title: The Listeria monocytogenes transposon Tn6188 provides increased tolerance to various quaternary ammonium compounds and ethidium bromide.
abstract: Tolerance of the foodborne pathogen Listeria monocytogenes to sublethal concentrations of disinfectants has been frequently reported. Particularly, quaternary ammonium compounds (QACs) such as benzalkonium chloride (BC) are often used in disinfectants and also as antiseptics in food industry and hospitals. Recently, we described Tn6188, a novel transposon in L. monocytogenes harbouring the transporter QacH, a molecular mechanism leading to increased tolerance to BC. In this study, we investigated the presence of Tn6188 within the genus Listeria spp. Our screening indicates that the distribution of Tn6188 may be limited to L. monocytogenes. We confirm that QacH is responsible for the observed increase in tolerance by complementation of a qacH deletion mutant and introducing qacH in a Tn6188 negative strain. We investigated the transporter's substrate spectrum by determining minimal inhibitory concentrations (MICs) and showed that QacH also confers higher tolerance towards other QACs and ethidium bromide (EtBr). This result was supported by increased expression of qacH in the presence of the various substrates as determined by quantitative reverse transcriptase PCR (qRT-PCR). In addition, we detected expression of a Tn6188 transposase gene and circular forms of Tn6188, suggesting activity and possible transfer of this transposon.
authors.affiliation: Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Vienna, Austria.
authors.forename: Anneliese
authors.initials: A
authors.lastname: Müller
authors.forename: Kathrin
authors.initials: K
authors.lastname: Rychli
authors.forename: Andreas
authors.initials: A
authors.lastname: Zaiser
authors.forename: Cornelia
authors.initials: C
authors.lastname: Wieser
authors.forename: Martin
authors.initials: M
authors.lastname: Wagner
authors.forename: Stephan
authors.initials: S
authors.lastname: Schmitz-Esser
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004251:DNA Transposable Elements; D004202:Disinfectants / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004996:Ethidium / Q000494:pharmacology*; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004202:Disinfectants; D000644:Quaternary Ammonium Compounds; D004996:Ethidium
keywords: benzalkonium chloride; complementation; transposase