Antimicrobial resistance, antimicrobial use and infection control in community small animal veterinary hospitals in southern Ontario

This thesis is a study of components of the epidemiology of antimicrobial resistance in companion animals. The effect of antimicrobial treatment on the occurrence of antimicrobial resistance in fecal Escherichia coli isolates, antimicrobial use by companion animal veterinarians and the recovery of environmental bacteria from companion animal veterinary practices were investigated. The effect of antimicrobial treatment on the occurrence of antimicrobial resistance was examined using a cohort design studying in dogs requiring treatment with amoxicillin-clavulanic acid, cephalexin, fluoroquinolones or penicillin. Resistance to amoxicillin-clavulanic acid, cefoxitin, ceftiofur and ceftriaxone in fecal E. coli from dogs was significantly associated with treatment with cephalexin. Also, isolation of fecal Clostridium difficile was significantly associated with treatment with amoxicillin-clavulanic acid. Antimicrobial use by companion animal veterinarians was investigated using journals recording diagnosed new disease events and associated treatments. Antimicrobials were the most frequently prescribed treatment. Non-topical (oral, parenteral) antimicrobials were the most common type of antimicrobial prescribed, and beta-lactams were the most frequently prescribed antimicrobial class. In dogs, 67% of new disease events associated with canine infectious tracheobronchitis were treated with antimicrobials. In cats, 70% and 74% of disease events associated with feline upper respiratory tract disease and feline lower urinary tract disease, respectively, were treated with antimicrobials. The recovery of environmental bacteria from community veterinary hospitals was investigated in a cross-sectional study. The proportion of hospitals with positive environmental samples were: E. coli-92%, C. difficile-58%, methicillin-resistant Staphylococcus aureus -9%, CMY-2 producing E. coli-9%, methicillin-resistant Staphylococcus pseudintermedius-7%, Salmonella-2%. Antimicrobial resistance in E. coli was infrequent, but several important potential pathogens were recovered: Canadian epidemic strains MRSA-2 and MRSA-5, and C. difficile ribotype 027. An evaluation of infection control practices demonstrated deficiencies that could be improved: development of formal infection control policies, use of isolation for infectious patients, and disinfectant selection for environmental disinfection. The overall study results suggest that use of common antimicrobials in companion animal practice and associated antimicrobial resistance may pose a risk to animal and human health, and that companion animal veterinary hospitals are a reservoir for environmental and antimicrobial resistant pathogens.