title: Differential contribution of AcrAB and OqxAB efflux pumps to multidrug resistance and virulence in Klebsiella pneumoniae.
abstract: OBJECTIVE
  In Klebsiella pneumoniae, overexpression of the AcrAB efflux pump and the more recently described OqxAB efflux pump has been linked to an antibiotic cross-resistance phenotype, but the mechanisms of regulation are largely unknown. Moreover, while AcrAB has been shown to participate in K. pneumoniae virulence, the contribution of OqxAB has not yet been assessed.
  
  
  METHODS
  In the present study we investigated a K. pneumoniae clinical isolate (KPBj1 E+), displaying cross-resistance to quinolones, chloramphenicol and cefoxitin, and its phenotypic revertant (KPBj1 Rev, susceptible to antibiotics) by using whole-genome sequencing, RT-PCR, complementation and a Caenorhabditis elegans virulence model.
  
  
  RESULTS
  We detected a point mutation in the oqxR repressor gene of KPBj1 E+, which overexpressed genes rarA, encoding a transcriptional regulator, and oqxB, but not acrB. Complementation with wild-type oqxR restored antibiotic susceptibility and normalized rarA and oqxB expression levels. Whole-genome sequencing showed that KPBj1 Rev had lost the entire rarA-oqxABR locus, situated close to an integration hot spot of phage P4. This large deletion seemed responsible for the significantly lower virulence potential of strain KPBj1 Rev compared with KPBj1 E+. Moreover, we found that KPBj1 E+ ΔacrB was significantly less virulent than its parental strain.
  
  
  CONCLUSIONS
  This work demonstrates the role of the overexpression of efflux pump OqxAB, due to a mutation in gene oqxR, in the antibiotic resistance phenotype of a clinical isolate, and suggests that the presence of AcrAB, associated with overexpression of OqxAB, is required for high virulence potential.
authors.affiliation: Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France Institut Pasteur, Microbial Evolutionary Genomics, Paris, France CNRS, UMR3525, Paris, France.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Bialek-Davenet
authors.affiliation: INSERM U1047, Université Montpellier 1, UFR de Médecine, Nîmes, France Laboratoire de Bactériologie, CHU Caremeau, Nîmes, France.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Lavigne
authors.affiliation: Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France Faculté de Médecine Paris Diderot, Paris, France.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Guyot
authors.affiliation: Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France.
authors.forename: Noémie
authors.initials: N
authors.lastname: Mayer
authors.affiliation: Institut Pasteur, Pathogénie Microbienne Moléculaire, Paris, France INSERM U786, Paris, France.
authors.forename: Régis
authors.initials: R
authors.lastname: Tournebize
authors.affiliation: Institut Pasteur, Microbial Evolutionary Genomics, Paris, France CNRS, UMR3525, Paris, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Brisse
authors.affiliation: Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Leflon-Guibout
authors.affiliation: Service de Microbiologie, Hôpital Beaujon, AP-HP, Clichy, France Faculté de Médecine Paris Diderot, Paris, France INSERM UMR 1149, Université Paris 7, Paris, France mhn.chanoine@bjn.aphp.fr.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Nicolas-Chanoine
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001693:Biological Transport, Active; D017173:Caenorhabditis elegans; D004195:Disease Models, Animal; D024901:Drug Resistance, Multiple, Bacterial; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007710:Klebsiella Infections / Q000382:microbiology* / Q000473:pathology; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D026901:Membrane Transport Proteins; D037521:Virulence Factors
keywords: K. pneumoniae; antimicrobial resistance; efflux systems