title: Emergence of extensive-drug-resistant Pseudomonas aeruginosa in a French university hospital.
abstract: The aim of this study was to describe the molecular epidemiology and the mechanisms of resistance to beta-lactams of emerging extensive-drug-resistant Pseudomonas aeruginosa (XDRPA) in a tertiary-care university hospital over a three-year period. Analysis included antimicrobial susceptibility profiling and pulsed-field gel electrophoresis (PFGE). Resistance mechanisms to beta-lactams were identified: production of naturally occurring and acquired beta-lactamases, overproduction of MexAB-OprM and MexXY efflux systems and loss of porin OprD were assessed. Eighteen patients were colonised or infected with XDRPA which remained susceptible to colistin and, to a lesser extent, to rifampicin. beta-lactam resistance was, in most cases, due to the overproduction of AmpC, overproduction of the MexXY efflux system and loss of porin OprD. One isolate produced the class D extended-spectrum oxacillinase (OXA-ESBL) Oxa-28, but none produced metallo-beta-lactamase (MBL) or class A extended-spectrum beta-lactamase (ESBL). The XDRPA clustered in eight PFGE patterns and both the acquisition and loss of resistance determinants was observed within a single clone during its spread. The emergence of XDRPA isolates in our university hospital has been characterised by genotypic heterogeneity, variation of mechanisms of resistance to beta-lactams in a single clone and the predominance of chromosomally encoded resistance mechanisms.
authors.affiliation: Service de Bactériologie, Centre Hospitalier Universitaire Besançon, Besançon, France.
authors.forename: L
authors.initials: L
authors.lastname: Vettoretti
authors.forename: N
authors.initials: N
authors.lastname: Floret
authors.forename: D
authors.initials: D
authors.lastname: Hocquet
authors.forename: B
authors.initials: B
authors.lastname: Dehecq
authors.forename: P
authors.initials: P
authors.lastname: Plésiat
authors.forename: D
authors.initials: D
authors.lastname: Talon
authors.forename: X
authors.initials: X
authors.lastname: Bertrand
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016000:Cluster Analysis; D021821:Communicable Diseases, Emerging / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D003428:Cross Infection / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D004305:Dose-Response Relationship, Drug; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005602:France / Q000453:epidemiology; D005838:Genotype; D006785:Hospitals, University; D006801:Humans; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D011552:Pseudomonas Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018440:beta-Lactam Resistance / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents