Evaluation of Etests and the disk diffusion method for assessment of the activity of ceftazidime-avibactam against Enterobacterales and Pseudomonas aeruginosa in China

Evaluation of Etests and the disk diffusion method for assessment of the activity of ceftazidime-avibactam against Enterobacterales and Pseudomonas aeruginosa in China | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research article Evaluation of Etests and the disk diffusion method for assessment of the activity of ceftazidime-avibactam against Enterobacterales and Pseudomonas aeruginosa in China Qi Wang, Feifei Zhang, Zhanwei Wang, Hongbin Chen, Xiaojuan Wang, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-26430/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 29 Jun, 2020 Read the published version in BMC Microbiology → Version 1 posted 4 You are reading this latest preprint version Abstract Background : Gram-negative bacilli, particularly Enterobacterales and Pseudomonas aeruginosa , often acquire antimicrobial resistance. Ceftazidime-avibactam was approved for use in China in 2019. However, currently available commercial antimicrobial susceptibility test kits have not yet been developed. Here, we evaluated the Etest and disk diffusion method for assessment of the efficacy of ceftazidime-avibactam against Enterobacterales and P. aeruginosa in China. Results: In total, 194 Enterobacterales and 77 P. aeruginosa isolates, which were divided into a random selection group (140 Enterobacterales and 54 P. aeruginosa isolates) and a stock group (46 Enterobacterales and 31 P. aeruginosa isolates), were assessed by the Etest, disk diffusion, and broth microdilution (BMD) methods. Minimum inhibitory concentrations (MICs) and zone diameters were interpreted according to the CLSI M100 30 th edition. For all 271 Enterobacterales and P. aeruginosa isolates, no very major errors were found using Etests. The overall categorical agreement rates (CA%) of Etests for Enterobacterales and P. aeruginosa were 99.5% (193/194) and 96.1% (74/77), respectively. The overall essential agreement rates (EA%) of Etests for Enterobacterales and P. aeruginosa were 95.9% (186/194) and 94.8% (73/77), respectively. In both the random selection and stock groups, EA% and CA% values of Etests exceeded 90%. Overall CA% values of the disk diffusion method for Enterobacterales and P. aeruginosa were 98.5% (191/194) and 93.5% (71/77), respectively. There was no linear relationship between zone diameter and BMD MIC. Conclusions: For Enterobacterales and P. aeruginosa , Etests and the disk diffusion method could have better performance as alternative methods to meet the needs of clinical treatment interpretation. Application of the disk diffusion method in Enterobacterales was superior to that in P. aeruginosa . Applied & Industrial Microbiology General Microbiology broth microdilution disk diffusion Etest ceftazidime-avibactam Figures Figure 1 Figure 2 Figure 3 Figure 4 Background Gram-negative bacilli, particularly carbapenem-resistant Enterobacterales (CRE) and Pseudomonas aeruginosa , exhibit major antimicrobial resistance worldwide, including in European countries, the United States of America (USA), and China [1–3]. The approval of ceftazidime-avibactam for clinical use in Europe and the USA has brought new treatment options to CRE-infected patients, particularly those with serine-carbapenemase resistance mechanisms [4, 5]. Ceftazidime-avibactam was approved for use in China in 2019. However, currently available commercial antimicrobial susceptibility test kits have not yet been developed for analysis of ceftazidime-avibactam resistance in China, and in patients with infections caused by CRE, which are resistant to multiple antimicrobials, the results of ceftazidime-avibactam susceptibility tests are urgently needed to facilitate appropriate targeted treatment. Although ceftazidime-avibactam has excellent in vitro activity against carbapenem-resistant Klebsiella pneumoniae (CRKP) and Pseudomonas aeruginosa strains, a small number of resistant strains will still appear during treatment [6–8]. Therefore, susceptibility test results for ceftazidime-avibactam are even more critical. In most of the laboratories in China, performing the standard broth microdilution method (BMD) is challenging. Therefore, other rapid, simple methods are required as alternatives to determine ceftazidime-avibactam susceptibility. In this study, we evaluated two antimicrobial susceptibility test methods for ceftazidime-avibactam, i.e., the Etest method and the disk diffusion method with the standard BMD, to evaluate whether these easy-to-use methods could replace standard methods when required in the clinical setting. Materials And Methods Groups Isolates were divided into two groups, i.e., the random selection group and the stock group. For the random selection group, we randomly selected 140 Enterobacterales and 46 Pseudomonas aeruginosa strains from clinical nonrepeated isolates obtained at Peking University People’s Hospital. Among these samples, 59.3% (83/140) of Enterobacterales and 56.5% (26/46) of Pseudomonas aeruginosa strains were defined as fresh strains from clinical isolates obtained within 1 month prior to testing (November 2019 to March 2020). The remaining strains in the random selection group were obtained from the strain repository of Peking University People’s Hospital from January 2018 to October 2019. The 140 strains of Enterobacterales used in the testing included 13 species, i.e., 25 K. pneumoniae , 19 Escherichia coli , 18 Proteus mirabilis , 17 Enterobacter cloacae , 16 Serratia marcescens , 15 Citrobacter freundii , 14 K. oxytoca , four Proteus vulgaris , three Morganella morganii , three Providencia stuartii , two Providencia rettgeri , two K. aerogenes , and two Citrobacter koseri strains. For the stock group, we selected 54 strains of Enterobacterales from 15 hospitals in the CRE China-Network from January 2015 to October 2019 and requested that the minimum inhibitory concentration (MIC) of ceftazidime-avibactam be between 2 and 256 µg/mL. Among these strains, six strains (11.1%) showed MICs for ceftazidime-avibactam of between 8 and 16 µg/mL, and 15 strains (27.8%) showed MIC between 4 and 32 µg/mL. The carbapenem-resistance genes present in these strains were elucidated in previous studies [9]. The 54 strains of Enterobacterales used in this study included 29 K. pneumoniae (18 strains having the bla KPC gene and 10 strains having the bla NDM gene), 12 Escherichia coli (two strains having the bla KPC gene and seven strains having the bla NDM gene), eight Enterobacter cloacae (one strain having the bla KPC gene, five strains having the bla NDM gene, one strain having the bla IMP gene, and one strain having bla VIM gene), three K. oxytocai (two strains having the bla IMP gene and one strain having the bla NDM