title: Tolerance of Listeria monocytogenes to Quaternary Ammonium Sanitizers Is Mediated by a Novel Efflux Pump Encoded by emrE.
abstract: A novel genomic island (LGI1) was discovered in Listeria monocytogenes isolates responsible for the deadliest listeriosis outbreak in Canada, in 2008. To investigate the functional role of LGI1, the outbreak strain 08-5578 was exposed to food chain-relevant stresses, and the expression of 16 LGI1 genes was measured. LGI1 genes with putative efflux (L. monocytogenes emrE [emrELm]), regulatory (lmo1851), and adhesion (sel1) functions were deleted, and the mutants were exposed to acid (HCl), cold (4°C), salt (10 to 20% NaCl), and quaternary ammonium-based sanitizers (QACs). Deletion of lmo1851 had no effect on the L. monocytogenes stress response, and deletion of sel1 did not influence Caco-2 and HeLa cell adherence/invasion, whereas deletion of emrE resulted in increased susceptibility to QACs (P < 0.05) but had no effect on the MICs of gentamicin, chloramphenicol, ciprofloxacin, erythromycin, tetracycline, acriflavine, and triclosan. In the presence of the QAC benzalkonium chloride (BAC; 5 μg/ml), 14/16 LGI1 genes were induced, and lmo1861 (putative repressor gene) was constitutively expressed at 4 °C, 37 °C, and 52 °C and in the presence of UV exposure (0 to 30 min). Following 1 h of exposure to BAC (10 μg/ml), upregulation of emrE (49.6-fold), lmo1851 (2.3-fold), lmo1861 (82.4-fold), and sigB (4.1-fold) occurred. Reserpine visibly suppressed the growth of the ΔemrELm strain, indicating that QAC tolerance is due at least partially to efflux activity. These data suggest that a minimal function of LGI1 is to increase the tolerance of L. monocytogenes to QACs via emrELm. Since QACs are commonly used in the food industry, there is a concern that L. monocytogenes strains possessing emrE will have an increased ability to survive this stress and thus to persist in food processing environments.
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada jovana.kovacevic@ubc.ca.
authors.forename: Jovana
authors.initials: J
authors.lastname: Kovacevic
authors.affiliation: Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ziegler
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada Department of Food Hygiene and Consumer Health Protection, Wrocław University of Environmental and Life Sciences, Wrocław, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Wałecka-Zacharska
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada.
authors.forename: Aleisha
authors.initials: A
authors.lastname: Reimer
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada.
authors.forename: David D
authors.initials: DD
authors.lastname: Kitts
authors.affiliation: Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Gilmour
mesh_terms: D000167:Acriflavine / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D001548:Benzalkonium Compounds / Q000494:pharmacology; D018938:Caco-2 Cells; D002170:Canada / Q000453:epidemiology; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005511:Food Handling / Q000592:standards; D005525:Food-Processing Industry / Q000592:standards; D019450:Genes, MDR; D044404:Genomic Islands; D006367:HeLa Cells; D006801:Humans; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D008088:Listeriosis / Q000453:epidemiology / Q000382:microbiology / Q000517:prevention & control; D008826:Microbial Sensitivity Tests; D009154:Mutation; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D014260:Triclosan / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D001426:Bacterial Proteins; D001548:Benzalkonium Compounds; D000644:Quaternary Ammonium Compounds; D000167:Acriflavine; D014260:Triclosan