Streptococcus equi culture prevalence, associated risk factors and antimicrobial susceptibility in a horse population from Colombia.

The objectives of this study were to determine the prevalence of S. equi in a horse population in Colombia, to determine the risk factors associated with its detection in the guttural pouches and to report the antimicrobial susceptibility of the isolates. Fifteen farms and 137 horses >6 months of age were enrolled. Sampling was randomly, stratified and proportional to the population size of each farm. The guttural pouch (GP) was swabbed via endoscopic guidance and culture was performed. DNA extraction and conventional PCR were performed in colonies compatibles with S. equi, the PCR products were sequenced and subjected to BLAST analysis. Antimicrobial drug sensitivity was assessed using an antimicrobial disc diffusion assay including penicillin, ceftiofur, trimethoprim-sulfamethoxasole (TMS), enrofloxacin and oxytetracycline. A mixed logistic regression model was constructed to evaluate risk factors associated with the presence of S. equi. The S. equi culture prevalence in the GP was 15%; 13.5 % for S. equi subsp. equi and 1.5% for S. equi subsp. zooepidemicus. History of travel was associated with the presence of S. equi, whereas every 1-year increase in age decreased the risk for S. equi detection in the GP. All isolates were susceptible to TMS, ceftiofur and penicillin, but resistant to enrofloxacin and oxytetracycline. S. equi is present in horses in Colombia, with a high prevalence and appear to be endemic in the tested population. Younger horses and horses with recent history of travelling had higher odds of testing positive for S. equi in swabs of the GP.