Bacteremia in horses undergoing routine dental prophylaxis: Before, during, and after the procedure

BACKGROUND: Transient bacteremia after dental procedures is well-documented in the literature, but the prevalence and clinical significance in horses remains largely unexplored. OBJECTIVES: To assess whether routine dental prophylaxis in clinically healthy horses is associated with detection of bacteria in blood, using culture and 16S rDNA sequencing. Our central hypothesis is that a percentage of horses would demonstrate detectable but transient bacteremia in the immediate post-procedural period following dental prophylaxis. STUDY DESIGN: Prospective, observational study. METHODS: Venous blood samples from 20 horses without evidence of significant dental disease were collected before, immediately after, 30 min, 60 min, and 24 h post-procedure and submitted for routine aerobic and anaerobic bacterial culture and 16S rDNA sequencing. RESULTS: Data were analysed for normality by Shapiro-Wilk and Kruskal-Wallis analysis of variance (ANOVA) on ranks was performed on non-normally distributed data. Sixteen of twenty 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 eight bacterial families with increased and three 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 low-biomass nature of blood samples limit interpretation. CONCLUSIONS: Culturable bacteria and bacterial DNA were detected from blood samples of clinically healthy horses before and after routine dental prophylaxis, though overall culture positivity and community diversity remained stable. Differential abundance analyses identified subtle post-procedural changes in low-abundance taxa; however, without negative controls, these findings may reflect biological variation or contamination and should be interpreted cautiously.