Validation of a screening method for the detection of colistin-resistant E. coli containing mcr-1 in feral swine feces

Authors

Jeffrey C. Chandler, NWRC APHIS USDAFollow
Alan B. Franklin, USDA-APHIS-WS National Wildlife Research CenterFollow
S. N. Bevins, US Department of Agriculture–National Wildlife Research CenterFollow
Kevin T. Bentler, National Wildlife Research CenterFollow
Jonas Bonnedahl, Linköping University, SwedenFollow
Christina A. Ahlstrom, USGS Alaska Science Center, AnchorageFollow
Bledar Bisha, University of WyomingFollow
Susan A. Shriner, USDA/APHIS/WS National Wildlife Research CenterFollow

Document Type

Article

Date of this Version

2020

Citation

Journal of Microbiological Methods 172 (2020) 105892

doi 10.1016/j.mimet.2020.105892

Comments

US govt

Abstract

A method was developed and validated for the detection of colistin-resistant Escherichia coli containing mcr-1 in the feces of feral swine. Following optimization of an enrichment method using EC broth supplemented with colistin (1 μg/mL) and vancomycin (8 μg/mL), aliquots derived from 100 feral swine fecal samples were spiked with of one of five different mcr-1 positive E. coli strains (between 10⁰ and 10⁴ CFU/g), for a total of 1110 samples tested. Enrichments were then screened using a simple boil-prep and a previously developed real-time PCR assay for mcr-1 detection. The sensitivity of the method was determined in swine feces, with mcr-1 E. coli inocula of 0.1–9.99 CFU/g (n=340), 10–49.99 CFU/g (n=170), 50–99 CFU/g (n=255), 100–149 CFU/g (n=60), and 200–2200 CFU/g (n=175), which were detected with 32%, 72%, 88%, 95%, and 98% accuracy, respectively. Uninoculated controls (n = 100) were negative for mcr-1 following enrichment.