebacterium bovis , Pneumocystis spp. , Astrovirus, and Norovirus, are only opportunistic and do not represent a risk in immunocompetent mice. We conclude that filter-top cages could be an easy approach to maintain “clean” experimental mice in environments with circulation of pathogens. The use of IVC combined with change stations may be the optimal way to avoid cross contamination as well as allergen exposure ( 17 ), but this equipment requires specific design of the facilities and have a high startup cost, not always affordable by institutional budgets. On the other hand, filter top cages handled in change stations has been demonstrated to efficiently prevent contamination of most viruses and parasites ( 18 ). When the first filter top cages came to light, they have been also proved effective in reducing airborne allergen levels ( 19 , 20 ), but several reports indicated that accumulation of the waste gases carbon dioxide (CO 2 ) and ammonia (NH 3 ) could occur ( 21 ). To avoid accumulation of these gases, we increase the frequency of bedding change, i.e. twice a week, and adopt low animal density in the cages. In addition, filter-top vendor claims that due to the large filtration area of the filter top systems that we employed, the filter tops maintain an efficient gaseous interchange with the external environment, resulting in lower levels of intra-cage NH3 and CO2. Indeed, all along the experiment, animals were checked daily and no signs of distress were detected nor we do smell ammonium. Although filter tops have been developed to control the quality of the air in the microenvironment, no studies have been published to date that show the effectiveness of limiting transmission of pathogens in long-term trials with mice. All in all, our results show that using filter top cages for long periods of time may be a refinement tool when experimental mice of different microbiological status need to share the room. As infections, apparent or inapparent, may confound scientific results and increase the number of animals used, the screening of affordable refinement techniques to improve animal welfare adds a plus to animal experimentation. Declarations DATA AVAILABILITY All data reported in this article, particularly the Health Monitoring Reports, can be accessed by emailing to Silvina Diaz, at [email protected] FUNDING This work has been supported by grants to SLD from the Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT, PICT 2019-039841859); Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET, PIP-11220130100157CO) References U.S. Department of Health, Education and Welfare PHS. Guide for laboratory animal facilities and care, Inst Lab Anim Resour, 1963. Kraft LM. Observations on the control and natural history of epidemic diarrhea of infant mice (EDIM). Yale J Biol Med 1958; 31: 121–37. AALAS. 50 Years of Laboratory Animal Science, 1999. Gamble MR, Clough G. Ammonia build-up in animal boxes and its effect on rat tracheal epithelium. Lab Anim 1976; 10: 93–104. Broderson JR, Lindsey JR, Crawford JE. The role of environmental ammonia in respiratory mycoplasmosis of rats. Am J Pathol 1976; 85: 115–30. Schoeb TR, Davidson MK, Lindsey JR. Intracage ammonia promotes growth of Mycoplasma pulmonis in the respiratory tract of rats. Infect Immun 1982; 38: 212–7. Booth JL, Umstead TM, Hu S, Dybvig KF, et al. Housing conditions modulate the severity of Mycoplasma pulmonis infection in mice deficient in class A scavenger receptor. Comp Med 2014; 64: 424–39. Dole VS, Henderson KS, Fister RD, et al. Pathogenicity and genetic variation of 3 strains of Corynebacterium bovis in immunodeficient mice. J Am Assoc Lab Anim Sci 2013; 52: 458–66. Macy JD, Cameron GA, Ellis SL, et al. Assessment of static isolator cages with automatic watering when used with conventional husbandry techniques as a factor in the transmission of mouse hepatitis virus. Contemp Top Lab Anim Sci 2002; 41: 30–5. Lipman NS, Corning BF, Saifuddin. Evaluation of isolator caging systems for protection of mice against challenge with mouse hepatitis virus. Lab Anim 1993; 27: 134–40. Mähler M, Berar M, Feinstein R, et al. FELASA recommendations for the health monitoring of mouse, rat, hamster, guinea pig and rabbit colonies in breeding and experimental units. Lab Anim 2014; 48: 178–92. Logge W, Kingham J, Karl T. Behavioural consequences of IVC cages on male and female C57BL/6J mice. Neuroscience 2013; 237: 285–93. Logge W, Kingham J, Karl T. Do individually ventilated cage systems generate a problem for genetic mouse model research? Genes, Brain Behav 2014; 13: 713–20. Guerra S, Chung R, Yerbury J, et al. Behavioural effects of cage systems on the G93A Superoxide Dismutase 1 transgenic mouse model for amyotrophic lateral sclerosis. Genes, Brain Behav 2021; 20: 1–12. Albers TM, Henderson KS, Mulder GB, et al. Pathogen Prevalence Estimates and Diagnostic Methodology Trends in Laboratory Mice and Rats from 2003 to 2020. J Am Assoc Lab Anim Sci 2023; 62: 229–42. Charles River Laboratories. Infectious Agent Technical Information, https://www.criver.com/products-services/research-models-services/animal-health-surveillance/infectious-agent-information?region=3701. (2024, accessed 24 January 2024) Feistenauer S, Sander I, Schmidt J, et al. Influence of 5 different caging types and the use of cage-changing stations on mouse allergen exposure. J Am Assoc Lab Anim Sci 2014; 53: 356–63. Wiese E, Maurer S, Steige G, et al. Decontamination of a barrier facility using microisolator cages and provisional partitioning. Lab Anim 2007; 36: 31–5. Gordon S, Tee RD, Lowson D, et al. Reduction of airborne allergenic urinary proteins from Laboratory Rats. British Journal of Industrial Medicine 1992; 49: 416-422. Hollander A, Heederik D, Doekes G, et al. Determinants of airborne rat and mouse urinary allergen exposure. Scand J Work Environ Heal 1998; 24: 228–35. Lipman NS, Corningl BF, Coiro MA. The effects of intracage ventilation on micro environmental conditions in filter-top cages. Lab Animals 1992; 206–10. