Prevalence and antimicrobial susceptibility of bacterial isolates from horses with synovial sepsis: A cross-sectional study of 95 cases.
Authors: Robinson C S, Timofte D, Singer E R, Rimmington L, Rubio-Martínez L M
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Bacterial Isolates and Antimicrobial Susceptibility in Equine Synovial Sepsis Whilst bacterial culture remains the diagnostic gold standard for synovial sepsis, results typically take over 24 hours to obtain, forcing clinicians to initiate empirical antimicrobial therapy based on educated guesswork. Robinson and colleagues examined nine years of microbiology records from a referral hospital, analysing 114 bacterial isolates from 95 horses with confirmed synovial infection to establish evidence-based guidance for initial treatment selection. Gram-positive bacteria dominated (75% of cases), with *Staphylococcus aureus* accounting for just over half of all isolates; Gram-negative organisms represented 25% of cases, and anaerobic *Clostridium* species appeared rarely at 3%. Tetracyclines (oxytetracycline and doxycycline) demonstrated the broadest spectrum effectiveness at 70–100% against Gram-positive organisms and 20–100% against Gram-negative bacteria, while trimethoprim-sulphamethoxazole and gentamicin showed more variable efficacy (50–88% against both groups); among protected antimicrobials, ceftiofur and enrofloxacin achieved susceptibility in 70–90% and 80% of isolates respectively. These findings validate current first-line recommendations and provide practitioners with a rational framework for choosing empirical therapy in synovial sepsis cases, pending culture and sensitivity results—particularly valuable given the time-critical nature of joint infections in equine medicine.
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Practical Takeaways
- •When treating equine synovial sepsis empirically before culture results, tetracyclines, trimethoprim-sulphamethoxazole, or gentamicin are suitable first-line choices based on local prevalence data from this cohort
- •Expect Gram-positive bacteria (especially Staphylococcus aureus) in 75% of synovial infections; cover accordingly while awaiting culture confirmation
- •Protected antimicrobials like ceftiofur and enrofloxacin offer excellent coverage (70-90% and 80% respectively) if first-line options fail or resistance is suspected
Key Findings
- •Gram-positive bacteria were isolated in 75% of cases, with Staphylococcus aureus accounting for 52% of all isolates
- •Tetracyclines (oxytetracycline and doxycycline) showed 70-100% efficacy against Gram-positive bacteria and 20-100% against Gram-negative organisms
- •Ceftiofur was effective against 70-90% of all bacterial isolates and enrofloxacin against 80% of isolates
- •Trimethoprim-sulphamethoxazole and gentamicin showed 50-88% efficacy against both Gram-positive and Gram-negative bacteria