Evaluation of an automated blood culture system for the isolation of bacteria from equine synovial fluid.

This research evaluates the efficacy of an automated blood culture system in isolating bacteria from synovial fluid in horses. The study found that this system is efficient in detecting bacterial infections, combining rapid detection with specialized medium enrichment.

Study Design and Objective

• The objective of the research was to assess how an automated blood culture system could be used for identifying microorganisms from infected equine synovial fluid, commonly found in severely inflamed joint problems in horses.

Methodology

• 220 samples were collected from severely inflamed synovial joints and classified into two categories – presumably infected (group A: n=149) and not infected (group B: n=71). Criteria for this classification were based on clinical history, observable clinical signs and cytological analysis of the synovial fluid.
• These samples were then inoculated into blood culture bottles and post-incubation, they were sub-cultured onto agar media. Sub-culturing serves to provide confirmation of the results and facilitates comprehensive bacterial identification.

Findings

• Microorganisms were found in 107 samples from the presumably infected group (72%) and in three samples from the group presumed not infected (4.2%).
• The overall detection system identified 117 bottles as infected and 103 as uninfected, but there were nine false positives and two false negatives noted.
• The median detection time for different types of bacteria were also calculated: Gram-positive bacteria had a median detection time of 14.3 hours, Gram-negative bacteria had a median time of 8.8 hours, and fungus had a median detection time of 72.0 hours.

Conclusion

• The study concludes that using automated culture systems for detecting infected synovial fluid combines the benefit of rapid detection with enrichment in a specialised medium. This could potentially offer a reliable, quicker method for identifying bacterial infections in equine synovial fluid.