Bacteremia in Horses Undergoing Routine Dental Prophylaxis: Before, During, and After the Procedure

Bacteremia in Horses Undergoing Routine Dental Prophylaxis: Before, During, and After the Procedure | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 16 December 2025 V1 Latest version Share on Bacteremia in Horses Undergoing Routine Dental Prophylaxis: Before, During, and After the Procedure Authors : Allison Dockery 0009-0000-5181-3413 [email protected] , Canaan Whitfield-Cargile 0000-0002-9743-8783 , Vanessa Knopp , and Taylor Sinay Authors Info & Affiliations https://doi.org/10.22541/au.176590451.16286583/v1 169 views 95 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Background: Transient bacteremia after dental procedures is well-documented in both human and veterinary literature, but the prevalence and clinical significance in horses remains largely unexplored. Objectives: This study aims to assess whether routine dental prophylaxis in clinically normal horses causes bacteremia, using culture and 16S rDNA sequencing. Our central hypothesis is that a percentage of horses will develop transient venous bacteremia in the immediate post-procedural period following dental prophylaxis. Study design: Prospective, observational study Materials and Methods: Venous blood samples from 20 clinically normal horses without evidence of significant dental disease were collected before, immediately after, 30 minutes, 60 minutes, and 24 hours post-procedure and submitted for routine aerobic and anaerobic bacterial culture and 16S rDNA sequencing. Results: Data were analyzed for normality by Shapiro-Wilk and Kruskal–Wallis analysis of variance (ANOVA) on ranks was performed on non-normally distributed data. 16 of 20 horses had positive blood cultures at one or more time points with no significant difference in the proportion of positive blood cultures among time points but differential abundance analysis identified 8 bacterial families with increased and 3 with decreased relative abundance at one or more post-procedural time points compared to baseline. Several of these families have been associated with the equine oral or gastrointestinal microbiota, whereas others are commonly reported in plant soil and reagent-associated communities. Main limitations: Small sample size, lack of age-matched controls, absence of technical negative controls, and the low-biomass nature of blood samples limit interpretation. Conclusions: Culturable bacteria and bacterial DNA were isolated from blood samples collected from horses undergoing routine dental prophylaxis, though overall culture positivity and community diversity remained stable. Despite lacking technical negative controls, differential abundance results indicate mild, transient post-procedure changes consistent with transient, low-level bacteremia. Potential influence of environmental or reagent contamination, however, warrants cautious interpretation. Bacteremia in Horses Undergoing Routine Dental Prophylaxis: Before, During, and After the Procedure Running title: Bacteremia risk with routine dental Keywords: horse; dental; bacteremia; blood culture; NextGeneration sequencing Summary Background: Transient bacteremia after dental procedures is well-documented in both human and veterinary literature, but the prevalence and clinical significance in horses remains largely unexplored. Objectives: This study aims to assess whether routine dental prophylaxis in clinically normal horses causes bacteremia, using culture and 16S rDNA sequencing. Our central hypothesis is that a percentage of horses will develop transient venous bacteremia in the immediate post-procedural period following dental prophylaxis. Study design: Prospective, observational study Materials and Methods: Venous blood samples from 20 clinically normal horses without evidence of significant dental disease were collected before, immediately after, 30 minutes, 60 minutes, and 24 hours post-procedure and submitted for routine aerobic and anaerobic bacterial culture and 16S rDNA sequencing. Results: Data were analyzed for normality by Shapiro-Wilk and Kruskal–Wallis analysis of variance (ANOVA) on ranks was performed on non-normally distributed data. 16 of 20 horses had positive blood cultures at one or more time points with no significant difference in the proportion of positive blood cultures among time points but differential abundance analysis identified 8 bacterial families with increased and 3 with decreased relative abundance at one or more post-procedural time points compared