The Bacteria Isolated from the Skin of 20 Horses at a Veterinary Teaching Hospital

The objective of this study was to isolate bacteria on the skin of the proximal to distal equine limb to guide the practitioner in the selection of prophylactic antimicrobial protocols. This prospective study involved 20 client-owned horses that were admitted to the Veterinary Teaching Hospital for routine elective surgery. Each horse spent between 12 and 36 hours at our hospital before sampling. Samples were collected from the skin of the left mid-thorax and the dorsal aspect of nine joints on the left side of each horse: front and hind coffin and fetlock joints, carpi, elbows, shoulders, hocks, and stifles. Samples were cultured aerobically and speciated when possible. When evaluating bacterial composition by location, a 40% difference was considered clinically significant. When comparing proximal sites above the fetlock to distal sites, the odds of isolating gram-positive bacteria were 1.23 times (P = .0124) higher at proximal sites; the odds of isolating coliform bacteria were 1.32 times (P = .023) higher at distal sites; and the odds of isolating a common septic arthritis pathogen were 1.16 times (P = .018) higher at distal sites. Coagulase-positive Staphylococcus was not isolated in this study. All comparisons between sites and between the proximal and distal limb were <40%, and thus were not considered clinically significant. No coagulase-positive Staphylococcus was isolated from any of the 200 sites in this study, suggesting that iatrogenic infections by that organism may not be because of preexisting flora. These data suggest that antibiotic prophylaxis targeting preexisting normal flora should be similar regardless of the area of interest on the limb.