title: Rapid detection ofcfiAmetallo-β-lactamase-producingBacteroides fragilisby the combination of MALDI-TOF MS and CarbaNP.
abstract: OBJECTIVE
  Carbapenem resistance inBacteroides fragilisis emerging and is mainly attributed to insertion sequence (IS)-mediated activation of the carbapenemase genecfiA. We investigated the use of matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and the CarbaNP assay for the rapid identification of these strains.
  
  
  METHODS
  This study used the Bruker MALDI Biotype system and the mass spectra models generated by 20B. fragilisreference strains (10cfiA-positive and 10cfiA-negative) in the ClinProTools software to identify 404B. fragilis(71cfiA-positive and 333cfiA-negative) clinical isolates. The ability of the CarbaNP assay to detect IS-mediated activation of thecfiAgene was assessed and the results obtained by molecular analysis were used as reference methods.
  
  
  RESULTS
  The support vector machine model generated by ClinProTools was found to be the most reliable algorithm for differentiation ofcfiA-positive andcfiA-negativeB. fragilissubgroups. Using the direct transfer method, all but onecfiA-negative isolates were correctly identified to the two subgroups by the model. The correct identification of thecfiA-negative isolate was obtained upon retesting by the extraction method. Of the 81cfiA-positive isolates, PCR and sequencing showed that 30 had an IS element providing the promoter for activation ofcfiA. With regard to the presence of the IS element, the CarbaNP test in thecfiAupstream region had 100% sensitivity, 80.4% specificity, 75.0% positive predictive value and 100% negative predictive value.
  
  
  CONCLUSIONS
  The combination of MALDI-TOF MS and the CarbaNP assay can be applied in diagnostic clinical laboratory for rapid identification ofB. fragiliswith IS element-activatedcfiAgene.
authors.affiliation: Department of Microbiology and Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
authors.forename: Pak-Leung
authors.identifier: http://orcid.org/0000-0002-8811-1308
authors.initials: PL
authors.lastname: Ho
authors.affiliation: Department of Microbiology and Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
authors.forename: Chong-Yee
authors.initials: CY
authors.lastname: Yau
authors.affiliation: Department of Clinical Pathology, Kwong Wah Hospital, Hospital Authority, Hong Kong, China.
authors.forename: Lok-Yan
authors.initials: LY
authors.lastname: Ho
authors.affiliation: Department of Microbiology and Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
authors.forename: Jonathan H K
authors.initials: JHK
authors.lastname: Chen
authors.affiliation: Department of Microbiology and Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
authors.forename: Eileen L Y
authors.initials: ELY
authors.lastname: Lai
authors.affiliation: Department of Microbiology and Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
authors.forename: Stephanie W U
authors.initials: SWU
authors.lastname: Lo
authors.affiliation: Department of Clinical Pathology, Kwong Wah Hospital, Hospital Authority, Hong Kong, China.
authors.forename: Cindy W S
authors.initials: CWS
authors.lastname: Tse
authors.affiliation: Department of Microbiology and Carol Yu Centre for Infection, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
authors.forename: Kin-Hung
authors.initials: KH
authors.lastname: Chow
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis*; D001431:Bacteriological Techniques; D001441:Bacteroides fragilis / Q000201:enzymology*; D004352:Drug Resistance, Microbial / Q000502:physiology; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D060388:Support Vector Machine; D001618:beta-Lactamases / Q000032:analysis*
chemical_list: D001426:Bacterial Proteins; D001618:beta-Lactamases; C063912:carbapenemase
keywords: ANAEROBES; ANTIBIOTICS; ANTIMICROBIAL RESISTANCE; INFECTIONS