title: Molecular epidemiology and mechanisms of carbapenem resistance in Pseudomonas aeruginosa isolates from Spanish hospitals.
abstract: All (236) Pseudomonas aeruginosa isolates resistant to imipenem and/or meropenem collected during a multicenter (127-hospital) study in Spain were analyzed. Carbapenem-resistant isolates were found to be more frequently resistant to all beta-lactams and non-beta-lactam antibiotics than carbapenem-susceptible isolates (P < 0.001), and up to 46% of the carbapenem-resistant isolates met the criteria used to define multidrug resistance (MDR). Pulsed-field gel electrophoresis revealed remarkable clonal diversity (165 different clones were identified), and with few exceptions, the levels of intra- and interhospital dissemination of clones were found to be low. Carbapenem resistance was driven mainly by the mutational inactivation of OprD, accompanied or not by the hyperexpression of AmpC or MexAB-OprM. Class B carbapenemases (metallo-beta-lactamases [MBLs]) were detected in a single isolate, although interestingly, this isolate belonged to one of the few epidemic clones documented. The MBL-encoding gene (bla(VIM-2)), along with the aminoglycoside resistance determinants, was transferred to strain PAO1 by electroporation, demonstrating its plasmid location. The class 1 integron harboring bla(VIM-2) was characterized as well, and two interesting features were revealed: intI1 was found to be disrupted by a 1.1-kb insertion sequence, and a previously undescribed aminoglycoside acetyltransferase-encoding gene [designated aac(6')-32] preceded bla(VIM-2). AAC(6')-32 showed 80% identity to AAC(6')-Ib' and the recently described AAC(6')-31, and when aac(6')-32 was cloned into Escherichia coli, it conferred resistance to tobramycin and reduced susceptibility to gentamicin and amikacin. Despite the currently low prevalence of epidemic clones with MDR, active surveillance is needed to detect and prevent the dissemination of these clones, particularly those producing integron- and plasmid-encoded MBLs, given their additional capacity for the intra- and interspecies spread of MDR.
authors.affiliation: Servicio de Microbiología and Unidad de Investigación, Hospital Son Dureta, Instituto Universitario de Investigación en Ciencias de la Salud (IUNICS), Palma de Mallorca, Spain.
authors.forename: O
authors.initials: O
authors.lastname: Gutiérrez
authors.forename: C
authors.initials: C
authors.lastname: Juan
authors.forename: E
authors.initials: E
authors.lastname: Cercenado
authors.forename: F
authors.initials: F
authors.lastname: Navarro
authors.forename: E
authors.initials: E
authors.lastname: Bouza
authors.forename: P
authors.initials: P
authors.lastname: Coll
authors.forename: J L
authors.initials: JL
authors.lastname: Pérez
authors.forename: A
authors.initials: A
authors.lastname: Oliver
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D015780:Carbapenems / Q000494:pharmacology*; D002876:Chromosomes, Bacterial / Q000235:genetics; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D032023:Integrons / Q000235:genetics; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D018272:Porins / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013030:Spain / Q000453:epidemiology; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D004269:DNA, Bacterial; D018272:Porins; C077157:OprD protein, Pseudomonas aeruginosa; C048795:AmpC beta-lactamases; D001618:beta-Lactamases