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editor assigned by journal 26 Jul, 2024 Submission checks completed at journal 26 Jul, 2024 First submitted to journal 24 Jul, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4797394","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":332380136,"identity":"5216af81-a112-4394-82d1-3f0a3ba6f579","order_by":0,"name":"Daniela R Montagna","email":"","orcid":"","institution":"Universidad de Buenos Aires","correspondingAuthor":false,"prefix":"","firstName":"Daniela","middleName":"R","lastName":"Montagna","suffix":""},{"id":332380137,"identity":"659b8eea-5ec7-497e-8472-68c86ead4dc4","order_by":1,"name":"Karen M Stefani","email":"","orcid":"","institution":"Universidad de Buenos Aires","correspondingAuthor":false,"prefix":"","firstName":"Karen","middleName":"M","lastName":"Stefani","suffix":""},{"id":332380139,"identity":"303c270b-ac01-4116-89a3-0bd6a7d088f9","order_by":2,"name":"Johana Almirón","email":"","orcid":"","institution":"Universidad Nacional de La Plata","correspondingAuthor":false,"prefix":"","firstName":"Johana","middleName":"","lastName":"Almirón","suffix":""},{"id":332380140,"identity":"e66cefcf-7c70-4b80-99a9-c1961e9ce7d1","order_by":3,"name":"Martin Carriquiriborde","email":"","orcid":"","institution":"Universidad Nacional de La Plata","correspondingAuthor":false,"prefix":"","firstName":"Martin","middleName":"","lastName":"Carriquiriborde","suffix":""},{"id":332380143,"identity":"70775385-f2e9-41de-b835-0ab50c1fb462","order_by":4,"name":"Juan M Laborde","email":"","orcid":"","institution":"Universidad Nacional de La Plata","correspondingAuthor":false,"prefix":"","firstName":"Juan","middleName":"M","lastName":"Laborde","suffix":""},{"id":332380144,"identity":"22d70b22-ad0f-4b26-8d4c-8647c09fd0df","order_by":5,"name":"Silvina L Diaz","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABE0lEQVRIie2SPUsDMRjHEwJ3y8Pdel2uXyFHJ+HoZzEU4qIuHS2YcpAupa7d/BAujpUHeoviVzgRnCMuVTr42KPIQfBlE8kPnpC3H/88EMYCgb+IEIYdfkyQylFF3yv8U+HLVqGtL9mfr0iH7paf/ozb7OF6yJJaPL6Uk/I0ibFu2FupTHzX+BSJpKjbEethJAfHaz2OQCvDFzTAkfQqgldSWUEuk6MTg8pmUBg+xwFj2v+waqeckxI7PNgp6XOrpE/+ZpBPG2UpAqGoeJtC7W8wZ5k/RbZKDT2EMZ+vtbKgi6UyOo8yf0r/Alc3r/YsT+7rK7eZlOpyho1z2xLS1J+yB7pLZX/yDbpsf3k/EAgE/jPvqcFcmaU1GesAAAAASUVORK5CYII=","orcid":"","institution":"Universidad de Buenos Aires","correspondingAuthor":true,"prefix":"","firstName":"Silvina","middleName":"L","lastName":"Diaz","suffix":""}],"badges":[],"createdAt":"2024-07-24 18:45:29","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4797394/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4797394/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":63012513,"identity":"e97cf98b-42d5-4a4c-98a7-f2250a7a6b05","added_by":"auto","created_at":"2024-08-22 06:02:44","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":612590,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4797394/v1/4c9f8ac9-aa0e-4474-b5f1-a2fa1811d468.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Efficacy of filter top cages to reduce cross-contamination in mice housed in experimental facilities","fulltext":[{"header":"Introduction","content":"\u003cp\u003eFrom the first wooden and glass cages used to house laboratory mice to the modern individual ventilated cages (IVC), the design of mice microenvironment has evolved to promote animals\u0026rsquo; physical comfort as well as to enable effective sanitary maintenance (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). A milestone in laboratory animal science took place in 1958, when transmission of epidemic diarrhea of infant mice was controlled by housing mice in cages fashioned of galvanized wire mesh covered with fiberglass insulation serving as a passive air filter (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). This principle was improved in several ways until the first transparent plastic shoebox with filter paper inserts on the top, commercially available in 1982 (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). Although this type of cage allows to keep filtered air inside the cage, some reports warned against increases of ammonia levels in cage environments (\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). Therefore, these microisolation cages were then placed on mass air displacement racks, improving the microenvironment parameters. The ultimate step in housing conditions was provided by the positive, individually ventilated microisolation caging system, in which the air is actively filtered before going into the cages. Most modern breeding facilities employs IVC to house mice colonies, but this is not always warranted in experimental facilities.\u003c/p\u003e \u003cp\u003eSince the landing of these modern types of housing systems, several studies evaluated their efficacy to prevent contamination of particular virus and bacteria, with results varying depending on the type of agent. Proliferation of Mycoplasma pulmonis in the lungs of mice experimentally infected was not significantly different between filter-top cages and IVC (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). Another study showed no alteration in morbidity caused by Corynebacterium bovis in immunodeficient mice housed either in filter-top or wire-top cages (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). On the contrary, a partial effect of filter-top cages in preventing transmission of Mouse Hepatitis Virus (MHV) among mice was demonstrated (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Likewise, transmission of MHV after 8 weeks of exposition to open cages with infected animals, was verified in mice housed in open cages, whereas only mice in 2 out of 10 filter-top cages seroconverted, and no mouse housed in IVC was positive (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). To analyze these different reports, it is important to consider that, beside the housing system, husbandry techniques may substantially differ among facilities, influencing the final results. Remarkably, no report has been published up to now, comparing the microbiological status of animals housed in different enclosures.\u003c/p\u003e \u003cp\u003eThe health status of experimental animals is critical, not only for welfare concerns, but also, because microorganisms present in laboratory animals, even at a subclinical level, can widely affect experimental results (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Several reports point to specific alterations in the neurobehavioural phenotype of laboratory mice depending on the housing system. Indeed, it is not surprising that the microenvironment can modify experimental results given its direct influence on the behavior of enclosed animals. C57BL/6JArc mice of either sex, raised in IVC systems showed more anxious-like behaviors in the elevated plus maze, and were socially more active than mice housed in the classic filter-top cages (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). The same laboratory demonstrated that schizophrenia-relevant endophenotypes previously validated in transgenic mice housed in filter-top cages were altered when mice were allocated in IVC housing (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). Another study in a transgenic mouse model for amyotrophic lateral sclerosis found that although central behavioural deficits were evident in both types of housing, responses were (moderately) impacted by IVC housing compared with filter-top cages (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). Therefore, although IVC housing improved the control of microorganism transmission, alterations on behavioral traits were also described.\u003c/p\u003e \u003cp\u003eThe use of mice of known microbiological status is key to ensuring reproducibility of experimental results. Nevertheless, it is not always possible to keep the microbiological status of animals along the experimental procedures, even more when procedures last weeks or months. Contamination of experimental animals can be minimized by employing biosecurity measures, following standardized operative procedures, and maintaining equipment sanitation, and personal hygiene routines. Our laboratory is devoted to the field of neuroscience, conducting behavioral, neurochemical, and histological assays in the experimental facilities of our Institute. Given that this experimental facility receives mice from different vendors or laboratories, and that animals are housed in open cages, it is difficult to keep mice free of infectious agents. We define, therefore, a refinement strategy that could lead to minimize the possibility of cross contamination, by employing filter-top cages. SPF-certified mice were brought to our institutional facility and a health monitoring was conducted 2\u0026ndash;3 months later, proving that the strategy was effective in limiting contamination, specifically for viruses and parasites.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\"\u003e\n \u003ch2\u003eAnimals\u003c/h2\u003e\n \u003cp\u003eTwenty-seven mice were used for the whole study. All of the animals were involved in unrelated, non-invasive studies, mainly as breeders. Fifteen male and female C57BL6/N elite mice were purchased at the Instituto de Medicina Experimental, (IMEX) Academia Nacional de Medicina, Buenos Aires, Argentina. The remaining 12 mice, were male and female C57BL6/N mice born at the facilities of the Instituto de Biolog\u0026iacute;a Celular y Neurociencia (IBCN), Facultad de Medicina, Universidad de Buenos Aires. Experiments on animals were conducted according to local regulations and were approved by the Institutional Ethical Committee (UBA Resol. 