Objective: To describe antimicrobial susceptibility testing practices of veterinary diagnostic laboratories in the United States and evaluate the feasibility of collating this information for the purpose of monitoring antimicrobial resistance in bacterial isolates from animals.
Design: Cross-sectional study.
Procedures: A questionnaire was mailed to veterinary diagnostic laboratories throughout the United States to identify those laboratories that conduct susceptibility testing. Nonrespondent laboratories were followed up through telephone contact and additional mailings. Data were gathered regarding methods of susceptibility testing, standardization of methods, data management, and types of isolates tested.
Results: Eighty-six of 113 (76%) laboratories responded to the survey, and 64 of the 86 (74%) routinely performed susceptibility testing on bacterial isolates from animals. Thirty-four of the 36 (94%) laboratories accredited by the American Association of Veterinary Laboratory Diagnosticians responded to the survey. Laboratories reported testing > 160,000 bacterial isolates/y. Fifty-one (88%) laboratories reported using the Kirby-Bauer disk diffusion test to evaluate antimicrobial susceptibility; this accounted for 65% of the isolates tested. Most (87%) laboratories used the NCCLS (National Committee for Clinical Laboratory Standards) documents for test interpretation. Seventy-five percent of the laboratories performed susceptibility testing on bacterial isolates only when they were potential pathogens.
Conclusions: The veterinary diagnostic laboratories represent a comprehensive source of data that is not easily accessible in the United States. Variability in testing methods and data storage would present challenges for data aggregation, summary, and interpretation.