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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 - Mick
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.