gene), and two Citrobacter freundii (one strain having the bla IMP gene and one strain having the bla NDM gene). We selected 31 strains of Pseudomonas aeruginosa from the eight hospitals involved in the CARES 2018 project as stock group strains and required the MIC of ceftazidime-avibactam to be between 2 and 256 µg/mL. Among these strains, 12 strains (38.7%) had MICs for ceftazidime-avibactam between 8 and 16 µg/mL, and 25 strains (80.6%) had MICs between 4 and 32 µg/mL. All strains were removed from a -80 °C ultra-low temperature refrigerator and transferred to Columbia blood agar twice before antimicrobial susceptibility testing. Antimicrobial susceptibility testing For the disk diffusion method, ceftazidime-avibactam disks were obtained from Oxoid (Thermo Scientific, China) The content of ceftazidime-avibactam in each disk was 30 µg/20 µg. The operation process was strictly tested following the requirements of the CLSI standardized method [10]. For the Etest gradient diffusion method, ceftazidime-avibactam Etest strips were obtained from BioMérieux (Marcy l’Etoile, France). The test was performed in strict accordance with the manufacturer’s instructions. The ceftazidime-avibactam concentration gradient ranged from 0.016 to 256 µg/mL. When the Etest MIC value was between the standard value and twice the standard value (0.016, 0.032, 0.064, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128, and 256), the high standard value will be read as the MIC. The MH agar used for both the disk diffusion method and the Etest gradient diffusion method for antimicrobial susceptibility testing was obtained from Oxoid (Thermo Scientific Inc). The BMD was performed strictly following CLSI guidelines [11]. Ceftazidime and avibactam powers were obtained from Pfizer (USA). The concentration ranged from the standard double dilution of 0.016 µg/mL to 256 µg/mL. Quality control and colony counting are performed simultaneously for each batch of experiments. Escherichia coli ATCC 25922, K. pneumoniae ATCC 700603, Escherichia coli ATCC 35218, and Pseudomonas aeruginosa ATCC 27853 were used as experimental quality control strains. The experiment was considered valid only when the experimental values of all the quality control strains were within the acceptable range. The MICs and zone diameters of ceftazidime-avibactam for Enterobacterales and Pseudomonas aeruginosa were interpreted according to CLSI M100 30th edition [11]. Briefly, MICs of less than or equal to 8/4 µg/mL or a zone diameter of greater than or equal to 21 mm indicated that the strain was susceptible, whereas MICs of greater than or equal to 16/4 µg/mL or a zone diameter of less than or equal to 20 mm indicated that the strain was resistant. Essential agreement (EA) indicated that the difference between the MIC value measured by Etest and the BMD did not exceed one dilution factor. Categorical agreement (CA) indicated that the BMD method was consistent with the classification results from the disk diffusion method and Etest method based on the same CLSI breakpoints. Very major errors (VMEs) indicated that the strain was susceptible by Etest or the disk diffusion method but resistant by the BMD. Major errors (MEs) indicated that the strain was susceptible by the BMD but resistant by Etest or the disk diffusion method. Result Etest versus the BMD For 194 Enterobacterales strains, no VMEs were found using the Etest method. As shown in Table 1 , the overall CA rate was 99.5%, and the overall EA rate was 95.9%. The CA rate of the stock group was 90.7%, and the CA rate in the random selection group was 97.9%. When comparing Etest results with BMD results, we found that the MICs of eight strains exceeded the two dilution factors. As shown in Fig. 1 , the Etest MICs of 102 (52.5%) strains were consistent with the BMD MICs. The Etest MICs of 71 (36.6%) strains were a dilution multiple higher than the BMD MICs. Only 12 (6.2%) strains had Etest MICs that were a dilution multiple lower than the BMD MICs. Table 1 Evaluation of essential and categorical agreement between the BMD method and Etests or the disk diffusion method for analysis of ceftazidime-avibactam antimicrobial susceptibility Organisms No. of strains tested Etest Disk diffusion No. of EA EA% No. of CA CA% No. of VMEs No. of MEs No. of CA CA% No. of VMEs No. of MEs Enterobacterales Random selection Group 140 137 97.9% 140 100.0% 0 0 140 100.0% 0 0 Stock group: 54 49 90.7% 53 98.1% 0 1 51 94.4% 2 1 Total in Enterobacterales 194 186 95.9% 193 99.5% 0 1 191 98.5% 2 1 Pseudomonas aeruginosa Random selection Group 46 45 97.8% 46 100.0% 0 0 43 93.5% 0 3 Stock group: 31 28 90.3% 28 90.3% 0 3 29 93.5% 1 1 Total in Pseudomonas aeruginosa 77 73 94.8% 74 96.1% 0 3 72 93.5% 1 4 Total in all tested strains 271 259 95.6% 267 98.5% 0 4 263 97.0% 3 5 EA: essential agreement; CA: categorical agreement; VMEs: very major errors (false susceptible); MEs: major errors (false resistant) For 77 Pseudomonas aeruginosa strains, no VMEs were found using the Etest method. As shown in Table 1 , the overall CA rate was 96.1%, and the overall EA rate was 94.8%. The CA rate in the stock group was 90.3%, and the CA rate in the random selection group was 100%. As shown in Fig. 2 , the Etest MICs of 45 (58.4%) strains were consistent with the MICs obtained by the BMD. The Etest MICs of 22 (28.6%) strains were one dilution higher than those obtained by the BMD, whereas those of six (7.8%) strains were one dilution lower than the MICs obtained by the BMD. For one strain, the Etest MIC was two dilutions higher than those obtained by the BMD. Three MEs appeared in the stock group when the Etest method was used. Disk diffusion method versus BMD A comparison of the disk diffusion method and BMD results for 194 Enterobacterales strains (Fig. 3 ) showed that there were no linear relationships between zone diameter and MIC. The overall CA rate in the 194 Enterobacterales strains was 98.5%. Two VMEs and one ME were found using the disk diffusion method in the stock group; all were for K. pneumoniae strains. No VMEs or MEs were found using the disk diffusion method in the random selection group. There were 22 strains of Enterobacterales with zone diameters of 2 mm (19–22 mm susceptibity breakpoint). Forty-one of the 45 resistant strains obtained by BMD had zone diameters in the range of 13–20 mm. In a comparison of the results of the disk diffusion method and BMD for 77 Pseudomonas aeruginosa strains, the number of MEs was four, and the number of VMEs was 1. As shown in Table 1 , the overall CA rate was 93.5%. Moreover, as shown in Fig. 4 , when the zone diameter was 20 mm, the MICs obtained by the BMD method were 4, 8, 16, or 64 µg/mL. Discussion In the past ten years, the incidence of CRE, particularly CRKP, has increased significantly in China. The latest China Antimicrobial Resistance Surveillance System (CARSS) data show that the incidence of CRKP nationwide is as high as 10.1% ( http://www.carss.cn/Report/Details?aId=648 ). However, few active antibacterial agents, such as tigecycline and colistin, are available to treat CRKP in the clinical setting [12, 13], resulting in high mortality worldwide. Previous molecular epidemiological data show that more than 70% of CRE isolated in China from 2012 to 2016 produce KPC-type carbapenemases [9]. Ceftazidime-avibactam, a drug with potent antibacterial activity against serine-carbapenemase, was approved for use in China in 2019. Recent retrospective studies have shown that ceftazidime-avibactam treatment of CRKP and Pseudomonas aeruginosa infection in patients who have undergone solid organ transplantation improves clinical success rates [14, 15]. Despite these promising findings, ceftazidime-avibactam antimicrobial susceptibility test results are essential for clinical use of this treatment. However, no ceftazidime-avibactam combination kits are available for assessing resistance in China. To the best of our knowledge, this is the first study comparing Etests, the disk diffusion method, and the BMD with regard to detection of ceftazidime-avibactam susceptibility in China. Compared with the standard BMD method, no VMEs were found using the Etest method. The results of Etest MICs and BMD MICs were reasonably well correlated for both Enterobacterales and Pseudomonas aeruginosa . The overall of EA% of 271 tested strains was 95.6%. Compared with the BMD method, the Etest method exhibited an excellent linear correlation, supporting the use of this approach as an alternative to the standard clinical method without considering economic costs. This result was similar to the previous research findings of other authors [16]. The disk diffusion method is easy to implement in the clinical setting from an economic standpoint. The CA% values of the ceftazidime-avibactam disk diffusion method against Enterobacterales and Pseudomonas aeruginosa were 98.5% and 93.5%, respectively, similar to the findings of Shields and other scholars [16, 17]. Indeed, our results showed that application of the disk diffusion method was more appropriate for Enterobacterales than for Pseudomonas aeruginosa . Notably, however, the disk diffusion method did not have an excellent linear correlation with BMD. Therefore, the zone diameters of strains near the breakpoints (± 2 mm) should be checked by the BMD carefully, consistent with other research results [17, 18]. This should also be considered when users refer to the new version of CLSI M100, which suggests using the disk diffusion method [11]. Conclusions In conclusion, for Enterobacterales and Pseudomonas aeruginosa , Etests and the disk diffusion method showed good performance as alternative methods to meet the needs of clinical treatment interpretation. The application of the disk diffusion method was superior for Enterobacterales compared with Pseudomonas aeruginosa . Declarations Ethics approval and consent to participate: Not applicable Consent for publication: Not applicable Competing interests: The authors declare that they have no competing interests Funding: This work was supported by National Natural Science Foundation of China (81625014) Authors' contributions: HW conceived and designed the study. QW, FZ, HC, XW, YZ and SL performed experiments described in this study. QW wrote the draft, and HW revised it. All authors approved the final version. Competing Interests: The authors declare no conflicts of interest in this work. Acknowledgements: We would like to thank Editage (www.editage.cn) for English language editing. References Chinese XDRCWG, Guan X, He L, Hu B, Hu J, Huang X, Lai G, Li Y, Liu Y, Ni Y et al : Laboratory diagnosis, clinical management and infection control of the infections caused by extensively drug-resistant Gram-negative bacilli: a Chinese consensus statement . Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases 2016, 22 Suppl 1 :S15-25. Hu F, Zhu D, Wang F, Wang M: Current Status and Trends of Antibacterial Resistance in China . Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2018, 67 (suppl_2):S128-S134. 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Wang Q, Wang X, Wang J, Ouyang P, Jin C, Wang R, Zhang Y, Jin L, Chen H, Wang Z et al : Phenotypic and Genotypic Characterization of Carbapenem-resistant Enterobacteriaceae: Data From a Longitudinal Large-scale CRE Study in China (2012-2016) . Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2018, 67 (suppl_2):S196-S205. Clinical and Laboratory Standards Institute. 2015. Performance standards for antimicrobial disk susceptibility tests; 12th ed. M02-A12. Clinical and Laboratory Standards Institute, Wayne, PA. CLSI. Performance Standards for Antimicrobial Susceptibility Testing. 30th ed. CLSI supplement M100. Wayne, PA: Clinical and Laboratory Standards Institute; 2020. Tzouvelekis LS, Markogiannakis A, Psichogiou M, Tassios PT, Daikos GL: Carbapenemases in Klebsiella pneumoniae and other Enterobacteriaceae: an evolving crisis of global dimensions . Clinical microbiology reviews 2012, 25 (4):682-707. Gutiérrez-Gutiérrez B, Salamanca E, de Cueto M, Hsueh P-R, Viale P, Paño-Pardo JR, Venditti M, Tumbarello M, Daikos G, Cantón R et al : Effect of appropriate combination therapy on mortality of patients with bloodstream infections due to carbapenemase-producing Enterobacteriaceae (INCREMENT): a retrospective cohort study . The Lancet Infectious Diseases 2017, 17 (7):726-734. Chen W, Sun L, Guo L, Cao B, Liu Y, Zhao L, Lu B, Li B, Chen J, Wang C: Clinical outcomes of ceftazidime-avibactam in lung transplant recipients with infections caused by extensively drug-resistant gram-negative bacilli . Annals of translational medicine 2020, 8 (3):39. Sternbach N, Leibovici Weissman Y, Avni T, Yahav D: Efficacy and safety of ceftazidime/avibactam: a systematic review and meta-analysis . The Journal of antimicrobial chemotherapy 2018, 73 (8):2021-2029. Shields RK, Clancy CJ, Pasculle AW, Press EG, Haidar G, Hao B, Chen L, Kreiswirth BN, Nguyen MH: Verification of Ceftazidime-Avibactam and Ceftolozane-Tazobactam Susceptibility Testing Methods against Carbapenem-Resistant Enterobacteriaceae and Pseudomonas aeruginosa . Journal of clinical microbiology 2018, 56 (2). Sader HS, Rhomberg PR, Chandrasekaran S, Trejo M, Fedler KA, Boyken LD, Diekema DJ: Correlation between Broth Microdilution and Disk Diffusion Results when Testing Ceftazidime-Avibactam against a Challenge Collection of Enterobacterales Isolates: Results from a Multilaboratory Study . Journal of clinical microbiology 2020, 58 (4). Sader HS, Rhomberg PR, Huband MD, Critchley IA, Stone GG, Flamm RK, Jones RN: Assessment of 30/20-Microgram Disk Content versus MIC Results for Ceftazidime-Avibactam Tested against Enterobacteriaceae and Pseudomonas aeruginosa . Journal of