title: Amino Acid Substitutions Account for Most MexS Alterations in Clinical nfxC Mutants of Pseudomonas aeruginosa.
abstract: Multidrug-resistant mutants ofPseudomonas aeruginosathat overproduce the active efflux system MexEF-OprN (callednfxCmutants) have rarely been characterized in the hospital setting. Screening of 221 clinical strains exhibiting a reduced susceptibility to ciprofloxacin (a substrate of MexEF-OprN) and imipenem (a substrate of the negatively coregulated porin OprD) led to the identification of 43 (19.5%)nfxCmutants. Subsequent analysis of 22 nonredundant mutants showed that, in contrast to theirin vitro-selected counterparts, only 3 of them (13.6%) harbored a disruptedmexSgene, which codes for the oxidoreductase MexS, whose inactivation is known to activate themexEF-oprNoperon through a LysR-type regulator, MexT. Nine (40.9%) of the clinicalnfxCmutants contained single amino acid mutations in MexS, and these were associated with moderate effects on resistance and virulence factor production in 8/9 strains. Finally, the remaining 10 (45.5%)nfxCmutants did not display mutations in any of the regulators known to controlmexEF-oprNexpression (themexS,mexT,mvaT, andampRgenes), confirming that other loci are responsible for pump upregulation in patients. Collectively, these data demonstrate thatnfxCmutants are probably more frequent in the hospital than previously thought and have genetic and phenotypic features somewhat different from those ofin vitro-selected mutants.
authors.affiliation: Laboratoire de Bactériologie EA4266, Faculté de Médecine-Pharmacie, Université de Franche-Comté, Besançon, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Richardot
authors.affiliation: Laboratoire de Bactériologie EA4266, Faculté de Médecine-Pharmacie, Université de Franche-Comté, Besançon, France.
authors.forename: Paulo
authors.initials: P
authors.lastname: Juarez
authors.affiliation: Laboratoire de Bactériologie EA4266, Faculté de Médecine-Pharmacie, Université de Franche-Comté, Besançon, France Laboratoire de Bactériologie, Centre Hospitalier Universitaire de Besançon, Besançon, France.
authors.forename: Katy
authors.initials: K
authors.lastname: Jeannot
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire de Besançon, Besançon, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Patry
authors.affiliation: Laboratoire de Bactériologie EA4266, Faculté de Médecine-Pharmacie, Université de Franche-Comté, Besançon, France Laboratoire de Bactériologie, Centre Hospitalier Universitaire de Besançon, Besançon, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Plésiat
authors.affiliation: Laboratoire de Bactériologie EA4266, Faculté de Médecine-Pharmacie, Université de Franche-Comté, Besançon, France cllanesb@univ-fcomte.fr.
authors.forename: Catherine
authors.initials: C
authors.lastname: Llanes
mesh_terms: D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002939:Ciprofloxacin / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009876:Operon; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C402791:MexXY protein, Pseudomonas aeruginosa; C105708:OprN protein, Pseudomonas aeruginosa; D037521:Virulence Factors; D002939:Ciprofloxacin; D015378:Imipenem
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