Equine synovial sepsis laboratory submissions yield a low rate of positive bacterial culture and a high prevalence of antimicrobial resistance.

This research study examines laboratory submissions for equine synovial sepsis, discovering that they yield a low rate of positive bacterial culture and a high prevalence of antimicrobial resistance. The study further explores variables that enhance the probability of a positive culture, common microbes associated, and their antimicrobial resistance patterns.

Study Methodology

• The study spanned twenty years (2000-2020) and involved synovial fluid, synovium, and bone samples from equine cases with suspected synovial sepsis. The samples were sent to the Cornell University Animal Health Diagnostic Center for microbial culture and antimicrobial sensitivity testing.
• A combination of univariable and multivariable analyses were utilized to figure out the impact of various factors on the likelihood of achieving a positive culture.
• Frequency distributions for isolated organisms and antimicrobial resistance were generated.
• The study also evaluated multidrug resistance patterns and associations using association rule mining.

Findings

• A 37.4% positive culture rate was noted for all samples, while the proportion of positive cultures among samples confirmed to be septic by a combination of clinical pathological variables and case details rose to 43%.
• It was found that submissions in blood culture vials were 1.7 times more likely to yield a positive culture compared to samples submitted in a serum tube.
• The structure sampled, the tissue submitted, and the age of the horse were all found to have an association with a positive culture.
• Staphylococcus spp, Streptococcus spp, and Enterococcus spp were the most commonly isolated microbes.
• The prevalence of multidrug resistance among gram-negative isolates decreased from 92% (2000 to 2009) to 76% (2010 to 2020), and from 60% to 52% for gram-positive isolates over the same periods.

Conclusions

• The study concluded that traditional sampling and culture methods of synovial fluid result in a low positive culture rate. This rate could potentially be increased by submitting samples in blood culture vials rather than serum tubes.
• The research also noted a high prevalence of antimicrobial resistance, though it seemed to be decreasing and did not increase from the first to the second decade for most genera.