Objectives: Our objectives were: a) to establish a selective method for surveillance of gentamicin-resistant (GNRE), ciprofloxacin-resistant (QRE) and ESBL-producing Enterobacteriaceae (ESBLPE) in livestock; b) to measure the prevalence of these ARE in a national survey of beef cattle and c) to compare prevalence as measured by the non-selective and selective methods.
Methods: This was a point-prevalence study conducted from July to October 2013 in Israel. Stool samples from individual cows were collected. For the selective surveillance method (SSM), broth aliquots were sub-cultured onto selective media: MacConkey agar with either gentamicin or ciprofloxacin for GNRE and QRE, respectively; CHROMAgar ESBL™ plates for ESBLPE; CHROMAgar VRE™ plates for VRE. The non-selective surveillance method (NSSM) was done by sub-cultured of the broth aliquots were onto MacConkey agar. E. coli isolates were randomly selected for testing.
Results: The study included 1226 cows from 40 farms. Using SSM, GNRE, QRE and ESBLPE were identified in 840 (68.5%), 609 (49.7%) and 291 (23.7%) samples, respectively. VRE were not detected. Using SSM in the subset of 128 samples, GNRE QRE and ESBLPE were identified in 40 samples (31.2%) each. Using NSSM, GNRE QRE and ESBLPE were identified in 3 (2.3%), 6 (4.6%) and 1 (0.7%) samples, respectively. Using the NSSM, non-susceptibility to other agents was high: tetracycline-54.6%, streptomycin- 25.7% and trimethoprim-sulfamethoxazole-25%.
Conclusions: Our study revealed a high prevalence of GNRE, QRE and ESBLPE carriage in beef cattle. Using SSM is crucial for accurate measurement and should be used for AMR surveillance of antimicrobials with epidemiologic importance.
