Location: Food and Feed Safety Research
Title: Disinfectant and antibiotic susceptibility profiles of Escherichia coli O157:H7 strains from cattle carcasses, feces, and hides and ground beef from the United States Authors
|Nagaraja, T -|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 21, 2012
Publication Date: January 2, 2013
Citation: Beier, R.C., Poole, T.L., Brichta-Harhay, D.M., Anderson, R.C., Bischoff, K.M., Hernandez, C.A., Bono, J.L., Arthur, T.M., Nagaraja, T.G., Crippen, T.L., Sheffield, C.L., Nisbet, D.J. 2013. Disinfectant and antibiotic susceptibility profiles of Escherichia coli O157:H7 strains from cattle carcasses, feces, and hides and ground beef from the United States. Journal of Food Protection. 76:6-17. Interpretive Summary: Many different kinds of disinfectants are used on farms, food processing plants, hospitals, and homes. In each of these places there is also widespread use of a variety of antibiotics. Little is known about the impact of disinfectants on the spread of antibiotic resistance. Certain bacteria named Escherichia coli O157:H7 are a major health hazard that can be found in ground beef. We found that E. coli O157:H7 isolated from cattle feces, hides, carcasses, and ground beef had a low incidence of antibiotic resistance (14%) and a low level of resistance to disinfectants (20%). There was no observed correlation between disinfectant resistance and antibiotic resistance. We observed 6.1% inducible resistance to disinfectants and only 1.4% inducible resistance to antibiotics. The highest amount of inducible resistance was to disinfectants used in dairies, restaurants, and food processing plants. These bacteria had high minimum inhibitory concentrations (MICs) to acetic, lactic, and citric acids. The observed correlation of the concentration of dissociated organic acids and MICs strongly suggests that the inhibition of E. coli O157:H7 by these acids was primarily due to the dissociated form of the acids. This information is important in understanding the way bacteria are affected by disinfectants and may help in pathogen control during food processing.
Technical Abstract: The disinfectant and antibiotic susceptibility profiles of 344 Escherichia coli O157:H7 isolates from cattle feces, hide, carcass, and ground beef from different areas of the United States were determined. Overall, a low incidence of antibiotic resistance was observed (14%). The highest-incidence of resistance observed was to sulfisoxazole (10.5%), tetracycline (9.9%), streptomycin (7%), and chloramphenicol (4.9%). Four isolates were found to be resistant to eight antibiotics (two isolated from ground beef and one each from hide and preevisceration carcass swabs of cull cattle at harvest). PFGE analysis of the E. coli O157:H7 isolates revealed that they fell into two major groups (designated 1 and 2) composed of 17 and 20 clusters, respectively. Clusters 1A, 1B, 1C, and 1G.1 were associated with multi-drug resistant (MDR) isolates. There was no observed correlation between disinfectant resistance and antibiotic resistance. Sixty-nine (20%) of the 344 isolates were resistant to chlorhexidine, benzalkonium chloride, or had elevated MICs to benzyldimethyldodecylammonium chloride. Inducible resistance was observed at elevated levels of antibiotics (1.4%) and disinfectants (6.1%). The highest-rate of inducible resistance was observed to OdoBan, quaternary ammonium chloride components, and to the surface disinfectants F25, FS512, and MG used in dairies, restaurants, and food processing plants. Inducible resistance could allow the presence of bacteria where they should have been removed by disinfection. High-MICs (1024–4096 µg/ml) were found for acetic, lactic, and citric acids. The decreasing order of acid potency based on MICsmolar was acetic, citric, and lactic acid. The correlation of the concentration of dissociated organic acids and MICsmolar strongly suggests that the observed inhibition of E. coli O157:H7 was primarily due to the dissociated form of the acids.