|Cao, Huilin - U.s. Department Of Agriculture (USDA)|
|Seon-woo, Kim - U.s. Department Of Agriculture (USDA)|
|Hovingh, Ernest - Pennsylvania State University|
|Van Kessel, Jo Ann|
Submitted to: American Society for Microbiology Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/19/2017
Publication Date: 5/30/2017
Citation: Cao, H., Seon-Woo, K., Hovingh, E., Van Kessel, J.S. 2017. Epidemiology of 3rd generation cephalosporin-resistant Escherichia coli on dairy farms. American Society for Microbiology Branch Meeting. Baltimore, MD on Mary 30, 2017.
Technical Abstract: Dairy cattle have been identified as a reservoir for 3rd generation cephalosporin (3GC)-resistant Escherichia coli. We previously identified 3GC-resistant E. coli from manure composite samples of calves and cows in a survey of 80 farms in Pennsylvania. Resistant strains were most frequently isolated from the feces of pre- and post-weaned calves than from lactating and dry cows. The objective of this study was to examine the extent to which strains are shared among different age groups on the same farm and among different farms. A total of 71 E. coli isolates from pre-weaned calves, post-weaned calves, dry cows, and lactating cows on 14 farms were characterized and compared. Based on PCR analysis, CMY beta-lactamase was the most common (79%) 3GC-resistance-conferring genotype; CTX-M extended-spectrum beta-lactamase-producing E. coli were also identified. Pulse-field gel electrophoresis (Xbal) digestion profiles showed that 3GC-resistant bovine E. coli were highly heterogeneous, with 46 genetic subtypes (<95% similarity) observed among the isolates. Isolates with indistinguishable digestion profiles (100% similarity) from different groups of animals within the same farm were observed on 9 farms. Additionally, four clonal isolates were found in two farms that were located in adjacent counties, indicating potential for dissemination of 3GC-resistant E. coli between farms or in the environment. Results of the previous study determined that 3GC-resistant E. coli represented a larger proportion of the E. coli population in calf feces than in adult cow feces. This study provides evidence of clonal strains harbored by young and mature animals on the same farm, and suggests that steps to mitigate resistant populations in the calves may also impact the resistant population in adult cows.