clinical microbiology 2018, 56 (6). Cite Share Download PDF Status: Published Journal Publication published 29 Jun, 2020 Read the published version in BMC Microbiology → Version 1 posted Editor assigned by journal 01 May, 2020 First submitted to journal 30 Apr, 2020 Submission checks completed at journal 30 Apr, 2020 Editor invited by journal 30 Apr, 2020 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-26430","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research article","associatedPublications":[],"authors":[{"id":538952,"identity":"f7b00e23-f615-45fd-ba5f-1d4d5090bbe0","order_by":1,"name":"Qi Wang","email":"","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Qi","middleName":"","lastName":"Wang","suffix":""},{"id":538953,"identity":"495f3b64-42b7-4725-9408-629a9469a32e","order_by":2,"name":"Feifei Zhang","email":"","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Feifei","middleName":"","lastName":"Zhang","suffix":""},{"id":538954,"identity":"40ef31ca-a6ee-4bfd-9f20-5c54755b23ef","order_by":3,"name":"Zhanwei Wang","email":"","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhanwei","middleName":"","lastName":"Wang","suffix":""},{"id":538955,"identity":"f38f44a1-a746-42a4-a72a-2778f50fdb7f","order_by":4,"name":"Hongbin Chen","email":"","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hongbin","middleName":"","lastName":"Chen","suffix":""},{"id":538956,"identity":"fea1cf82-810a-4186-850a-9756688fe1f1","order_by":5,"name":"Xiaojuan Wang","email":"","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Xiaojuan","middleName":"","lastName":"Wang","suffix":""},{"id":538957,"identity":"66d13f41-15ed-42e9-96ea-dd28db1affad","order_by":6,"name":"Yawei Zhang","email":"","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yawei","middleName":"","lastName":"Zhang","suffix":""},{"id":538958,"identity":"97e2e4a0-5421-4c2a-9751-47d1edb5d69c","order_by":7,"name":"Shuguang Li","email":"","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Shuguang","middleName":"","lastName":"Li","suffix":""},{"id":538959,"identity":"c631f588-5215-4557-83b2-f694007547c1","order_by":8,"name":"Hui Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAp0lEQVRIiWNgGAWjYDACCQaGwww8Njz8/A2kaUmTkZxxgAQtzEBdNgYNCUTqMLjdY3i4QOY8jwHDAcYPH3OI0XLnjMHhGTy3ecyZG5glZ24jQovZjRyDwzxALZYNB9iYeUnQco7H4EACaVoOkKDF/kZaAdAvyTySMw42E+cXyRnJmz8X9tjZ8/M3H/zwkRgtYMDYAyYbiFUPAj9IUTwKRsEoGAUjDgAAPSE2aRb/dpEAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-9220-0357","institution":"Peking University People's Hospital","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2020-05-01 16:36:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-26430/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-26430/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12866-020-01870-z","type":"published","date":"2020-06-29T12:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":1049748,"identity":"e8b53da5-99f4-4a60-bb94-bab7d7463426","added_by":"auto","created_at":"2020-05-07 18:11:16","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":495433,"visible":true,"origin":"","legend":"Scatter plot of ceftazidime-avibactam Etest MICs versus BMD MICs against Enterobacterales. Dotted lines represent the susceptibility breakpoint for ceftazidime-avibactam. VMEs: very major errors (false susceptible); MEs: major errors (false resistant). The gray background indicates that the MIC of the Etest did not satisfy the essential agreement compared with the MIC of the BMD; the yellow background indicates that a major error occurred in the MIC result of the Etest compared with the MIC of the BMD.","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-26430/v1/Figure1.jpg"},{"id":1049749,"identity":"db049b48-852e-49f8-a0d2-7d1f54a30e9f","added_by":"auto","created_at":"2020-05-07 18:11:16","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":458489,"visible":true,"origin":"","legend":"Scatter plot of ceftazidime-avibactam Etest MICs versus BMD MICs against Pseudomonas aeruginosa. Dotted lines represent the susceptibility breakpoint for ceftazidime-avibactam. VMEs: very major errors (false susceptible); MEs: major errors (false resistant). The gray background indicates that the MIC of the Etest did not satisfy the essential agreement compared with the MIC of the BMD; the yellow background indicates that three major errors occurred in the MIC results of the Etest compared with the MIC of the BMD.","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-26430/v1/Figure2.jpg"},{"id":1049750,"identity":"ad958fbc-6947-4ca3-9404-3ae0784cf544","added_by":"auto","created_at":"2020-05-07 18:11:16","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":680675,"visible":true,"origin":"","legend":"Scatter plot of ceftazidime-avibactam zone diameters versus BMD MICs against Enterobacterales. Dotted lines represent the susceptibility breakpoint for ceftazidime-avibactam. VMEs: very major errors (false susceptible); MEs: major errors (false resistant). The yellow background indicates that a major error occurred when comparing the results of the disk diffusion method with the results of the BMD. The red background indicates that two very major errors occurred when comparing the results of the disk diffusion method with the results of the BMD.","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-26430/v1/Figure3.jpg"},{"id":1049751,"identity":"daf445da-f9fb-47df-bd76-349a0cd8b166","added_by":"auto","created_at":"2020-05-07 18:11:16","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":531243,"visible":true,"origin":"","legend":"Scatter plot of ceftazidime-avibactam zone diameters versus BMD MICs against Pseudomonas aeruginosa. Dotted lines represent the susceptibility breakpoint for ceftazidime-avibactam. VMEs: very major errors (false susceptible); MEs: major errors (false resistant). The yellow background indicates that four major errors occurred when comparing the results of the disk diffusion method with the results of the BMD. The red background indicates that a very major error occurred when comparing the results of the disk diffusion method with the results of the BMD.","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-26430/v1/Figure4.jpg"},{"id":15667035,"identity":"c669b79d-7049-41fb-bca4-36b9ba82b48e","added_by":"auto","created_at":"2021-11-18 13:39:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1146871,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-26430/v1/9e525257-fcde-4fbb-ab66-b362814f6691.