Bacterial culture of septic synovial structures of horses: does a positive bacterial culture influence prognosis?

This research study investigates the relationship between positive bacterial culture in synovial fluid of horses with septic synovitis and their prognosis. The findings suggest horses with a positive bacterial culture have a poorer chance of survival and return to function than those with a negative culture, with Staphylococcus aureus having a particularly negative impact on prognosis.

Research Objective

• The goal of this study was to determine the effect of synovial fluid culture, particularly the presence of bacteria, on the short and long-term prognosis of horses suffering from septic synovitis. Septic synovitis is a health issue in horses that entails an infection in the synovial fluid which can lead to pain, swelling and reduced function. By investigating whether a positive or negative bacterial culture influences survival and recovery rates, the study aims to better understand and potentially improve equine health management.

Methods

• Records of adult horses suspected of having septic synovitis from two equine referral hospitals were examined. The pool consisted of 206 horses for which synovial fluid was fully examined
• A diagnosis of septic synovitis was determined based on certain clinical, cytological and bacteriological parameters such as cell count and percentage of neutrophils.
• Long-term data was collected using telephone questionnaires.
• The statistical analysis of the outcomes was conducted using univariate analysis with Fisher’s exact test.

Results

• The research found that 20.9% of horses with positive bacterial culture had to be euthanized due to persistent synovitis, as compared to only 1.44% of those with negative bacterial cultures.
• Furthermore, overall survival and successful long-term return to functionality was 50% for horses with a positive bacterial culture, as opposed to a much higher 70.5% for horses with a negative culture.
• In horses that survived to be discharged, long-term functionality was not significantly different between culture positive and culture negative groups.
• When specifically looking at Staphylococcus aureus bacteria, it was found that while their presence didn’t affect short-term survival, the long-term return to functionality was significantly lower compared to when other bacteria were present.

Conclusions

• The findings of this research suggest that presence of bacteria in the synovial fluid of horses with septic synovitis negatively influences prognosis.
• Horses with a positive bacterial culture are less likely to survive and successfully return to function compared to those with a negative culture.
• The presence of Staphylococcus aureus was specifically noted to have a negative impact on long-term prognosis.