title: A two-centre evaluation of RAPIDEC® CARBA NP for carbapenemase detection in Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter spp.
abstract: OBJECTIVE
  We evaluated the RAPIDEC(®) CARBA NP assay (bioMérieux SA, Marcy-l'Étoile, France), a colorimetric test for rapid detection of carbapenemases, at two sites: Karolinska University Laboratory and PHE's national reference laboratory.
  
  
  METHODS
  A total of 138 bacterial isolates previously characterized as positive for class A, B and/or D carbapenemase genes and 138 supposed non-carbapenemase producers were tested with RAPIDEC(®) CARBA NP according to the manufacturer's protocol. Two carbapenemase-producing isolates carried both NDM and OXA-48-like genes. Molecular detection of the expected carbapenemase gene(s) was used as the gold standard, and was performed by conventional and real-time PCR in-house assays.
  
  
  RESULTS
  The RAPIDEC(®) CARBA NP assay detected 135 of 138 carbapenemase producers; one OXA-48-producing Klebsiella pneumoniae and two Acinetobacter baumannii producing OXA-23 or OXA-24 were not detected. Among 'negative' controls, 135 of 138 isolates were negative by RAPIDEC(®) CARBA NP. The exceptions were one Klebsiella oxytoca, which was later found to produce GES-5 carbapenemase, one Pseudomonas aeruginosa with OprD loss and increased efflux, and one Enterobacter cloacae with impermeability. When numbers were adjusted for the GES-5 producer, the overall sensitivity of the RAPIDEC(®) CARBA NP test was 97.8% and its specificity was 98.5%.
  
  
  CONCLUSIONS
  The assay took less than 2.5 h to carry out, was user-friendly and had a high overall performance, making it an attractive option for clinical laboratories.
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Muhammad Humaun
authors.initials: MH
authors.lastname: Kabir
authors.affiliation: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, 61 Colindale Avenue, London NW9 5EQ, UK.
authors.forename: Daniele
authors.initials: D
authors.lastname: Meunier
authors.affiliation: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, 61 Colindale Avenue, London NW9 5EQ, UK.
authors.forename: Katie L
authors.initials: KL
authors.lastname: Hopkins
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden christian.giske@karolinska.se.
authors.forename: Christian G
authors.initials: CG
authors.lastname: Giske
authors.affiliation: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, 61 Colindale Avenue, London NW9 5EQ, UK.
authors.forename: Neil
authors.initials: N
authors.lastname: Woodford
mesh_terms: D040981:Acinetobacter baumannii / Q000201:enzymology*; D001426:Bacterial Proteins / Q000032:analysis*; D001431:Bacteriological Techniques / Q000379:methods*; D003124:Colorimetry / Q000379:methods*; D004755:Enterobacteriaceae / Q000201:enzymology*; D006801:Humans; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D012680:Sensitivity and Specificity; D013997:Time Factors; D001618:beta-Lactamases / Q000032:analysis*
chemical_list: D001426:Bacterial Proteins; D001618:beta-Lactamases; C063912:carbapenemase