title: Comparative Phenotypic and Genotypic Analysis of Swiss and FinnishListeria monocytogenesIsolates with Respect to Benzalkonium Chloride Resistance.
abstract: Reduced susceptibility ofListeria monocytogenesto benzalkonium chloride (BC), a quaternary ammonium compound widely used in food processing and hospital environments, is a growing public health and food safety concern. The minimal inhibitory concentration of BC on 392L. monocytogenesstrains from Switzerland (CH) and Finland (FIN) was determined. Within this strain collection, benzalkonium chloride resistance was observed in 12.3% (24/195) of Swiss and 10.6% (21/197) of Finnish strains. In both countries, the highest prevalence of BC-resistant strains (CH: 29.4%; FIN: 38.9%) was detected among serotype 1/2c strains. Based on PCR analysis, genes coding for theqacHefflux pump system were detected for most of the BC-resistant strains (CH: 62.5%; FIN: 52.4%). Some Swiss BC-resistant strains harbored genes coding for thebcrABC(16.7%) efflux pump system, while one Finnish BC-resistant strain harbored theemrEgene previously only described among BC-resistantL. monocytogenesstrains from Canada. Interestingly, a subset of BC-resistant strains (CH: 5/24, 20.8%; FIN: 9/21, 42.8%) lacked genes for efflux pumps currently known to confer BC resistance inL. monocytogenes. BC resistance analysis in presence of reserpine showed that the resistance was completely or partially efflux pump dependent in 10 out of the 14 strains lacking the known BC resistance genes. Sequence types 155 and ST403 were over-representated among these strains suggesting that these strains might share similar but yet unknown mechanisms of BC resistance.
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich Zurich, Switzerland.
authors.forename: Anja B
authors.initials: AB
authors.lastname: Meier
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich Zurich, Switzerland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Guldimann
authors.affiliation: Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki Helsinki, Finland.
authors.forename: Annukka
authors.initials: A
authors.lastname: Markkula
authors.affiliation: Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki Helsinki, Finland.
authors.forename: Anna
authors.initials: A
authors.lastname: Pöntinen
authors.affiliation: Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki Helsinki, Finland.
authors.forename: Hannu
authors.initials: H
authors.lastname: Korkeala
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich Zurich, Switzerland.
authors.forename: Taurai
authors.initials: T
authors.lastname: Tasara
keywords: Listeria monocytogenes; MLST; bcrABC; benzalkonium chloride; emrE; qacH