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eEvaluation of Etests and the disk diffusion method for assessment of the activity of ceftazidime-avibactam against \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003ePseudomonas aeruginosa \u003c/em\u003ein China\u003c/p\u003e","fulltext":[{"header":"Background","content":" \u003cp\u003eGram-negative bacilli, particularly carbapenem-resistant \u003cem\u003eEnterobacterales\u003c/em\u003e (CRE) and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e, exhibit major antimicrobial resistance worldwide, including in European countries, the United States of America (USA), and China [1\u0026ndash;3]. The approval of ceftazidime-avibactam for clinical use in Europe and the USA has brought new treatment options to CRE-infected patients, particularly those with serine-carbapenemase resistance mechanisms [4, 5]. Ceftazidime-avibactam was approved for use in China in 2019. However, currently available commercial antimicrobial susceptibility test kits have not yet been developed for analysis of ceftazidime-avibactam resistance in China, and in patients with infections caused by CRE, which are resistant to multiple antimicrobials, the results of ceftazidime-avibactam susceptibility tests are urgently needed to facilitate appropriate targeted treatment. Although ceftazidime-avibactam has excellent in vitro activity against carbapenem-resistant \u003cem\u003eKlebsiella pneumoniae\u003c/em\u003e (CRKP) and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e strains, a small number of resistant strains will still appear during treatment [6\u0026ndash;8]. Therefore, susceptibility test results for ceftazidime-avibactam are even more critical.\u003c/p\u003e \u003cp\u003eIn most of the laboratories in China, performing the standard broth microdilution method (BMD) is challenging. Therefore, other rapid, simple methods are required as alternatives to determine ceftazidime-avibactam susceptibility. In this study, we evaluated two antimicrobial susceptibility test methods for ceftazidime-avibactam, i.e., the Etest method and the disk diffusion method with the standard BMD, to evaluate whether these easy-to-use methods could replace standard methods when required in the clinical setting.\u003c/p\u003e "},{"header":"Materials And Methods","content":" \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eGroups\u003c/h2\u003e \u003cp\u003eIsolates were divided into two groups, i.e., the random selection group and the stock group. For the random selection group, we randomly selected 140 \u003cem\u003eEnterobacterales\u003c/em\u003e and 46 \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e strains from clinical nonrepeated isolates obtained at Peking University People\u0026rsquo;s Hospital. Among these samples, 59.3% (83/140) of \u003cem\u003eEnterobacterales\u003c/em\u003e and 56.5% (26/46) of \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e strains were defined as fresh strains from clinical isolates obtained within 1 month prior to testing (November 2019 to March 2020). The remaining strains in the random selection group were obtained from the strain repository of Peking University People\u0026rsquo;s Hospital from January 2018 to October 2019. The 140 strains of \u003cem\u003eEnterobacterales\u003c/em\u003e used in the testing included 13 species, i.e., 25\u0026nbsp;\u003cem\u003eK. pneumoniae\u003c/em\u003e, 19 \u003cem\u003eEscherichia coli\u003c/em\u003e, 18 \u003cem\u003eProteus mirabilis\u003c/em\u003e, 17 \u003cem\u003eEnterobacter cloacae\u003c/em\u003e, 16 \u003cem\u003eSerratia marcescens\u003c/em\u003e, 15 \u003cem\u003eCitrobacter freundii\u003c/em\u003e, 14\u0026nbsp;\u003cem\u003eK. oxytoca\u003c/em\u003e, four \u003cem\u003eProteus vulgaris\u003c/em\u003e, three \u003cem\u003eMorganella morganii\u003c/em\u003e, three \u003cem\u003eProvidencia stuartii\u003c/em\u003e, two \u003cem\u003eProvidencia rettgeri\u003c/em\u003e, two \u003cem\u003eK. aerogenes\u003c/em\u003e, and two \u003cem\u003eCitrobacter koseri\u003c/em\u003e strains. For the stock group, we selected 54 strains of \u003cem\u003eEnterobacterales\u003c/em\u003e from 15 hospitals in the CRE China-Network from January 2015 to October 2019 and requested that the minimum inhibitory concentration (MIC) of ceftazidime-avibactam be between 2 and 256\u0026nbsp;\u0026micro;g/mL. Among these strains, six strains (11.1%) showed MICs for ceftazidime-avibactam of between 8 and 16\u0026nbsp;\u0026micro;g/mL, and 15 strains (27.8%) showed MIC between 4 and 32\u0026nbsp;\u0026micro;g/mL. The carbapenem-resistance genes present in these strains were elucidated in previous studies [9]. The 54 strains of \u003cem\u003eEnterobacterales\u003c/em\u003e used in this study included 29\u0026nbsp;\u003cem\u003eK. pneumoniae\u003c/em\u003e (18 strains having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eKPC\u003c/sub\u003e gene and 10 strains having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eNDM\u003c/sub\u003e gene), 12 \u003cem\u003eEscherichia coli\u003c/em\u003e (two strains having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eKPC\u003c/sub\u003e gene and seven strains having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eNDM\u003c/sub\u003e gene), eight \u003cem\u003eEnterobacter cloacae\u003c/em\u003e (one strain having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eKPC\u003c/sub\u003e gene, five strains having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eNDM\u003c/sub\u003e gene, one strain having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eIMP\u003c/sub\u003e gene, and one strain having \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eVIM\u003c/sub\u003e gene), three \u003cem\u003eK. oxytocai\u003c/em\u003e (two strains having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eIMP\u003c/sub\u003e gene and one strain having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eNDM\u003c/sub\u003e gene), and two \u003cem\u003eCitrobacter freundii\u003c/em\u003e (one strain having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eIMP\u003c/sub\u003e gene and one strain having the \u003cem\u003ebla\u003c/em\u003e\u003csub\u003eNDM\u003c/sub\u003e gene).\u003c/p\u003e \u003cp\u003eWe selected 31 strains of \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e from the eight hospitals involved in the CARES 2018 project as stock group strains and required the MIC of ceftazidime-avibactam to be between 2 and 256\u0026nbsp;\u0026micro;g/mL. Among these strains, 12 strains (38.7%) had MICs for ceftazidime-avibactam between 8 and 16\u0026nbsp;\u0026micro;g/mL, and 25 strains (80.6%) had MICs between 4 and 32\u0026nbsp;\u0026micro;g/mL.\u003c/p\u003e \u003cp\u003eAll strains were removed from a -80\u0026nbsp;\u0026deg;C ultra-low temperature refrigerator and transferred to Columbia blood agar twice before antimicrobial susceptibility testing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eAntimicrobial susceptibility testing\u003c/h2\u003e \u003cp\u003eFor the disk diffusion method, ceftazidime-avibactam disks were obtained from Oxoid (Thermo Scientific, China) The content of ceftazidime-avibactam in each disk was 30\u0026nbsp;\u0026micro;g/20\u0026nbsp;\u0026micro;g. The operation process was strictly tested following the requirements of the CLSI standardized method [10].