title: Cloning, nucleotide sequencing, and analysis of the AcrAB-TolC efflux pump of Enterobacter cloacae and determination of its involvement in antibiotic resistance in a clinical isolate.
abstract: Enterobacter cloacae is an emerging clinical pathogen that may be responsible for nosocomial infections. Management of these infections is often difficult, owing to the high frequency of strains that are resistant to disinfectants and antimicrobial agents in the clinical setting. Multidrug efflux pumps, especially those belonging to the resistance-nodulation-division family, play a major role as a mechanism of antimicrobial resistance in gram-negative pathogens. In the present study, we cloned and sequenced the genes encoding an AcrAcB-TolC-like efflux pump from an E. cloacae clinical isolate (isolate EcDC64) showing a broad antibiotic resistance profile. Sequence analysis showed that the acrR, acrA, acrB, and tolC genes encode proteins that display 79.8%, 84%, 88%, and 82% amino acid identities with the respective homologues of Enterobacter aerogenes and are arranged in a similar pattern. Deletion of the acrA gene to yield an AcrA-deficient EcDC64 mutant (EcDeltaacrA) showed the involvement of AcrAB-TolC in multidrug resistance in E. cloacae. However, experiments with an efflux pump inhibitor suggested that additional efflux systems also play a role in antibiotic resistance. Investigation of several unrelated isolates of E. cloacae by PCR analysis revealed that the AcrAB system is apparently ubiquitous in this species.
authors.affiliation: Servicio de Microbiología-Unidad de Investigación, Complejo Hospitalario Universitario Juan Canalejo, 15006 La Coruña, Spain.
authors.forename: Astrid
authors.initials: A
authors.lastname: Pérez
authors.forename: Delia
authors.initials: D
authors.lastname: Canle
authors.forename: Cristina
authors.initials: C
authors.lastname: Latasa
authors.forename: Margarita
authors.initials: M
authors.lastname: Poza
authors.forename: Alejandro
authors.initials: A
authors.lastname: Beceiro
authors.forename: María del Mar
authors.initials: Mdel M
authors.lastname: Tomás
authors.forename: Ana
authors.initials: A
authors.lastname: Fernández
authors.forename: Susana
authors.initials: S
authors.lastname: Mallo
authors.forename: Sonia
authors.initials: S
authors.lastname: Pérez
authors.forename: Francisca
authors.initials: F
authors.lastname: Molina
authors.forename: Rosa
authors.initials: R
authors.lastname: Villanueva
authors.forename: Iñigo
authors.initials: I
authors.lastname: Lasa
authors.forename: Germán
authors.initials: G
authors.lastname: Bou
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016972:Enterobacter cloacae / Q000187:drug effects / Q000235:genetics*; D004756:Enterobacteriaceae Infections / Q000382:microbiology*; D019450:Genes, MDR / Q000235:genetics; D005822:Genetic Vectors; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D018272:Porins / Q000235:genetics; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: C493251:AcrAB-TolC protein, Salmonella enterica; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; C113724:OmpC protein; D018272:Porins; C048795:AmpC beta-lactamases; D001618:beta-Lactamases