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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Meat Safety and Quality » Research » Publications at this Location » Publication #315665

Title: Variations in the fecal occurrences of antimicrobial-resistant bacteria are greater between seasons than between "raised without antibiotics" and "conventional" cattle production systems

Author
item Schmidt, John
item Agga, Getahun
item Bosilevac, Joseph
item Wheeler, Tommy
item Arthur, Terrance

Submitted to: American Society for Microbiology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 3/31/2015
Publication Date: 5/11/2015
Citation: Schmidt, J.W., Agga, G.E., Bosilevac, J.M., Wheeler, T.L., Arthur, T.M. 2015. Variations in the fecal occurrences of antimicrobial-resistant bacteria are greater between seasons than between "raised without antibiotics" and "conventional" cattle production systems.[Abstract] 4th American Society for Microbiology Conference on Antimicrobial Resistance in Zoonotic Bacteria and Foodborne Pathogens. S7:4,p.102.

Interpretive Summary:

Technical Abstract: The objective of this study was to compare, over a year, fecal occurrences of antimicrobial-resistant bacteria (ARB) in fed-cattle between two production systems: "raised without antibiotics" (RWA) and “conventional” (CONV). Feces were recovered from colons at a commercial beef processing plant obtained during monthly visits from February 2014 to January 2015. A total of 359 and 360 samples were obtained from RWA and CONV cattle, respectively. Samples were equally distributed by month and production system among 72 lots. For 8 of 12 months, 3rd-generation cephalosporin-resistant (3GCr) E. coli prevalences did not differ (P > 0.05) between CONV and RWA, but the overall 3GCr E. coli prevalence was higher (P < 0.05) in CONV (47.5%) than RWA (34.8%). For both production systems, 3GCr E. coli prevalences were higher (P < 0.05) in May to October (CONV = 69.4%, RWA = 63.3%) than in November to April (CONV = 25.6%, RWA = 6.1%). In 8 of 12 months trimethoprim-sulfamethoxazole-resistant (COTr) E. coli prevalences did not differ (P > 0.05), but the overall COTr E. coli prevalence was higher (P < 0.05) in CONV (71.4%) than in RWA (60.7%). The overall mean COTr E. coli concentration was higher (P < 0.05) in CONV (0.47 log CFU/g) than RWA (0.05 log CFU/g). Four of the monthly COTr E. coli concentrations were higher (P < 0.05) in CONV and 2 were higher (P < 0.05) in RWA. For both production systems, COTr E. coli prevalences and concentrations were higher (P < 0.05) in May to October (CONV = 97.8%, 1.45 log CFU/g; RWA = 78.3%, 0.70 log CFU/g) than in November to April (CONV = 45.0%, -0.50 log CFU/g; RWA = 43.0%, -0.60 log CFU/g). The overall erythromycin-resistant (ERYr) Enterococcus prevalence was higher (P < 0.05) in CONV (96.4%) than RWA (80.5%), but in 8 of 12 months, prevalences did not differ (P > 0.05) between production systems. The mean ERYr Enterococcus concentration was higher (P < 0.05) in CONV (1.93 log CFU/g) than in RWA (0.74 log CFU/g). For both production systems, ERYr Enterococcus concentrations were higher (P < 0.05) in May to October (CONV = 2.40 log CFU/g, RWA = 1.53 log CFU/g) than in November to April (CONV = 1.47 log CFU/g, RWA = -0.06 log CFU/g). This study suggests that seasonal effects have a more pronounced impact on fecal ARB occurrences in fed-cattle than production system because, in general, the seasonal differences in the occurrences of ARB were greater than the differences between production systems.