\u003c/p\u003e \u003cp\u003eFor the Etest gradient diffusion method, ceftazidime-avibactam Etest strips were obtained from BioM\u0026eacute;rieux (Marcy l\u0026rsquo;Etoile, France). The test was performed in strict accordance with the manufacturer\u0026rsquo;s instructions. The ceftazidime-avibactam concentration gradient ranged from 0.016 to 256\u0026nbsp;\u0026micro;g/mL. When the Etest MIC value was between the standard value and twice the standard value (0.016, 0.032, 0.064, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128, and 256), the high standard value will be read as the MIC.\u003c/p\u003e \u003cp\u003eThe MH agar used for both the disk diffusion method and the Etest gradient diffusion method for antimicrobial susceptibility testing was obtained from Oxoid (Thermo Scientific Inc).\u003c/p\u003e \u003cp\u003eThe BMD was performed strictly following CLSI guidelines [11]. Ceftazidime and avibactam powers were obtained from Pfizer (USA). The concentration ranged from the standard double dilution of 0.016\u0026nbsp;\u0026micro;g/mL to 256\u0026nbsp;\u0026micro;g/mL.\u003c/p\u003e \u003cp\u003eQuality control and colony counting are performed simultaneously for each batch of experiments. \u003cem\u003eEscherichia coli\u003c/em\u003e ATCC 25922, \u003cem\u003eK. pneumoniae\u003c/em\u003e ATCC 700603, \u003cem\u003eEscherichia coli\u003c/em\u003e ATCC 35218, and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e ATCC 27853 were used as experimental quality control strains. The experiment was considered valid only when the experimental values of all the quality control strains were within the acceptable range.\u003c/p\u003e \u003cp\u003eThe MICs and zone diameters of ceftazidime-avibactam for \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e were interpreted according to CLSI M100 30th edition [11]. Briefly, MICs of less than or equal to 8/4\u0026nbsp;\u0026micro;g/mL or a zone diameter of greater than or equal to 21\u0026nbsp;mm indicated that the strain was susceptible, whereas MICs of greater than or equal to 16/4\u0026nbsp;\u0026micro;g/mL or a zone diameter of less than or equal to 20\u0026nbsp;mm indicated that the strain was resistant.\u003c/p\u003e \u003cp\u003eEssential agreement (EA) indicated that the difference between the MIC value measured by Etest and the BMD did not exceed one dilution factor. Categorical agreement (CA) indicated that the BMD method was consistent with the classification results from the disk diffusion method and Etest method based on the same CLSI breakpoints.\u003c/p\u003e \u003cp\u003eVery major errors (VMEs) indicated that the strain was susceptible by Etest or the disk diffusion method but resistant by the BMD. Major errors (MEs) indicated that the strain was susceptible by the BMD but resistant by Etest or the disk diffusion method.\u003c/p\u003e \u003c/div\u003e "},{"header":"Result","content":" \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eEtest versus the BMD\u003c/h2\u003e \u003cp\u003eFor 194 \u003cem\u003eEnterobacterales\u003c/em\u003e strains, no VMEs were found using the Etest method. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the overall CA rate was 99.5%, and the overall EA rate was 95.9%. The CA rate of the stock group was 90.7%, and the CA rate in the random selection group was 97.9%. When comparing Etest results with BMD results, we found that the MICs of eight strains exceeded the two dilution factors. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the Etest MICs of 102 (52.5%) strains were consistent with the BMD MICs. The Etest MICs of 71 (36.6%) strains were a dilution multiple higher than the BMD MICs. Only 12 (6.2%) strains had Etest MICs that were a dilution multiple lower than the BMD MICs.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEvaluation of essential and categorical agreement between the BMD method and Etests or the disk diffusion method for analysis of ceftazidime-avibactam antimicrobial susceptibility\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"13\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eOrganisms\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNo. of strains tested\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c8\" namest=\"c3\"\u003e \u003cp\u003eEtest\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c13\" namest=\"c10\"\u003e \u003cp\u003eDisk diffusion\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eNo. of EA\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eEA%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eNo. of CA\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eCA%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eNo. of VMEs\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eNo. of MEs\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003eNo. of CA\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003eCA%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u003cb\u003eNo. of VMEs\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cb\u003eNo. of MEs\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan type=\"BoldItalic\" class=\"BoldItalic\" name=\"Emphasis\"\u003eEnterobacterales\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRandom selection Group\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e140\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e137\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e97.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e140\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e140\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStock group:\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e90.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e98.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e94.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal in \u003cem\u003eEnterobacterales\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e194\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e186\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e95.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e193\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e99.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e191\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e98.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan type=\"BoldItalic\" class=\"BoldItalic\" name=\"Emphasis\"\u003ePseudomonas aeruginosa\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRandom selection Group\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e97.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e93.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStock group:\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e90.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e90.