to baseline. Several of these families have been associated with the equine oral or gastrointestinal microbiota, whereas others are commonly reported in plant soil and reagent-associated communities. Main limitations: Small sample size, lack of age-matched controls, absence of technical negative controls, and the low-biomass nature of blood samples limit interpretation. Conclusions: Culturable bacteria and bacterial DNA were isolated from blood samples collected from horses undergoing routine dental prophylaxis, though overall culture positivity and community diversity remained stable. Despite lacking technical negative controls, differential abundance results indicate mild, transient post-procedure changes consistent with transient, low-level bacteremia. Potential influence of environmental or reagent contamination, however, warrants cautious interpretation. Clinical Relevance • This study provides preliminary data on the presence of bacterial DNA and occasional positive blood cultures in horses undergoing routine dental prophylaxis. • Clinical implications remain unclear, and no changes to current dental recommendations or routine antibiotic use in healthy horses are indicated. • These preliminary results may help guide the design of future, more controlled investigations into transient bacteremia and potential risk factors in equine dentistry. Introduction The equine oral microbiome includes a variety of bacteria such as Actinobacillus , Fusobacterium , Leptotrichia , Porphyromonas , Prevotella , Streptococcus , and Veillonella (Townsend et al. 2021). Healthy horses have been noted to have a predominance of Gram-positive cocci like Streptococcus , with Actinobacillus , Gemella , Corynebacterium and Moraxella frequently reported (Townsend et al. 2021; Kennedy et al. 2016). In healthy horses, subgingival samples have identified Gammaproteobacteria , Firmicutes , and Bacteroidetes as well as Actinobacillus and Pasteurellaceae species as part of the oral microbiome (Gao et al. 2016). In contrast, Tannerella and Treponema species become more prominent in horses with periodontal disease (Sykora et al. 2013; Kennedy et al. 2016). Acid-producing bacteria like Streptococcus contribute to peripheral caries (Borkent et al., 2019), while the red complex bacteria, including Porphyromonas gingivalis , Treponema denticola , and Tannerella forsythia , are involved in more significant periodontal disease and have been associated with equine odontoclastic tooth hypercementosis (EOTRH) (Sykora et al. 2014). Transient bacteremia related to dental procedures is a well-documented phenomenon in both human and veterinary medicine. (Nieves et al. 1997; Blazevich and Miles 2024; Kern et al. 2016). Numerous studies have demonstrated a connection between routine dental prophylaxis and oral surgeries, often identifying within five to 40 minutes the same bacteria in blood cultures, with several studies showing similar isolates to gingival cultures (Martins et al. 2022; Nieves et al. 1997; Kern et al. 2016, Townsend et al. 2021). Kern et al. (2016) found that 90% of the 20 adult horses in their study had positive blood cultures at least once before, during, or after exodontia, indicating the presence of bacteremia at various stages. Other studies, however, have demonstrated bacteremia with no difference noted between dentistry and non-dentistry groups alluding to perhaps a more complex and transient blood microbiome (Harari et al. 1993). This is supported by the functional use of teeth during activities such as chewing resulting in the translocation of oral bacteria into the bloodstream (Sreenivasan et al., 2017). The isolated pathogenic bacteria from the equine oral cavity being similar to other species, and including Streptococcus. , Bacillus , Actinobacillus , Fusobacterium. , and Prevotella species (Kern et al. 2017). While research on oral microbiota especially regarding pathologic conditions such as periodontal disease, diastemas, and caries has been reported, limited research on bacteremia has been performed with the few publications focusing on extractions of diseased teeth and only one report investigating routine dentistry in donkeys. (Kennedy et al. 2016; Gao et al. 2016; Borkent et al. 2020; Zhu et al. 2020) The consequences of transient bacteremia in horses are not yet fully understood; however, severe infectious complications, such as endocarditis, meningitis, and pneumonia, have been documented in various species (Verdegaal et al. 2010; Ardnt et al. 2010; Zetterström et al. 2021; Glickman et