Abstract
The rapid spreading of polymyxin E (colistin) resistance among bacterial strains through the horizontally transmissible mcr-1 and mcr-2 plasmids has become a serious concern. The emergence of these genes in Shiga toxin-producing Escherichia coli (STEC), a group of human pathogenic bacteria was even more worrisome, urging us to investigate the prevalence of mcr genes among STEC isolates. A total of 1000 STEC isolates, recovered from livestock, wildlife, produce and other environmental sources in a major production region for leafy vegetables in California during 2006-2014, were screened by PCR for the presence of plasmid-borne mcr-1 and mcr-2. All isolates tested yielded negative results, indicating if any, the occurrence rate of mcr-1/mcr-2 among STEC was very low in this agricultural region. This study provides valuable information such as sample size needed and methodologies for future surveillance programs of antimicrobial resistance.
MeSH terms
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Animals
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California / epidemiology
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DNA, Bacterial / genetics*
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Epidemiological Monitoring
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Escherichia coli Infections / epidemiology
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Escherichia coli Infections / microbiology
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Escherichia coli Infections / prevention & control
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Escherichia coli Proteins / genetics*
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Food Microbiology*
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Gene Transfer, Horizontal
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Humans
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Livestock / microbiology
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Plasmids / chemistry*
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Plasmids / isolation & purification
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Polymerase Chain Reaction
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Protein Isoforms / genetics
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Shiga Toxins / genetics*
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Shiga Toxins / isolation & purification
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Shiga-Toxigenic Escherichia coli / genetics*
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Shiga-Toxigenic Escherichia coli / isolation & purification
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Vegetables / microbiology
Substances
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DNA, Bacterial
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Escherichia coli Proteins
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MCR-1 protein, E coli
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Protein Isoforms
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Shiga Toxins
Grants and funding
This research work was supported by USDA-ARS CRIS 2030-42000-049-00D and 2030-42000-051-00D. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.