1848/2023 FMED). Seven week-old mice, bred in barrier-conditions to maintain an SPF status (as certified by Charles River), were transported in environmental controlled conditions from the IMEX to our institute animal facilities. When arrived, a group of mice (n\u0026thinsp;=\u0026thinsp;6) were immediately housed in 1284L Eurostandard Type II Long (365 x 207 x 140 mm) Tecniplast microisolator cages with filter tops covered with polyester filter sheets (atmospheric dust efficiency of 92% on 8\u0026ndash;10 um particles) whereas another group (n\u0026thinsp;=\u0026thinsp;9) were housed in the same cage model but without the filter-top (two to three mice per cage). Mice stayed isolated for a week in the quarantine room before moving to the stock room, where they shared racks with mice involved in other experimental protocols. Animals were maintained under controlled conditions, i.e., 22\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C room temperature, 60% relative humidity, 12\u0026ndash;12 h light\u0026ndash;dark cycle (lights on at 7.00 am). Mice received ad libitum pelleted food for rodents (Cooperaci\u0026oacute;n) and tap water. White pine shavings were used as bedding and 8\u0026ndash;10 g of tissue paper was added as nesting material in all the cages. Some of these mice were used as breeders, and their litter employ in other projects. The 12 mice born at the IBCN facilities were used in different experiments or as breeders and were housed in polycarbonate open cages (300 x 200 x 140 mm).\u003c/p\u003e\n \u003cp\u003eExternal animals were provided with a health monitoring recently obtained from Charles River corresponding to the molecular diagnostic by polymerase chain reaction (PCR) assays covering several pathogen-specific genomic sequences, all of which were negative. The IBCN facilities regularly receives animals from different vendors or research facilities, and no routine health monitoring is done. However, arriving animals must bring their corresponding health monitoring report and they remain in the quarantine room for one week under observation of technical staff. These facilities do not breed mice, except from certain transgenic lines.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\"\u003e\n \u003ch2\u003eRoutine procedures\u003c/h2\u003e\n \u003cp\u003eMice housed in the microisolators (with or without filter-tops) were exclusively manipulated by the researchers in charge, and the technical staff of the facility was never in contact with these animals. Cages were changed twice weekly, manipulating filter-top cages first and then, the open ones. Additionally, cages were opened once a day every day when female breeders were pregnant or give birth. Microisolators were not changed inside a changing station, but on a bench. Personnel manipulating mice wore lab coats, gloves, face masks, and head covers as personal protective elements. Bedding and nesting material were autoclaved at 134\u0026ordm;C for 10 minutes. Cages and bottles were manually washed with detergent and disinfected with bleach or ammonium (alternating every month). Filter sheets were washed with detergent and disinfected with bleach only once, at the beginning of the experiment. Food and tap water did not receive any decontainment treatment.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\"\u003e\n \u003ch2\u003eExperimental Procedures\u003c/h2\u003e\n \u003cp\u003eExperimental groups were defined as follows: Group 1: external SPF mice housed in filter-top cages; Group 2: external SPF mice housed in open cages; Group 3: conventional mice born at our facilities housed in open cages (Table \u003cspan\u003e1\u003c/span\u003e). External SPF mice stayed in our facility between 8 and 13 weeks, whereas mice born at our own facility were between 8 week- and 1 year-old (Table \u003cspan\u003e1\u003c/span\u003e) at the moment we used them. At the end of the experiment, animals were killed by cervical dislocation and samples were immediately collected from the lungs, salivary glands, liver, spleen, and cecum. Fresh stool was also recovered from the rectum. Samples were kept at -60\u0026deg;C until shipping for microbiological analysis. Samples from mice of the same experimental group obtained at different time points were pooled for the microbiological analysis in 3 different tubes: (\u003cspan\u003e1\u003c/span\u003e) feces, (\u003cspan\u003e2\u003c/span\u003e) cecum, and (\u003cspan\u003e3\u003c/span\u003e) the 4 other organs as requested by the Laboratorio de Animales de Experimentaci\u0026oacute;n (LAE), Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, the national reference center where the health monitoring was conducted. Following international recommendations (\u003cspan\u003e11\u003c/span\u003e) and international (\u003cspan\u003e15\u003c/span\u003e) and local prevalence of microorganisms, several bacteria, viruses, and parasites, as shown in Tables \u003cspan\u003e2\u003c/span\u003e to \u003cspan\u003e4\u003c/span\u003e, were evaluated by PCR testing, a technique known by its high specificity and sensitivity. The microbial status of external mice was not confirmed upon receipt.