Low prevalence of mobile colistin-resistance in U.S. meat, catfish, poultry and genomic characterization of a mcr-1 positive Escherichia coli strain

Authors: WANG, YAN - Chinese Center For Disease Control; HOU, NAXIN - Volunteer; JOHNSTON, JOHN - Food Safety Inspection Service (FSIS); SARREAL, CHESTER - Food Safety Inspection Service (FSIS); JAROSH, JOHN - Food Safety Inspection Service (FSIS); Hughes, Anna; Gu, Yong; He, Xiaohua

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2020
Publication Date: 6/16/2020
Publication URL: https://handle.nal.usda.gov/10113/6995513
Citation: Wang, Y., Hou, N., Johnston, J., Sarreal, C., Jarosh, J., Hughes, A.C., Gu, Y.Q., He, X. 2020. Low prevalence of mobile colistin-resistance in U.S. meat, catfish, poultry and genomic characterization of a mcr-1 positive Escherichia coli strain. Food Control. 118. https://doi.org/10.1016/j.foodcont.2020.107434.
DOI: https://doi.org/10.1016/j.foodcont.2020.107434

Interpretive Summary: Antimicrobial resistance has been a major human health issue, but the recent emergence of mobile colistin-resistance in bacteria isolated from a broad range of hosts is even more worrisome because colistin was considered a drug of last resort for bacterial infections. Timely investigation of the prevalence of colistin resistance in US agricultural products is critical in order to minimize its further spreading. In this study, we screened 5,169 animal-origin samples, including chicken, beef, pork, poultry and fish collected by FSIS and identified one bacterial strain from pork with an IncI2 plasmid bearing the mcr-1 gene. This is the first systemic and large-scale investigation of mobile colistin-resistance in US raw meat, the information obtained should be useful for trade negotiation and risk assessment.

Technical Abstract: This paper describes the results and outcomes of a survey conducted to investigate the prevalence of mcr-1 in 5,169 animal-origin samples collected by the USDA-Food Safety and Inspection Service between October 2018 and May 2019. Samples from chicken rinse (N=1,787), ground beef (N=1,369), beef trim (N=1,057), poultry (N=363), raw pork (N=416) and fish (N=177) were enriched in non-selective media and transferred to 96 well plates with a selection medium containing CaCl2, and colistin and vancomycin. A novel ELISA was used to screen for the mcr-1 gene product (MCR-1). Only a single colistin resistant Escherichia coli carrying mcr-1 gene was isolated from raw pork, which resulted in an overall mcr-1 prevalence in raw pork of 0.24% and less than 0.02% in the total samples tested. This study represents the first systematic and large-scale investigation of mcr-1 in U.S. meats, poultry, and fish and indicates that mcr-1 is rare in U.S. animal products. The positive isolate, Escherichia coli 2492 (EC2492), which was resistant to colistin with a MIC of 8 mg/L was further examined. The mcr-1 gene was located on an IncI2 type plasmid that carried no other virulence or resistance genes. Whole genome sequencing of EC2492 indicated that the isolate contained a 4.8 Mb chromosome and six plasmids. In silico analysis assigned EC2492 to ST101 and serotype O54:H21. The chromosome of EC2492 carried a class C AmpC beta lactamase and ten other resistance genes involved in antibiotic efflux. In conclusion, while the survey results indicated that mcr-1 is rare in U.S. meat foods, that one positive isolate was found suggests that continued vigilance to minimize further spread of mobile colistin resistance is warranted.