title: Evaluation of several phenotypic methods for the detection of carbapenemase-producing Pseudomonas aeruginosa.
abstract: The purpose of this investigation was to compare several phenotypic methods, including combined disk tests (CDT) containing metallo-β-lactamase (MBL) inhibitors or cloxacillin, and the Carba NP test for the detection of carbapenemase-producing Pseudomonas aeruginosa (CPPA). A new CDT using imipenem (10 μg) ± cloxacillin 4,000 μg and the Carba NP test were evaluated to detect CPPA. In addition, four commercially available combined disks containing a carbapenem and ethylene-diamine-tetra-acetic acid (EDTA) or dipicolinic acid (DPA) as the inhibitor were tested in order to detect MBL-positive P. aeruginosa. All these phenotypic methods were evaluated on 188 imipenem non-susceptible P. aeruginosa (CPPA, n = 75) isolates divided into 26 well-characterized collection strains and 162 non-duplicate clinical isolates referred to the national reference laboratory in 2013. For the total of 188 isolates tested, CDT containing EDTA or DPA displayed high sensitivities (99%) and specificities (95%) for detecting MBL-producing isolates. CDT with cloxacillin showed a sensitivity and specificity of 97%/96% compared to 88%/99% for the Carba NP test in order to detect CPPA. For the 162 clinical isolates, CDT containing EDTA or DPA displayed a high negative predictive value (NPV) (99%) for detecting MBL-producing isolates. CDT with cloxacillin showed an NPV of 98%, compared to 95% for the Carba NP test in order to detect CPPA. In our setting, CDT associating imipenem ± EDTA or ± DPA performed best for the detection of MBL-producing P. aeruginosa. Imipenem/imipenem-cloxacillin test yielded good NPV to exclude the presence of MBL in imipenem non-susceptible isolates.
authors.affiliation: National Reference Laboratory for Monitoring of Antimicrobial Resistance in Gram-Negative Bacteria, CHU Dinant Godinne, Université catholique de Louvain (UCL), Yvoir, Belgium, amelie.heinrichs@ulb.ac.be.
authors.forename: A
authors.initials: A
authors.lastname: Heinrichs
authors.forename: T D
authors.initials: TD
authors.lastname: Huang
authors.forename: C
authors.initials: C
authors.lastname: Berhin
authors.forename: P
authors.initials: P
authors.lastname: Bogaerts
authors.forename: Y
authors.initials: Y
authors.lastname: Glupczynski
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D004789:Enzyme Activation; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D010641:Phenotype; D011552:Pseudomonas Infections / Q000175:diagnosis* / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001618:beta-Lactamases; C063912:carbapenemase