Advisor: Dr. Sherman Hendrix
The environment of an equine veterinary hospital is likely to have microbial populations related to the flora of the horse. Bacterial species within the family Enterobacteriaceae are part of the horse's intestinal flora and they are also responsible for about 50% of all nosocomial infections. Antibiotic resistance among opportunistic bacteria is a serious concern, and understanding the antibiotic and disinfectant resistance of a specific veterinary practice's enteric bacteria community could lead to better sanitization techniques and treatment of nosocomial infections. In addition, it has been shown that use of some disinfectants, such as pine-oil, can select for bacteria which are resistant to several antibiotics. The antibiotic and disinfectant resistance of selected enteric bacteria cultured from stalls at an equine orthopedic surgery hospital in Monkton, Maryland was investigated in this study. The selection of antibiotic resistant bacteria by pine-oil formulations was also be examined. Fifteen bacterial isolates were cultured from five different horse stalls, and 20% of these isolates were resistant to three or more antibiotics. These results are similar to those found in other studies. In a modified use dilution test, sodium hypochlorite, Betadine® and chlorhexidine were found to be effective hospital disinfectants. Pine-sol® was found to be an ineffective disinfectant and it also selected for Kluyvera sp. isolates and E. coli isolates which were resistant to multiple antibiotics. The antibiotic resistance of these isolates may be due to the over-expression of the mar and acrAB genes. Further studies should be conducted to determine a dilution of Pine-sol® which does not allow for an increase in antibiotic resistant bacteria.