While many veterinarians have long suspected that infected joints from which bacteria can be cultured result in a poorer outcome than joints from which no bacteria could be cultured, this hypothesis was recently substantiated by a group of United Kingdom researchers led by Tim Mair, BVSc, MRCVS, DEIM, DESTS, Dipl. ECEIM, of the Bell Equine Veterinary Clinic.
Infections of synovial structures such as joints, tendon sheaths, and bursae are both career- and life-threatening events. The hallmarks of an infected joint are heat, pain, effusion, and a rapidly developing and severe lameness.
Common bacterial culprits in joint infections are the enterobacteriaceae (gram-negative bacteria that normally inhabit the intestines, e.g., Salmonella and Escherichia coli), Streptococcus, and Staphylococcus. But for various reasons, bacteria are not always cultured from infected joints.
To determine the influence of synovial fluid culture results on the prognosis for horses treated for infected synovial structures, researchers reviewed medical records from 206 horses treated at the Royal veterinary College Equine Referral Hospital or Bell Equine Veterinary Clinic between 1993 and 2006.
Mair and coworkers found that:
- Positive bacterial cultures were obtained from 69/214 (32.2%) of the septic synovial structures;
- Significantly more horses with positive bacterial cultures 14/67 (20.9%) were euthanized than the 2/139 (1.44%) of horses with negative bacterial cultures;
- Horses with negative cultures were had significantly better survival and successful long-term return to function than horses with positive cultures, and
- Infection with Staphylococcus aureus was associated with decreased long-term return to function.
The authors did note, however, that "resolution of synovial sepsis is a multifactorial issue with conflicting data regarding many of the factors involved and, therefore, the use of positive bacterial cultures as major prognostic indicator in synovial sepsis is not warranted without further study."
The study, "Bacterial culture of septic synovial structures of horses: Does a positive bacterial culture influence prognosis?" will be published in an upcoming edition of the Equine Veterinary Journal. The full article is available free online.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.