Adsa Logo White Adsa Title White

Antimicrobial resistance in fecal commensal bacteria isolated from dairy cows in California.

E. Abdelfattah

Events

06-22-2020

Abstract:

71
Antimicrobial resistance in fecal commensal bacteria isolated from dairy cows in California.
E. Abdelfattah*1, P. Ekong1, E. Okello1,2, T. Chamchoy1, B. Karle3, R. Black4, D. Sheedy1, W. El-Ashmawy1, D. Williams1, D. Califano1, L. Duran1, J. Ongom1, B. Byrne5, T. Lehenbauer1,2, S. Aly1,2. 1Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California Tulare, CA, 2Department of Population Health & Reproduction, School of Veterinary Medicine, University of California Davis, CA, 3Cooperative Extension, Division of Agriculture and Natural Resources, University of California Orland, CA, 4Cooperative Extension, Division of Agriculture and Natural Resources, University of California Santa Rosa, CA, 5Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California Davis, CA.

The objective of study was to describe antimicrobial resistance (AMR) patterns in Escherichia coli and Enterococcus spp. isolated from adult cows, following the implementation of Senate Bill 27. The 10 study dairies were distributed across California's 3 milk sheds: Northern CA (NCA), Northern San Joaquin Valley (NSJV) and the Greater Southern California (GSCA). Individual cow fecal samples were collected monthly from pre-partum to 120 d in milk from 2 cohorts each of 12 cows enrolled on each study dairy during the winter and summer. Isolated E. coli and Enterococcus spp. were tested for antimicrobial susceptibility to determine the minimum inhibitory concentration. Antimicrobial susceptibility testing was completed on 2,171 E. coli and 2,158 Enterococcus isolates. The proportion of AMR was calculated in Stata with a P-value < 0.05 was the threshold of significance. None of the E. coli isolates and 37.3% of Enterococcus isolates were pan susceptible to all drug classes tested. The E. coli AMR to tilmicosin (99.9%), tylosin (99.8%), tiamulin (98.9%), florfenicol (83.3%) gamithromycin (74.0%), and tildipirosin (20.51%) was common, while E. coli AMR to ampicillin (1.1%), ceftiofur (1.9%), danofloxacin (4.0%), enrofloxacin (3.3%), gentamicin (0.3%), and neomycin (1.6%) was rare. Like E. coli, Enterococcus spp. were highly resistant to tildipirosin (50%), tilmicosin (48%), tiamulin (42%), and florfenicol (46%). In addition, enterococci showed a lower rate of resistance to ampicillin (0.23%), and penicillin (0.20%). Multidrug resistance (MDR) (resistance to ≥3 antimicrobial classes) was observed in 38% of E. coli isolates, and 39% of Enterococcus spp. isolates recovered during the winter season showed higher MDR prevalence compared with the summer isolates (P < 0.01). A higher prevalence of MDR was observed in NSJV and GSCA compared with NCA (P < 0.01). Our findings show high rates of AMR to drugs commonly administered to calves. Conversely, very low resistance was observed for drugs used for adult dairy cows such as cephalosporins, and penicillin. Overall, our findings identified important differences in AMR by antimicrobial classes, region and season.

Keywords: antimicrobial resistance, cattle.

Biography: I am currently a postdoctoral scholar in Dairy Epidemiology Laboratory, University of California, Davis, Veterinary Medicine Training and Research Centre (VMTRC) in Tulare, CA. I am interested in using an epidemiological approach to investigate risk factors, including aspects of housing and management, associated with the health and/or behavior of agriculture animals. My general academic interest is to use the systems modeling and statistical methods for the study of animal health and welfare, using large-scale epidemiological experiments. I am currently leading a large-scale project to understand the association between Antimicrobial treatments at dry-off period and antimicrobial resistance in adult cattle on California dairies.