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e93.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal in \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e94.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e96.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e93.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal in all tested strains\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e271\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e259\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e95.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e267\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e98.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e263\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e97.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"13\"\u003eEA: essential agreement; CA: categorical agreement; VMEs: very major errors (false susceptible); MEs: major errors (false resistant)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFor 77 \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e strains, no VMEs were found using the Etest method. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the overall CA rate was 96.1%, and the overall EA rate was 94.8%. The CA rate in the stock group was 90.3%, and the CA rate in the random selection group was 100%. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the Etest MICs of 45 (58.4%) strains were consistent with the MICs obtained by the BMD. The Etest MICs of 22 (28.6%) strains were one dilution higher than those obtained by the BMD, whereas those of six (7.8%) strains were one dilution lower than the MICs obtained by the BMD. For one strain, the Etest MIC was two dilutions higher than those obtained by the BMD. Three MEs appeared in the stock group when the Etest method was used.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eDisk diffusion method versus BMD\u003c/h2\u003e \u003cp\u003eA comparison of the disk diffusion method and BMD results for 194 \u003cem\u003eEnterobacterales\u003c/em\u003e strains (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) showed that there were no linear relationships between zone diameter and MIC. The overall CA rate in the 194 \u003cem\u003eEnterobacterales\u003c/em\u003e strains was 98.5%. Two VMEs and one ME were found using the disk diffusion method in the stock group; all were for \u003cem\u003eK. pneumoniae\u003c/em\u003e strains. No VMEs or MEs were found using the disk diffusion method in the random selection group. There were 22 strains of \u003cem\u003eEnterobacterales\u003c/em\u003e with zone diameters of 2\u0026nbsp;mm (19\u0026ndash;22\u0026nbsp;mm susceptibity breakpoint). Forty-one of the 45 resistant strains obtained by BMD had zone diameters in the range of 13\u0026ndash;20\u0026nbsp;mm.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn a comparison of the results of the disk diffusion method and BMD for 77 \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e strains, the number of MEs was four, and the number of VMEs was 1. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the overall CA rate was 93.5%. Moreover, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, when the zone diameter was 20\u0026nbsp;mm, the MICs obtained by the BMD method were 4, 8, 16, or 64\u0026nbsp;\u0026micro;g/mL.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e "},{"header":"Discussion","content":" \u003cp\u003eIn the past ten years, the incidence of CRE, particularly CRKP, has increased significantly in China. The latest China Antimicrobial Resistance Surveillance System (CARSS) data show that the incidence of CRKP nationwide is as high as 10.1% (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.carss.cn/Report/Details?aId=648\u003c/span\u003e\u003c/span\u003e). However, few active antibacterial agents, such as tigecycline and colistin, are available to treat CRKP in the clinical setting [12, 13], resulting in high mortality worldwide. Previous molecular epidemiological data show that more than 70% of CRE isolated in China from 2012 to 2016 produce KPC-type carbapenemases [9]. Ceftazidime-avibactam, a drug with potent antibacterial activity against serine-carbapenemase, was approved for use in China in 2019. Recent retrospective studies have shown that ceftazidime-avibactam treatment of CRKP and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e infection in patients who have undergone solid organ transplantation improves clinical success rates [14, 15]. Despite these promising findings, ceftazidime-avibactam antimicrobial susceptibility test results are essential for clinical use of this treatment. However, no ceftazidime-avibactam combination kits are available for assessing resistance in China.\u003c/p\u003e \u003cp\u003eTo the best of our knowledge, this is the first study comparing Etests, the disk diffusion method, and the BMD with regard to detection of ceftazidime-avibactam susceptibility in China. Compared with the standard BMD method, no VMEs were found using the Etest method. The results of Etest MICs and BMD MICs were reasonably well correlated for both \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e. The overall of EA% of 271 tested strains was 95.6%. Compared with the BMD method, the Etest method exhibited an excellent linear correlation, supporting the use of this approach as an alternative to the standard clinical method without considering economic costs. This result was similar to the previous research findings of other authors [16]. The disk diffusion method is easy to implement in the clinical setting from an economic standpoint. The CA% values of the ceftazidime-avibactam disk diffusion method against \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e were 98.5% and 93.5%, respectively, similar to the findings of Shields and other scholars [16, 17]. Indeed, our results showed that application of the disk diffusion method was more appropriate for \u003cem\u003eEnterobacterales\u003c/em\u003e than for \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e. Notably, however, the disk diffusion method did not have an excellent linear correlation with BMD. Therefore, the zone diameters of strains near the breakpoints (\u0026plusmn;\u0026thinsp;2\u0026nbsp;mm) should be checked by the BMD carefully, consistent with other research results [17, 18]. This should also be considered when users refer to the new version of CLSI M100, which suggests using the disk diffusion method [11].