title: Comparison of phenotypic tests for the detection of metallo-beta-lactamases in clinical isolates of Pseudomonas aeruginosa.
abstract: Metallo-β-lactamase (MBL)-producing gram-negative bacteria are an increasing public health concern worldwide. Screening tests for the rapid and specific identification of these pathogens are essential, and should be included among routine diagnostics in laboratories. This study aimed to determine the MBL frequency among carbapenem-resistant Pseudomonas aeruginosa isolates, and to evaluate the accuracy of different tests in screening for MBL production. From January 2001 to December 2008, a total of 142 imipenem-non-susceptible P. aeruginosa strains were isolated from distinct clinical samples from hospitalized patients. These isolates were examined by PCR, MBL E-test, double-disk synergy test (DDST), and combined disk (CD) test. The minimal inhibitory concentration (MIC; μg/mL) was determined by agar dilution, and pulsed field gel electrophoresis (PFGE) was performed on all samples. Sequencing was performed to confirm and define the MBL variant and subtype. Using PCR and DNA sequence analysis, 93 strains were confirmed positive for MBLs, 91 strains for the blaSPM-1 gene, 1 strain for the blaIMP-1 gene, and 1 strain for the blaIMP-16 gene. PFGE displayed a clonal pattern. The sensitivities, specificities, positive and negative predictive values were evaluated for all tests. The DDST assay (CAZ-MPA) was the optimal method for screening MBL production in P. aeruginosa strains. However, the results of the CD assay (IMP/EDTA) showed close agreement with those of the DDST. In addition, the CD assay allowed a more objective interpretation and did not require the use of a toxic substance.
authors.affiliation: Post-Graduate Program in Internal Medicine and Health Sciences, Universidade Federal do Paraná, Curitiba, Brazil.
authors.forename: Andréa
authors.initials: A
authors.lastname: Lucena
authors.affiliation: Bacteriology Laboratory, Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, Brazil; Faculdades e Instituto de Pesquisa Pelé Pequeno Príncipe, Curitiba, Paraná, Brazil.
authors.forename: Libera M
authors.initials: LM
authors.lastname: Dalla Costa
authors.affiliation: Bacteriology Laboratory, Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, Brazil.
authors.forename: Keite da Silva
authors.initials: Kda S
authors.lastname: Nogueira
authors.affiliation: Laboratório Alerta, Universidade Federal de São Paulo, Brazil.
authors.forename: Adriana P
authors.initials: AP
authors.lastname: Matos
authors.affiliation: Laboratório Alerta, Universidade Federal de São Paulo, Brazil; Laboratório Especial de Microbiologia Clínica, Division of Infectious Diseases, Universidade Federal de São Paulo, Brazil.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Gales
authors.affiliation: Post-Graduate Program in Internal Medicine and Health Sciences, Universidade Federal do Paraná, Curitiba, Brazil. Electronic address: sraboni@ufpr.br.
authors.forename: Sonia M
authors.initials: SM
authors.lastname: Raboni
mesh_terms: D006801:Humans; D010641:Phenotype; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification; D001618:beta-Lactamases / Q000235:genetics* / Q000302:isolation & purification*
chemical_list: C409201:beta-lactamase IMP-1; D001618:beta-Lactamases
keywords: Metallo-beta-lactamase; Metalo-beta-lactamasa; Pruebas de detección; Pseudomonas aeruginosa; Screening test