al. 2009; Paju et al. 2007). While reports of these complications in horses are infrequent, they raise important concerns, especially when dental procedures coincide with other invasive interventions like intra-articular steroid injections or surgical procedures. Recent literature indicates that even low levels of bacteremia may significantly contribute to the development of infectious complications in human medicine therefore dental care in conjunction of antibiotics is recommended in compromised individuals prior to initiating treatments such as immunosuppressive therapies (Juras et al. 2024). The risk of bacteremia is particularly relevant in the context of periodontal disease, where a significant association has been observed between the severity of dental conditions and cardiovascular issues, such as endocarditis (Glickman et al., 2009). Despite advancements in equine dentistry over the past two decades, periodontal disease affects an estimated 13% to 75% of horses, particularly as they age (Occhiogrosso et al 2023; Rodrigues et al. 2013; Nuttall and Ravenhill 2019). This study aims to investigate the incidence of bacteremia associated with routine odontoplasty (floating) in clinically normal horses, hypothesizing that the procedures may result in transient bacteremia. Identification of bacteria through culturing and molecular techniques will improve understanding of dental pathology and potential risks associated with equine dentistry to guide future recommendations, ultimately informing best practices in veterinary medicine. Materials and Methods Animals The study group consisted of 20 apparently clinically healthy adult horses. All horses used in the study were from the XXX’s teaching herd and presented for annual routine dental prophylaxis but otherwise showed no evidence of significant dental disease (nasal discharge, weight loss, quidding, or choke). A brief physical examination was performed before each blood collection time point to confirm continued clinical normality. Horses used in this study were not administered any antimicrobial drugs within at least the 7 days prior to their dental procedure and no additional procedures were performed the day of their dental procedure. After dental prophylaxis, horses were withheld from feed until sedation had fully worn off. Sedation and blood sampling: The skin at the site of the venipuncture was clipped and prepared using 4% chlorhexidine and rinsed with 70% isopropanol prior to each blood sample. Immediately following skin disinfection, a blood sample (50ml) was collected from the jugular vein using a needle and syringe and immediately transferred to blood culture bottles and tubes containing ethylenediaminetetraacetic acid (EDTA). Blood samples were collected from each horse immediately before (T0) and immediately after (T1) the start of the procedure, as well as 30 minutes (T30), 60 minutes (T60), and 24 hours (T24) post-procedure. Each blood sample consisted of 20 mL of blood used to immediately inoculate two 10 mL blood culture bottles, one aerobic and one anaerobic, at each sample time. Before the blood was transferred, the syringe needle was exchanged for a new sterile needle, the plastic protective cap was removed from the blood culture bottle, and the rubber septum was disinfected with a sterile swab soaked in 70% isopropanol. Remaining blood was transferred into two tubes containing ethylenediaminetetraacetic acid (EDTA), placed on ice, and transported to the laboratory for storage at -20 C before being sent to a commercial facility for DNA isolation and sequencing. Microbiological processing Blood culture: The blood culture bottles were incubated at room temperature until submitted same day as last collection to the {masked for review} where the samples were then processed in a routine manner consistent with clinical samples. Blood microbiome: DNA was isolated from blood samples by a commercial facility (MRDNA Shallowater, TX) following standard protocols. The V4 region of the 16S rRNA gene was amplified and sequenced using paired-end Illumina sequencing. Sequencing data was then processed in house as previously described (Whitfield Cargile et al. 2024). Briefly, raw paired-end 16S rRNA sequences were processed using QIIME2 (v2024.10). Primers were trimmed, and quality filtering, denoising, and chimera removal were conducted with DADA2. Taxonomy was constructed using MAFFT and FastTree. These outputs were then exported for downstream analysis. Statistical analysis Sequencing data: Data were imported into R (v4.2.2) and analyzed using Phyloseq, ggplot2, and DESeq2. Alpha diversity (Shannon, Observed richness) and beta diversity (weighted and unweighted UniFrac PCoA) were calculated. Taxonomic composition was visualized with stacked bar plots, and differential abundance was assessed using DESeq2 with FDR-adjusted p-values (≤ 0.05). All analyses were performed with QIIME2 on the UGA high-performance computing cluster, and R analyses were conducted locally. Scripts are available upon request. Raw sequencing data has been archived in the National Center for Biotechnology Information (NCBI) Sequence Read Archice (SRA) Bioproject #PRJNAXXXX (Blinded for submission). Blood culture data: Blood culture results were classified as positive when any growth of bacteria was observed and negative when no growth was observed. Results were compared at each timepoint to baseline (t0) using a McNemar‘s test on SAS. Bacterial Culture Positive blood cultures were identified in 16 of 20 horses at one or more time points. Eight horses were positive at baseline (T0), with 3 to 8 horses testing positive at subsequent time points. Two horses were consistently positive across all sampling points, while two horse remained negative throughout the study (Table 1). Overall, only 47% of bacterial isolates were identified beyond Gram stain classification, and 53% were speciated using matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF). The identified bacteria were diverse, with several horses showing shifts in cultured organisms over time, including changes in Gram status and species identity. The most commonly isolated bacteria were Gram-positive bacilli, particularly Bacillus spp. (including B. altitudinis/pumilis and B. cereus ), followed by Gram-positive cocci such as Staphylococcus xylosus , and a smaller number of Gram-negative bacilli including Enterococcus casseliflavus and Acinetobacter lwoffii . Low numbers and variability however made identifying a distinct pattern difficult (Table 2). There was no significant difference in any of the time points when compared to baseline (T0 vs T1 p=0.0956; T0 vs T2 p= 0.7055; T0 vs T3 p=0.2568; T0 vs T4 p=0.4795). Sequencing Results The sequencing data from baseline samples (T0) were examined to determine whether bacterial DNA could be detected in healthy horses prior to dental prophylaxis. Bacterial DNA was detected in the blood of all horses, although it was not possible to distinguish endogenous bacterial material from environmental or reagent contamination in these low-biomass samples. Members of the phylum Pseudomonadota were overrepresented, with Actinomycetota, Bacillota , and Bacteroidota contributing to a lesser extent (Figure 1A). There was substantial variation among samples (Figure 1B). Only the phylum Pseudomonadota , specifically bacteria belonging to the family Xanthomonadaceae, was present accross all samples. Sequencing Results Microbiome Following Dental Prophylaxis Principal coordinates analysis (weighted UniFrac) demonstrated no clustering of samples by time point, with samples from all time points intermingled and no visible separation or shift in overall community structure following dental prophylaxis (Figure 2A). Measures of alpha diversity, including the Shannon index and observed features, were also similar across time points, with no statistically significant differences between baseline and any post-procedure sampling point (Figure 2B). Together, these results indicate that the detectable bacterial DNA profile in blood showed no global or diversity level changes after dental prophylaxis. Differential abundance analysis, however, identified a small number of bacterial families with statistically significant changes at one or more post-procedure time points including increases in in Peptoniphilaceae, Lachnospiraceae, Bacteroidaceae, Enterobacteriaceae, Nocardioidaceae, Paenibacillaceae, and Sphingobacteriaceae, and decreases in Weeksellaceae and Xanthobacteraceae (Figure 3). These shifts were temporally inconsistent and varied across horses, with no family exhibiting a uniform pattern over time. In addition, many of the families identified as differentially abundant are recognized environmental or reagent-associated taxa in low -biomass 16S datasets, and in the absence of technical negative controls these findings may reflect background contamination rather than true biological change. Discussion Bacteria are well-known causes of disease across species, including horses, yet our understanding of their role in equine periodontitis, dental