\u003c/p\u003e "},{"header":"Conclusions","content":"\u003cp\u003eIn conclusion, for \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e, Etests and the disk diffusion method showed good performance as alternative methods to meet the needs of clinical treatment interpretation. The application of the disk diffusion method was superior for \u003cem\u003eEnterobacterales\u003c/em\u003e compared with \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e The authors declare that they have no competing interests\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e This work was supported by National Natural Science Foundation of China (81625014)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions:\u003c/strong\u003e HW conceived and designed the study. QW, FZ, HC, XW, YZ and SL performed experiments described in this study. QW wrote the draft, and HW revised it. All authors approved the final version.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests:\u003c/strong\u003e The authors declare no conflicts of interest in this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements: \u003c/strong\u003eWe would like to thank Editage (www.editage.cn) for English language editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eChinese XDRCWG, Guan X, He L, Hu B, Hu J, Huang X, Lai G, Li Y, Liu Y, Ni Y\u003cem\u003e et al\u003c/em\u003e: \u003cstrong\u003eLaboratory diagnosis, clinical management and infection control of the infections caused by extensively drug-resistant Gram-negative bacilli: a Chinese consensus statement\u003c/strong\u003e. \u003cem\u003eClinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases \u003c/em\u003e2016, \u003cstrong\u003e22 Suppl 1\u003c/strong\u003e:S15-25.\u003c/li\u003e\n\u003cli\u003eHu F, Zhu D, Wang F, Wang M: \u003cstrong\u003eCurrent Status and Trends of Antibacterial Resistance in China\u003c/strong\u003e. \u003cem\u003eClinical infectious diseases : an official publication of the Infectious Diseases Society of America \u003c/em\u003e2018, \u003cstrong\u003e67\u003c/strong\u003e(suppl_2):S128-S134.\u003c/li\u003e\n\u003cli\u003eGrundmann H, Glasner C, Albiger B, Aanensen DM, Tomlinson CT, Andrasević AT, Cant\u0026oacute;n R, Carmeli Y, Friedrich AW, Giske CG\u003cem\u003e et al\u003c/em\u003e: \u003cstrong\u003eOccurrence of carbapenemase-producing Klebsiella pneumoniae and Escherichia coli in the European survey of carbapenemase-producing Enterobacteriaceae (EuSCAPE): a prospective, multinational study\u003c/strong\u003e. \u003cem\u003eThe Lancet Infectious Diseases \u003c/em\u003e2017, \u003cstrong\u003e17\u003c/strong\u003e(2):153-163.\u003c/li\u003e\n\u003cli\u003ePogue JM, Bonomo RA, Kaye KS: \u003cstrong\u003eCeftazidime/Avibactam, Meropenem/Vaborbactam, or Both? 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Ceftazidime-avibactam was approved for use in China in 2019. However, currently available commercial antimicrobial susceptibility test kits have not yet been developed. Here, we evaluated the Etest and disk diffusion method for assessment of the efficacy of ceftazidime-avibactam against \u003cem\u003eEnterobacterales\u003c/em\u003e and\u003cem\u003e P. aeruginosa \u003c/em\u003ein China. \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e In total, 194 \u003cem\u003eEnterobacterales\u003c/em\u003e and 77 \u003cem\u003eP. aeruginosa \u003c/em\u003eisolates,\u003cem\u003e \u003c/em\u003ewhich were divided into a random selection group (140\u003cem\u003e Enterobacterales \u003c/em\u003eand 54 \u003cem\u003eP. aeruginosa \u003c/em\u003eisolates) and a stock group (46\u003cem\u003e Enterobacterales \u003c/em\u003eand 31 \u003cem\u003eP. aeruginosa \u003c/em\u003eisolates), were assessed by the Etest, disk diffusion, and broth microdilution (BMD) methods. Minimum inhibitory concentrations (MICs) and zone diameters were interpreted according to the CLSI M100 30\u003csup\u003eth\u003c/sup\u003e edition. For all 271 \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003eP. aeruginosa \u003c/em\u003eisolates, no very major errors were found using Etests. The overall categorical agreement rates (CA%) of Etests for \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003eP. aeruginosa\u003c/em\u003e were 99.5% (193/194) and 96.1% (74/77), respectively. The overall essential agreement rates (EA%) of Etests for \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003eP. aeruginosa\u003c/em\u003e were 95.9% (186/194) and 94.8% (73/77), respectively. In both the random selection and stock groups, EA% and CA% values of Etests exceeded 90%. Overall CA% values of the disk diffusion method for \u003cem\u003eEnterobacterales\u003c/em\u003e and\u003cem\u003e P. aeruginosa\u003c/em\u003e were 98.5% (191/194) and 93.5% (71/77), respectively. There was no linear relationship between zone diameter and BMD MIC. \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConclusions: \u003c/strong\u003eFor \u003cem\u003eEnterobacterales\u003c/em\u003e and \u003cem\u003eP. aeruginosa\u003c/em\u003e, Etests and the disk diffusion method could have better performance as alternative methods to meet the needs of clinical treatment interpretation. Application of the disk diffusion method in \u003cem\u003eEnterobacterales\u003c/em\u003e was superior to that in \u003cem\u003eP. aeruginosa\u003c/em\u003e.\u003c/p\u003e","manuscriptTitle":"Evaluation of Etests and the disk diffusion method for assessment of the activity of ceftazidime-avibactam against Enterobacterales and Pseudomonas aeruginosa in China","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2020-05-07 18:11:15","doi":"10.21203/rs.3.rs-26430/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorAssigned","content":"","date":"2020-05-01T12:00:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"","date":"2020-04-30T12:00:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2020-04-30T12:00:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2020-04-30T12:00:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-microbiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mcro","sideBox":"Learn more about [BMC Microbiology](http://bmcmicrobiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/mcro","title":"BMC Microbiology","twitterHandle":"#bmcmicrobiology","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9133a2e6-0f05-45c7-b564-06303357ec2a","owner":[],"postedDate":"May 7th, 2020","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":95485,"name":"Applied \u0026 Industrial Microbiology"},{"id":95486,"name":"General Microbiology"}],"tags":[],"updatedAt":"2020-07-05T15:01:15+00:00","versionOfRecord":{"articleIdentity":"rs-26430","link":"https://doi.org/10.1186/s12866-020-01870-z","journal":{"identity":"bmc-microbiology","isVorOnly":false,"title":"BMC Microbiology"},"publishedOn":"2020-06-29 12:00:00","publishedOnDateReadable":"June 29th, 2020"},"versionCreatedAt":"2020-05-07 18:11:15","video":"","vorDoi":"10.1186/s12866-020-01870-z","vorDoiUrl":"https://doi.org/10.1186/s12866-020-01870-z","workflowStages":[]},"version":"v1","identity":"rs-26430","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-26430","identity":"rs-26430","version":["v1"]},"buildId":"FbvkV6FR0MCFSLy54lSbu","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}