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.