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 1\u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"6\"\u003e\n \u003cp\u003e\u003cem\u003eOrigin animal facility, sex, age, and housing conditions of experimental C57BL6/N mouse groups\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eExperimental group\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOrigin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTime at IBCN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCage type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSex\u003c/p\u003e\n \u003cp\u003e(M: F)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFilter-top\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3:0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFilter-top\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0:3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOpen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3:2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOpen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0:4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIBCN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8\u0026ndash;12 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOpen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1:5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8\u0026ndash;12 weeks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIBCN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1 year\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOpen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3:3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1 year\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 2\u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003e\u003cem\u003ePCR assessment of bacterial presence in samples from experimental C57BL6/N mouse groups with two animal facility origins under distinct housing conditions\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eBacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003ePCR\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup 1\u003c/p\u003e\n \u003cp\u003eFilter-top IMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup 2\u003c/p\u003e\n \u003cp\u003eOpen IMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup 3\u003c/p\u003e\n \u003cp\u003eOpen IBCN\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eBordetella bronchiseptica\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eBordetella pseudohinzzi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eFilobacterium rodentium (CAR bacillus)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eCitrobacter rodentium\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eCampilobacter spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eClostridium piliforme\u003c/em\u003e (Tyzzer)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eFrancisella tularensis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eCorynebacterium bovis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eCorynebacterium kutscheri\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eHelicobacter spp (H. hepaticus; H. bilis; H. rappini)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eKlebsiella oxytoca\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eKlebsiella pneumoniae\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eRodentibacter spp. (R. heylii; R. pneumotropicus; R. ratti) (ex-Pasteurella pneumotropica)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eMycoplasma pulmonis.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eLeptospira spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eListeria monocytogenes\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eProteus mirabilis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ePneumocysitis spp. (P, carinii; P. mutina)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eSalmonella spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eShigella spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eStaphilococcus aureus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eStreptococcus pneumoniae\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eStreptococcus Beta hemol\u0026iacute;tico\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eStreptobacillus moniliformis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eTable\u0026nbsp;3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003e\u003cem\u003ePCR assessment of viral presence in samples from experimental C57BL6/N mouse groups with two animal facility origins under distinct housing conditions\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eVirus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003ePCR\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup 1\u003c/p\u003e\n \u003cp\u003eFilter-top IMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup 2\u003c/p\u003e\n \u003cp\u003eOpen IMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eGroup 3\u003c/p\u003e\n \u003cp\u003eOpen IBCN\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAdenovius (MAd-1; MAd-2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus de la Pneumon\u0026iacute;a (PVM)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAstrovirus del rat\u0026oacute;n (AstV tipo 1\u0026ndash;2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus Sendai (SeV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNorovirus murino (MNV 1\u0026ndash;4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus diminuto del rat\u0026oacute;n (MVM)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus Elevador de la Lactatodeshidrogenasa (LDH)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus de la linfocoriomeningitis (LCMV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eParvovirus del ri\u0026ntilde;\u0026oacute;n (MKPV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eParvovirus de la rata NS1(RMV; RPV; H-1; Kilham)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eParvovirus del rat\u0026oacute;n (MPV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eParvovirus del h\u0026aacute;mster (HaPV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRotavirus del rat\u0026oacute;n (RMV; EDIR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHantavirus (Hanta)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCitomegalovirus (CMV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus T\u0026iacute;mico del rat\u0026oacute;n (MTV; MTLV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus Polyoma del rat\u0026oacute;n (PyV; MptV; K virus)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus Theiler Encefalomielitis del rat\u0026oacute;n (GDVII; FA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus Theiler de la rata (RTV)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReovirus (Reo 1\u0026ndash;4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus hepatitis del rat\u0026oacute;n (MHV1-3; JHM; A59)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVirus de la Sialodacrioadenitis/ Virus Parker (SDAV, RCV-P)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eViruela del rat\u0026oacute;n, Pox virus (Ectromelia)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv\u003e\n \u003cdiv align=\"left\"\u003eTable 4\u003c/div\u003e\n \u003ctable id=\"Taba\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003e\u003cem\u003ePCR assessment of presence of parasites in samples from experimental C57BL6/N mouse groups with two animal facility origins under distinct housing conditions\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eParasites\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003ePCR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup 1\u003c/p\u003e\n \u003cp\u003eFilter-top IMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup 2\u003c/p\u003e\n \u003cp\u003eOpen IMEX\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup 3\u003c/p\u003e\n \u003cp\u003eOpen IBCN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eAspiculuris tetraptera\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eEntamoeba spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eEimeria spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eDemodex spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eGiardia muris\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eCriptosporidium spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eHymenolepis spp. (H. diminuta, Rodentolepis nana)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eEncephalitozoon cuniculi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eMyobia musculi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eMyocoptes musculinus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eNotoedres spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ePolyplax spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eRadfordia spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ePsorergates spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eSpironucleus muris\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eTritrichomonas muris\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eToxoplasma gondii\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eSyphacia spp. (S. obvelata, S. muris)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eSarcoptes scabiei\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eAspiculuris tetr\u0026aacute;ptera\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eEntamoeba spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eEimeria spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eColonies from which external mice arrived were certified to be negative for all the microorganism studied. Health monitoring results for the mice born at the IBCN (Group 3) were positive for several bacteria, virus, and parasites (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e4\u003c/span\u003e). All of the bacteria present in this control group, except for the \u003cem\u003eC. kutscheri\u003c/em\u003e, were also found in the group of mice originally SPF that were housed in the open cages for 8 to 13 weeks (Group 2; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Concerning the viruses, only 2 out of the 6 present in the facilities were transmitted to the mice in open cages (Table\u0026nbsp;3), whereas no parasites were detected after 2 or 3 months of sharing the room (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Interestingly, mice housed in the filter top system (Group 1) only recovered 3 bacteria from all the microorganism present in the facilities (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMice in Groups 1 and 2 were also used as breeders. Although the analysis of reproductive parameters did not reach relevance to be statistically analyzed, performance of mice in either group (i.e. fertility, mice per litter, and weaned mice per mother) was similar independently of the housing system.