title: Low sensitivity of Listeria monocytogenes to quaternary ammonium compounds.
abstract: Ninety-seven epidemiologically unrelated strains of Listeria monocytogenes were investigated for their sensitivities to quaternary ammonium compounds (benzalkonium chloride and cetrimide). The MICs for seven serogroup 1/2 strains were high. Three came from the environment and four came from food; none were isolated from human or animal samples. All 97 strains carried the mdrL gene, which encodes a multidrug efflux pump, and the orfA gene, a putative transcriptional repressor of mdrL. The absence of plasmids in four of the seven resistant strains and the conservation of resistance after plasmid curing suggested that the resistance genes are not plasmid borne. Moreover, PCR amplification and Southern blot hybridization experiments failed to find genes phylogenetically related to the qacA and smr genes, encoding multidrug efflux systems previously described for the genus Staphylococcus. The high association between nontypeability by phages and the loss of sensitivity to quaternary ammonium compounds are suggestive of an intrinsic resistance due to modifications in the cell wall.
authors.affiliation: Laboratoire de Microbiologie, Faculté de Médecine de Tours, 37032 Tours Cedex, France. laurent.mereghetti@med.univ-tours.fr
authors.forename: L
authors.initials: L
authors.lastname: Mereghetti
authors.forename: R
authors.initials: R
authors.lastname: Quentin
authors.forename: N
authors.initials: N
authors.lastname: Marquet-Van Der Mee
authors.forename: A
authors.initials: A
authors.lastname: Audurier
mesh_terms: D017920:Antiporters / Q000235:genetics; D001426:Bacterial Proteins; D001434:Bacteriophage Typing; D001548:Benzalkonium Compounds / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics; D002593:Cetrimonium Compounds / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple / Q000235:genetics; D004783:Environmental Microbiology; D029968:Escherichia coli Proteins; D005516:Food Microbiology; D008089:Listeria monocytogenes / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; D001548:Benzalkonium Compounds; D002352:Carrier Proteins; D002593:Cetrimonium Compounds; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000644:Quaternary Ammonium Compounds; C068498:qacA protein, Staphylococcus aureus; C075436:EmrE protein, E coli