disease and bacteremia remains poorly understood. Research on the equine oral microbiome is limited, and largely focused on pathological conditions, such as periodontal disease, diastemata, caries, and tooth extractions (Kennedy 2016, Gao 2016, Borkent 2020, Townsend et al. 2021). Previous studies have described the effects of dental disease and procedures in horses on bacteremia and microbiome changes. Townsend et al. (2021) showed that the 16S rRNA signatures of bacteria present at the gingiva, near an extracted diseased tooth, were similar to those detected in the bloodstream following exodontia, with bacteremia persisting for at least one-hour post-procedure. Examination of blood from healthy individuals in other species, including humans, dogs, cats, and cattle, discuss the presence of resident bacterial populations (Wittle et al., 2018; Scarcella et al., 2020; Scarcella et al., 2021; Vientos-Plotts et al., 2017). A recent study by Simms et al. (2025) investigating the microbiome of blood in clinically healthy horses found a variable and diverse resident microbiota. Blood samples in that study contained several clinically relevant bacterial genera, with Corynebacterium , Moraxella , Neisseria , Staphylococcus , and Streptococcus present in all samples. The results from that study, together with our findings, establish a reference for the blood microbiome of clinically healthy horses and provide new insight into potential microbiome shifts that could serve as future biomarkers for clinical disease. Furthermore, our study supports their observation that horses maintained in a closed environment with a shared diet preserve microbial diversity. The equine blood associated microbiota has not been extensively studied, particularly in the context of blood culture and sequencing based analyses. In other species, blood culture-based identification methods of bacteria are typically found to be challenging, largely due to the antimicrobial properties of blood that inhibit bacterial growth. MALDI-TOF, a newer more sophisticated method of accurately identifying microbial culture isolates through predominately their ribosomal proteins, have at least improved identification. Recent advances in culture-independent methods, such as next-generation sequencing, use polymerase chain reaction to identify bacteria based on their 16S rRNA signature and have expanded our understanding of the blood microbiota by identifying organisms based on sequence differences. However, a key limitation of this approach is its inability to distinguishing DNA from living and dead bacteria. Early investigations of the equine oral microbiome using bacterial culturing methods have identified Gram-positive cocci—especially Streptococci, Micrococci, and starch-hydrolyzing bacteria—as dominant members in healthy horses (Borkent 2020; Lundström 2020). Other genera such as Gemella spp., Actinobacillus spp., Corynebacterium spp., Moraxella spp., Actinobascillus spp., and Pasteurellaceae spp. have additionally been associated with periodontal health (Kern et al. 2017; Borkent et al. 2020; Sykora et al. 2014). Equine periodontal disease is marked by a shift from a predominantly Gram-positive, aerobic oral microbiota to one dominated by Gram-negative, anaerobic pathogens, promoting inflammation and periodontal pocket formation (Klough 2005). This study is the first to investigate the equine blood microbiome in clinically healthy adult horses before and after routine dental prophylaxis using both bacterial culture and 16S rDNA sequencing. Blood cultures in this study yielded positive blood cultures in 16 of 20 horses at one or more timepoints, with no significant differences across time points, suggesting the presence of bacteremia at various stages. This may indicate that transient bacteremia is a naturally occurring phenomenon in horses, potentially resulting from intermittent translocation of environmental or gastrointestinal bacteria into the bloodstream. Our results support the presence of a consistent core microbiome endogenous to equine blood. While bacteria were identified through both methods, the study’s design limits the ability to confirm whether these findings represent transient changes in the microbiota, true clinical bacteremia, or contamination . However, the results suggest that the equine blood microbiome may, at least in part, arise from the transient and sporadic translocation of commensal microbes from other body sites into the bloodstream. While data supported a possible microbial shift, low numbers and