Antimicrobial susceptibility of microorganisms isolated from equine orthopedic patients

Positive cultures were obtained from 60 equine orthopedic cases during a 12 year period (1974-1985). These cases consisted of 34 long or cuboidal bone fractures, 13 arthrotomy/arthroscopy procedures for removal or internal fixation of a fracture, 7 proximal splint bone fractures, and 6 facial or mandibular fractures. Excluding the 13 arthrotomies, only 10 (21%) of the 47 were open fractures. Multiple organisms were isolated from 36 cases (20 long or cuboidal bone fractures, 7 splint bone fractures, 5 mandibular fractures, and 4 intra-articular fractures). Of the 142 isolates, 35 (24%) were members of the family Enterobacteriaceae, 33 (23%) Streptococcus spp., and 25 (18%) Staphylococcus spp. with the majority being coagulase positive (65%). Other organisms isolated were Pseudomonas spp. (16, 11%), obligate anaerobes (11, 7%), and Actinobacillus spp. (7, 5%). the remaining 10% consisted of Pasteurella spp., Bacillus spp., Corynebacterium spp., Micrococcus spp., and Actinomyces spp. When comparing results between two time periods (1974-1979 and 1980-1985) there was an increase in the percentage of coagulase positive staphylococci isolates resistant to all antimicrobics tested except oxacillin and amikacin, and Escherichia coli isolates were resistant to all but amikacin. For Pseudomonas spp., resistance to gentamicin increased in the second time period (1980-1986). During the initial time period (1974-1979) culture tests for obligate anerobes were not conducted until 1975. No anerobes were cultured during those initial 5 years; however, one third of those isolated after 1980 were resistant to penicillin and ampicillin.(ABSTRACT TRUNCATED AT 250 WORDS)