\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eWhereas mice in breeding facilities are usually reared free of specific pathogen, the microbiological status of animals in experimental conditions is more difficult to maintain as they are in contact with users, different equipment or apparatus, and may spend time outside their cages. In this study we analyzed the microbiological profile of SPF mice allocated in filter-top cages but sharing the room with mice contaminated with several bacteria, viruses, and parasites. Although no sophisticated extra procedures were put into practice, the filter-top cages were proved to control transmission of viruses, parasites, and most of the bacteria after at least, 8 weeks of sharing the room with conventional mice. Up to our knowledge, this is the first work that analyzes a complete panel of microorganisms to evaluate the efficacy of filter top cages to prevent cross contamination. As latent or inapparent infections, can have a considerable impact on experimental outcomes (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e), this housing system can help to maintain an optimal microbiological status while conducting research in facilities in which animals are positive for a list of microorganisms. By minimizing cross contamination between cages, we were able to improve the welfare of the mice employed and thus, refine our experimental procedures. In our case, this is of particular interest as certain microorganisms like Theiloviruses, Limphocytic Choriomeningitis virus, pinworms, and mites have been demonstrated to specifically affect research on neuroscience by either directly targeting the nervous system or indirectly inducing stress and anxiety. In addition, other microorganism like Pneumonia Virus of mice, \u003cem\u003eMycoplasma pulmonis\u003c/em\u003e, \u003cem\u003ePasteurella multocida\u003c/em\u003e, \u003cem\u003eStreptobacillus moniliformis\u003c/em\u003e, pinworns, and intestinal protozoa present at a level that render animals clinically ill, prevents animals from being used in experimental research (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Concerning the pathogens found in the health report of mice born at our facility, some of them like \u003cem\u003eCorynebacterium bovis\u003c/em\u003e, \u003cem\u003ePneumocystis spp.\u003c/em\u003e, Astrovirus, and Norovirus, are only opportunistic and do not represent a risk in immunocompetent mice. We conclude that filter-top cages could be an easy approach to maintain “clean” experimental mice in environments with circulation of pathogens.\u003c/p\u003e \u003cp\u003eThe use of IVC combined with change stations may be the optimal way to avoid cross contamination as well as allergen exposure (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e), but this equipment requires specific design of the facilities and have a high startup cost, not always affordable by institutional budgets. On the other hand, filter top cages handled in change stations has been demonstrated to efficiently prevent contamination of most viruses and parasites (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). When the first filter top cages came to light, they have been also proved effective in reducing airborne allergen levels (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e), but several reports indicated that accumulation of the waste gases carbon dioxide (CO\u003csub\u003e2\u003c/sub\u003e) and ammonia (NH\u003csub\u003e3\u003c/sub\u003e) could occur (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). To avoid accumulation of these gases, we increase the frequency of bedding change, i.e. twice a week, and adopt low animal density in the cages. In addition, filter-top vendor claims that due to the large filtration area of the filter top systems that we employed, the filter tops maintain an efficient gaseous interchange with the external environment, resulting in lower levels of intra-cage NH3 and CO2. Indeed, all along the experiment, animals were checked daily and no signs of distress were detected nor we do smell ammonium.\u003c/p\u003e \u003cp\u003eAlthough filter tops have been developed to control the quality of the air in the microenvironment, no studies have been published to date that show the effectiveness of limiting transmission of pathogens in long-term trials with mice. All in all, our results show that using filter top cages for long periods of time may be a refinement tool when experimental mice of different microbiological status need to share the room. As infections, apparent or inapparent, may confound scientific results and increase the number of animals used, the screening of affordable refinement techniques to improve animal welfare adds a plus to animal experimentation.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDATA AVAILABILITY\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data reported in this article, particularly the Health Monitoring Reports, can be accessed by emailing to Silvina Diaz, at [email protected]\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eFUNDING\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work has been supported by grants to SLD from the\u003cem\u003e\u0026nbsp;Agencia Nacional de Promoci\u0026oacute;n Cient\u0026iacute;fica y Tecnol\u0026oacute;gica\u0026nbsp;\u003c/em\u003e(ANPCyT,\u003cem\u003e\u0026nbsp;\u003c/em\u003ePICT 2019-039841859); \u003cem\u003eConsejo Nacional de Investigaciones Cient\u0026iacute;ficas y Tecnol\u0026oacute;gicas\u003c/em\u003e (CONICET, PIP-11220130100157CO)\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eU.S. Department of Health, Education and Welfare PHS. 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FELASA recommendations for the health monitoring of mouse, rat, hamster, guinea pig and rabbit colonies in breeding and experimental units. Lab Anim 2014; 48: 178\u0026ndash;92. \u003c/li\u003e\n\u003cli\u003eLogge W, Kingham J, Karl T. Behavioural consequences of IVC cages on male and female C57BL/6J mice. Neuroscience 2013; 237: 285\u0026ndash;93. \u003c/li\u003e\n\u003cli\u003eLogge W, Kingham J, Karl T. Do individually ventilated cage systems generate a problem for genetic mouse model research? Genes, Brain Behav 2014; 13: 713\u0026ndash;20. \u003c/li\u003e\n\u003cli\u003eGuerra S, Chung R, Yerbury J, et al. Behavioural effects of cage systems on the G93A Superoxide Dismutase 1 transgenic mouse model for amyotrophic lateral sclerosis. Genes, Brain Behav 2021; 20: 1\u0026ndash;12.\u003c/li\u003e\n\u003cli\u003eAlbers TM, Henderson KS, Mulder GB, et al. Pathogen Prevalence Estimates and Diagnostic Methodology Trends in Laboratory Mice and Rats from 2003 to 2020. J Am Assoc Lab Anim Sci 2023; 62: 229\u0026ndash;42. \u003c/li\u003e\n\u003cli\u003eCharles River Laboratories. Infectious Agent Technical Information, https://www.criver.com/products-services/research-models-services/animal-health-surveillance/infectious-agent-information?region=3701. (2024, accessed 24 January 2024)\u003c/li\u003e\n\u003cli\u003eFeistenauer S, Sander I, Schmidt J, et al. Influence of 5 different caging types and the use of cage-changing stations on mouse allergen exposure. J Am Assoc Lab Anim Sci 2014; 53: 356\u0026ndash;63. \u003c/li\u003e\n\u003cli\u003eWiese E, Maurer S, Steige G, et al. Decontamination of a barrier facility using microisolator cages and provisional partitioning. Lab Anim 2007; 36: 31\u0026ndash;5. \u003c/li\u003e\n\u003cli\u003eGordon S, Tee RD, Lowson D, et al. Reduction of airborne allergenic urinary proteins from Laboratory Rats. British Journal of Industrial Medicine 1992; 49: 416-422. \u003c/li\u003e\n\u003cli\u003eHollander A, Heederik D, Doekes G, et al. Determinants of airborne rat and mouse urinary allergen exposure. Scand J Work Environ Heal 1998; 24: 228\u0026ndash;35. \u003c/li\u003e\n\u003cli\u003eLipman NS, Corningl BF, Coiro MA. The effects of intracage ventilation on micro environmental conditions in filter-top cages. Lab Animals 1992; 206\u0026ndash;10. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"archives-of-microbiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"aomi","sideBox":"Learn more about [Archives of Microbiology](https://www.springer.com/journal/203)","snPcode":"203","submissionUrl":"https://submission.nature.com/new-submission/203/3","title":"Archives of Microbiology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4797394/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4797394/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAn optimal microbiological status is key to ensuring reproducible experimental results. However, contamination is difficult to avoid during long experimental procedures when animals spend time outside their enclosures, in contact with users and different equipment. To evaluate the efficacy of filter-top cages to minimize cross contamination when experimental mice of different microbiological status share the same room, we studied a complete panel of microorganisms in mice housed in different systems. C57BL6/N mice were purchased to an SPF facility: one group was housed in filter top cages whereas another group stayed in similar cages but without the filter-top. These external mice shared the room with mice involved in other experimental protocols between 8 and 13 weeks. A group of conventional mice born at our facilities housed in open cages served as control. Samples from different organs were analyzed by PCR. Mice born at the experimental facility were positive for several bacteria, virus, and parasites. All the bacteria present in this control group, were also found in the group of mice originally SPF housed in the open cages. Only 2 out of the 6 viruses present in the facilities were transmitted to the external mice in open cages, whereas no parasites were detected. Interestingly, mice housed in the filter-top system only recovered 3 bacteria from all the microorganism present in the facilities. Our results shown that using filter-top cages for long periods may be a refinement tool when there is no alternative to share the room with mice of different microbiological status.\u003c/p\u003e","manuscriptTitle":"Efficacy of filter top cages to reduce cross-contamination in mice housed in experimental facilities","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-22 05:54:37","doi":"10.21203/rs.3.rs-4797394/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorAssigned","content":"","date":"2024-07-27T01:25:02+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-07-26T14:53:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"Archives of Microbiology","date":"2024-07-24T18:44:17+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"archives-of-microbiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"aomi","sideBox":"Learn more about [Archives of Microbiology](https://www.springer.com/journal/203)","snPcode":"203","submissionUrl":"https://submission.nature.com/new-submission/203/3","title":"Archives of Microbiology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"4295d6c4-a13d-4fa4-8b4e-004f04bdbb3f","owner":[],"postedDate":"August 22nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-08-22T05:54:37+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-22 05:54:37","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4797394","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4797394","identity":"rs-4797394","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}