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

This research paper studied the prevalence and risk factors of Streptococcus equi, a bacterium known to cause infection in horses, in a horse population in Colombia. The paper also investigated antibiotic resistance levels in the bacteria.

Research Methods and Objectives

• The paper had three main objectives:
  • To find out the prevalence of S. equi in Colombia’s horse population.
  • To identify risk factors associated with the bacterium’s presence in the guttural pouches of horses.
  • To identify the antimicrobial susceptibility of the S. equi strains detected.
• Sampling was conducted randomly on fifteen farms and among 137 horses, aged more than 6 months. It was proportional and stratified to each farm’s horse population size.
• The guttural pouch, a pocket in the horse’s throat, was swabbed under endoscopic guidance for sampling, and cultures were subsequently performed.
• DNA was extracted from the colonies resembling S. equi to perform PCR (Polymerase Chain Reaction) analysis. The PCR products were to be sequenced and subjected to BLAST analysis – a technique to identify genetic sequences.
• The antibiotic sensitivity of the isolates was tested using an antimicrobial disc diffusion assay involving multiple drugs like penicillin, enrofloxacin, oxytetracycline, trimethoprim-sulfamethoxasole (TMS), and ceftiofur.
• A mixed logistic regression model was used to monitor risk factors influencing the presence of S. equi.

Outcome

• The study revealed a 15% prevalence of S. equi culture in the guttural pouch. The breakdown showed 13.5% for S. equi subsp. equi and 1.5% for S. equi subsp. zooepidemicus.
• The presence of the pathogen was correlated with a history of travel. Additionally, each one-year increase in a horse’s age decreased the risk for S. equi detection.
• In terms of antibiotic susceptibility, all the S. equi isolates were susceptible to TMS, ceftiofur, and penicillin, but resisted enrofloxacin and oxytetracycline.
• The results confirm the presence of S. equi in Colombian horses with a high prevalence rate, suggesting that the bacterium may be endemic in the studied population.
• Younger horses and horses that recently travelled had higher chances of testing positive for S. equi.

Importance of the Study

• This study helps understand the extent of S. equi prevalence in a key South American horse population, which may help inform treatment strategies and prevention measures.
• The finding of antibiotic resistance points to the need for judicious use of antibiotics in this setting.
• The results also underscore the importance of controlling and monitoring the movement of horses, given the established link with recent travel.