bacterial variability in this study didn’t provide a conclusive pattern as such, the possibility of contamination cannot be excluded, particularly given the absence of negative controls and the lack of triplicate sampling. Culture-independent molecular methods, such as next-generation sequencing offer broader detection by amplifying bacterial 16S rRNA gene regions, allowing identification of diverse taxa regardless of viability. In this study, 16S rDNA sequencing consistently identified bacterial DNA in the blood samples with post-procedural shifts in abundance observed among families, including Peptoniphilaceae, Lachnospiraceae, Bacteroidaceae, and Enterobacteriaceae. While many of these taxa are recognized as common environmental contaminants in molecular workflows, these are present in the equine gastrointestinal microbiome with several having disease associations such as colic. While these findings may reflect transient, low-level bacteremia, the inability of 16s rRNA sequencing to differentiate between live bacteria, dead cells, or extracellular fragments, combined with the absence of negative controls and quantitative data, limits the ability to draw definitive conclusions about the clinical relevance or origin of the detected microbial DNA. Given the absence of significant differences in bacterial presence before and after the procedure, the clinical implications of these findings remain unclear. While transient bacteremia has been documented in other species, this study neither confirms nor rules out its occurrence in horses related to dental procedures. The sporadic nature of positive cultures and bacterial DNA detection could suggest that low-level, transient bacteremia occurs naturally and is unrelated to specific procedures. Furthermore, the identification of bacterial families known to be common contaminants further complicates this interpretation. Several limitations affect the interpretation of these findings. The absence of negative controls, such as blood culture bottles handled identically but without blood, or sequencing blanks, limits the ability to rule out contamination and impacts interpretation of these findings. The small sample size, lack of age-matched controls, and absence of concurrent oral cultures further restrict conclusions. Additionally, 16S rDNA sequencing cannot distinguish between DNA from viable bacteria and non-viable fragments, nor can it quantify bacterial load. Future studies should address these limitations by incorporating rigorous negative controls, including blank cultures and sequencing blanks. Expanding the sampling timeframe and cohort size, and controlling for health variables such as immune status, would also strengthen future research. Including quantitative bacterial counts and concurrent oral sampling could provide more context to the findings. Further studies might also explore whether consistent transient bacteremia occurs in healthy horses unrelated to specific procedures. Conclusions This study demonstrated that bacteria can be cultured from blood samples and bacterial DNA can be detected via 16S rDNA sequencing in clinically healthy horses undergoing dental prophylaxis. However, whether these findings reflect true bacteremia, natural transient bacterial presence, or contamination is unclear. The observed differences in bacterial families post-procedure may relate to either genuine biological fluctuations or contamination artifacts. Further controlled research is needed to clarify these findings and their clinical implications. Declarations The authors have no financial or ethical conflicts of interest to declare. The authors have no funding to declare. Animal use was performed in accordance with the institutions Animal Care and Use policies and approval (IACUC-A2023-02-037). References: Arndt, S., Kilcoyne, I., Heney, C.M., Wong, T.S. and Magdesian, K.G. (2021) Bacterial meningitis after dental extraction in a 17-year-old horse. Canadian Veterinary Journal 62, 403–407. Borkent D., Reardon R.J.M., McLachlan G., Glendinning L., Dixon P.M. (2020) A Microbiome Analysis of Equine Peripheral Dental Caries Using next Generation Sequencing. Equine Vet. J. 52:67–75. Gao, W., Chan, Y., You, M., Lacap-Bugler, D. C., Leung, W. K., and Watt, R. M. (2016) In-depth snapshot of the equine subgingival microbiome. Microbial pathogenesis , 94 , 76-89. Glickman LT, Glickman NW, Moore GE, Goldstein GS, Lewis HB. 