title: Mechanisms of carbapenem resistance in endemic Pseudomonas aeruginosa isolates after an SPM-1 metallo-β-lactamase producing strain subsided in an intensive care unit of a teaching hospital in Brazil.
abstract: Carbapenem-resistance mechanisms are a challenge in the treatment of Pseudomonas aeruginosa infections. We investigated changes in P. aeruginosa carbapenem-resistance determinants over a time period of eight years after the emergence of São Paulo metallo-β-lactamase in a university hospital in Rio de Janeiro, Brazil. Patients admitted to the intensive care unit (ICU) were screened for P. aeruginosa colonisation and followed for the occurrence of infections from April 2007 to April 2008. The ICU environment was also sampled. Isolates were typed using random amplified polymorphic DNA, pulsed-field gel electrophoresis and multilocus sequence typing. Antimicrobial susceptibility was determined by disk diffusion and E-test, production of carbapenemases by a modified-CarbaNP test and presence of carbapenemase-encoding genes by polymerase chain reaction. Non-carbapenemase resistance mechanisms studied included efflux and AmpC overexpression by PAβN and cloxacillin susceptibility enhancement, respectively, as well as oprD mutations. From 472 P. aeruginosa clinical isolates (93 patients) and 17 isolates from the ICU environment, high genotypic diversity and several international clones were observed; one environment isolate belonged to the blaSPM-1 P. aeruginosa epidemic genotype. Among isolates from infections, 10 (29%) were carbapenem resistant: none produced carbapenemases, three exhibited all non-carbapenemase mechanisms studied, six presented a combination of two mechanisms, and one exclusively displayed oprD mutations. Carbapenem-resistant P. aeruginosa displayed a polyclonal profile after the SPM-1 epidemic genotype declined. This phenomenon is connected with blaSPM-1 P. aeruginosa replaced by other carbapenem-resistant pathogens.
authors.affiliation: Universidade Federal do Rio de Janeiro, Faculdade de Medicina, Rio de Janeiro, RJ, Brasil.
authors.forename: Luciana Camila
authors.initials: LC
authors.lastname: Cacci
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Microbiologia, Rio de Janeiro, RJ, Brasil.
authors.forename: Stephanie Gomes
authors.initials: SG
authors.lastname: Chuster
authors.affiliation: Universidade Federal do Rio de Janeiro, Faculdade de Medicina, Rio de Janeiro, RJ, Brasil.
authors.forename: Natacha
authors.initials: N
authors.lastname: Martins
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Microbiologia, Rio de Janeiro, RJ, Brasil.
authors.forename: Pâmella Rodrigues do
authors.initials: PR
authors.lastname: Carmo
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Microbiologia, Rio de Janeiro, RJ, Brasil.
authors.forename: Valéria Brígido de Carvalho
authors.initials: VB
authors.lastname: Girão
authors.affiliation: Universidade Federal do Rio de Janeiro, Faculdade de Medicina, Rio de Janeiro, RJ, Brasil.
authors.forename: Simone Aranha
authors.initials: SA
authors.lastname: Nouér
authors.affiliation: Universidade Federal do Rio de Janeiro, Faculdade de Medicina, Rio de Janeiro, RJ, Brasil.
authors.forename: Wania Vasconcelos de
authors.initials: WV
authors.lastname: Freitas
authors.affiliation: Universidade Federal do Rio de Janeiro, Faculdade de Medicina, Rio de Janeiro, RJ, Brasil.
authors.forename: Juliana Arruda de
authors.initials: JA
authors.lastname: Matos
authors.affiliation: Universidade Federal do Rio de Janeiro, Faculdade de Medicina, Rio de Janeiro, RJ, Brasil.
authors.forename: Ana Cristina de Gouveia
authors.initials: AC
authors.lastname: Magalhães
authors.affiliation: Universidade Federal do Rio de Janeiro, Faculdade de Medicina, Rio de Janeiro, RJ, Brasil.
authors.forename: Adriana Lúcia Pires
authors.initials: AL
authors.lastname: Ferreira
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Microbiologia, Rio de Janeiro, RJ, Brasil.
authors.forename: Renata Cristina
authors.initials: RC
authors.lastname: Picão
authors.affiliation: Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, Instituto de Microbiologia, Rio de Janeiro, RJ, Brasil.
authors.forename: Beatriz Meurer
authors.initials: BM
authors.lastname: Moreira
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015780:Carbapenems / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D052978:Disk Diffusion Antimicrobial Tests; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D006785:Hospitals, University; D006801:Humans; D007362:Intensive Care Units; D058885:Multilocus Sequence Typing; D016133:Polymerase Chain Reaction; D011446:Prospective Studies; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D018440:beta-Lactam Resistance / Q000187:drug effects / Q000235:genetics*; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D004269:DNA, Bacterial; C476155:beta-lactamase SPM-1, Pseudomonas aeruginosa; D001618:beta-Lactamases