title: Benzalkonium tolerance genes and outcome in Listeria monocytogenes meningitis.
abstract: OBJECTIVE
  Listeria monocytogenes is a food-borne pathogen that can cause meningitis. The listerial genotype ST6 has been linked to increasing rates of unfavourable outcome over time. We investigated listerial genetic variation and the relation with clinical outcome in meningitis.
  
  
  METHODS
  We sequenced 96 isolates from adults with listerial meningitis included in two prospective nationwide cohort studies by whole genome sequencing, and evaluated associations between bacterial genetic variation and clinical outcome. We validated these results by screening listerial genotypes of 445 cerebrospinal fluid and blood isolates from patients over a 30-year period from the Dutch national surveillance cohort.
  
  
  RESULTS
  We identified a bacteriophage, phiLMST6 co-occurring with a novel plasmid, pLMST6, in ST6 isolates to be associated with unfavourable outcome in patients (p 2.83e-05). The plasmid carries a benzalkonium chloride tolerance gene, emrC, conferring decreased susceptibility to disinfectants used in the food-processing industry. Isolates harbouring emrC were growth inhibited at higher levels of benzalkonium chloride (median 60 mg/L versus 15 mg/L; p <0.001), and had higher MICs for amoxicillin and gentamicin compared with isolates without emrC (both p <0.001). Transformation of pLMST6 into naive strains led to benzalkonium chloride tolerance and higher MICs for gentamicin.
  
  
  CONCLUSIONS
  These results show that a novel plasmid, carrying the efflux transporter emrC, is associated with increased incidence of ST6 listerial meningitis in the Netherlands. Suggesting increased disease severity, our findings warrant consideration of disinfectants used in the food-processing industry that select for resistance mechanisms and may, inadvertently, lead to increased risk of poor disease outcome.
authors.affiliation: Department of Neurology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: P H C
authors.initials: PH
authors.lastname: Kremer
authors.affiliation: Pathogen Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Lees
authors.affiliation: Department of Neurology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: M M
authors.initials: MM
authors.lastname: Koopmans
authors.affiliation: Department of Neurology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: B
authors.initials: B
authors.lastname: Ferwerda
authors.affiliation: Department of Medical Microbiology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands; Netherlands Reference Laboratory for Bacterial Meningitis, Academic Medical Centre/RIVM, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: A W M
authors.initials: AW
authors.lastname: Arends
authors.affiliation: Department of Medical Microbiology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands; Netherlands Reference Laboratory for Bacterial Meningitis, Academic Medical Centre/RIVM, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: M M
authors.initials: MM
authors.lastname: Feller
authors.affiliation: Department of Medical Microbiology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands; Netherlands Reference Laboratory for Bacterial Meningitis, Academic Medical Centre/RIVM, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Schipper
authors.affiliation: Department of Neurology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Valls Seron
authors.affiliation: Department of Medical Microbiology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands; Netherlands Reference Laboratory for Bacterial Meningitis, Academic Medical Centre/RIVM, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: van der Ende
authors.affiliation: Department of Neurology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: M C
authors.initials: MC
authors.lastname: Brouwer
authors.affiliation: Department of Neurology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: d.vandebeek@amc.uva.nl.
authors.forename: D
authors.initials: D
authors.lastname: van de Beek
authors.affiliation: Pathogen Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, UK. Electronic address: sdb@sanger.ac.uk.
authors.forename: S D
authors.initials: SD
authors.lastname: Bentley
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D015331:Cohort Studies; D024881:Drug Resistance, Bacterial; D005260:Female; D014644:Genetic Variation; D016680:Genome, Bacterial; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D008297:Male; D008584:Meningitis, Listeria / Q000382:microbiology* / Q000401:mortality*; D008875:Middle Aged; D009426:Netherlands; D063868:Patient Outcome Assessment; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D011159:Population Surveillance; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D001548:Benzalkonium Compounds
keywords: Bacterial genetics; Bacterial meningitis; Genome-wide association study; Listeria monocytogenes; Meningitis