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Figure legends: Figure 1: A) Bar plot showing the number of horses in which each bacterial family was detected at baseline (T0) at >0 relative abundance. Of the 156 bacterial families identified across all samples, only 12 were present in ≥5 horses. B) Heatmap displaying the relative abundance of these 12 families across the 20 horses at baseline (T0). Values of zero are shown in white; darker blue shading indicates higher relative abundance. Figure 2. Global and within-sample bacterial DNA patterns across time points following dental prophylaxis. A) Weighted UniFrac principal coordinates analysis (PCoA) of bacterial DNA detected in blood samples at all time points (T0, T1, T30, T60, T24). Samples from different time points were intermixed with no visible clustering or separation, indicating no detectable global shift in community structure following dental prophylaxis. B) Alpha diversity metrics (Observed features and Shannon index) for each time point. Diversity values overlapped broadly among all sampling times, and no statistically significant differences in richness or diversity were detected between baseline and any post-procedure point. Together, these results show that the overall detectable bacterial DNA profile in blood remained stable over time. Figure 3. Heatmap of log₂ fold-changes for bacterial families that were significantly differentially abundant at one or more post-procedure time points (T1, T30, T60, T24) compared with baseline (T0). Each row represents a bacterial family and each column represents a sampling time point. Colors reflect the magnitude and direction of change, with red indicating increased relative abundance, blue indicating decreased relative abundance, and white indicating little to no change. Grey cells denote time points at which the family was not identified as significantly differentially abundant. Values are based on DESeq2 log₂ fold-change estimates, with significance defined as an adjusted p-value ≤ 0.05. Clustering was disabled to maintain the observed temporal patterns across families. Table 1. Summary of Blood Culture Positivity Across Sampling Times Table 1 shows the number of horses testing positive for blood cultures at each sampling time summarizing the patterns of positivity, including horses positive at multiple timepoints, consistently negative, and intermittently positive, illustrating variability in culture results over the study period. Counts of Horses Testing Positive at Each Time Point (n = 20) T0 (Baseline) 8 Completion 0 6 Completion 30 8 Completion 60 9 Completion 24 7 Positive at 2 time points 10 Positive at all 5 time points 2 Consistently negative 1 Positive only once Intermittent positives (3-4 times) Table 2: Summary of Dental Culture Findings Table 2: Shows the presence of bacterial species in blood cultures across multiple sampling times, with Gram-positive bacilli, particularly Bacillus altitudinis/pumilis , consistently dominant. Gram-positive cocci, especially staphylococci, gradually emerge as secondary members, while Gram-negative bacteria and yeast appear only sporadically and in low abundance. Timeline of Key Bacteria Across Timepoints Bacillus altitudinis/pumilis ✔ ✔ ✔ ✔ ✔ Bacillus megaterium / Priestia megaterium ✔ ✔ Bacillus licheniformis / Paenibacillus pabuli ✔ Bacillus cereus group ✔ Staphylococcus xylosus ✔ ✔ Staphylococcus succinus ✔ Staphylococcus equorum ✔ Staphylococcus saprophyticus / aprophyticus ✔ Brevibacterium epidermidis ✔ ✔ Gram-negative bacilli ( Enterococcus casseliflavus , Acinetobacter lwoffii ) ✔ ✔ Yeast ✔ ✔ Other Gram-positive cocci (unspecified) ✔ ✔ ✔ ✔ Other Gram-positive bacilli (unspecified) ✔ ✔ ✔ ✔ ✔ Information & Authors Information Version history V1 Version 1 16 December 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Authors Affiliations Allison Dockery 0009-0000-5181-3413 [email protected] University of Georgia College of Veterinary Medicine View all articles by this author Canaan Whitfield-Cargile 0000-0002-9743-8783 University of Georgia College of Veterinary Medicine View all articles by this author Vanessa Knopp University of Georgia College of Veterinary Medicine View all articles by this author Taylor Sinay University of Georgia College of Veterinary Medicine View all articles by this author Metrics & Citations Metrics Article Usage 169 views 95 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Allison Dockery, Canaan Whitfield-Cargile, Vanessa Knopp, et al. Bacteremia in Horses Undergoing Routine Dental Prophylaxis: Before, During, and After the Procedure. Authorea . 16 December 2025. 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