Comprehensive evaluation of the MBT STAR-BL module for simultaneous bacterial identification and β-lactamase-mediated resistance detection in Gram-negative rods from cultured isolates and positive blood cultures

Annie W.T. Lee, Johnson K.S. Lam, Ricky K.W. Lam, Wan H. Ng, Ella N.L. Lee, Vicky T.Y. Lee, Po P. Sze, Rahim Rajwani, Kitty S.C. Fung, Wing K. To, Rodney A. Lee, Dominic N.C. Tsang, Kit Hang Siu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

9 Citations (Scopus)

Abstract

Objective: This study evaluated the capability of a MALDI Biotyper system equipped with the newly introduced MBT STAR-BL module to simultaneously perform species identification and β-lactamase-mediated resistance detection in bacteremia -causing bacteria isolated from cultured isolates and patient-derived blood cultures (BCs). Methods: Two hundred retrospective cultured isolates and 153 prospective BCs containing Gram-negative rods (GNR) were collected and subjected to direct bacterial identification, followed by the measurement of β-lactamase activities against ampicillin, piperacillin, cefotaxime, ceftazidime, and meropenem using the MBT STAR-BL module. The results and turnaround times were compared with those of routine microbiological processing. All strains were also characterized by beta-lactamase PCR and sequencing. Results: Using the saponin-based extraction method, MALDI-TOF MS correctly identified bacteria in 116/134 (86.6%) monomicrobial BCs. The detection sensitivities for β-lactamase activities against ampicillin, piperacillin, third-generation cephalosporin and meropenem were 91.3, 100, 97.9, and 100% for cultured isolates, and 80.4, 100, 68.8, and 40% for monomicrobial BCs (n = 134) respectively. The overall specificities ranged from 91.5 to 100%. Furthermore, the MBT STAR-BL and conventional drug susceptibility test results were concordant in 14/19 (73.7%) polymicrobial cultures. Reducing the logRQ cut-offvalue from 0.4 to 0.2 increased the direct detection sensitivities for β-lactamase activities against ampicillin, cefotaxime and meropenem in BCs to 85.7, 87.5, and 100% respectively. The MBT STAR-BL test enabled the reporting of β-lactamase-producing GNR at 14.16 and 47.64 h before the interim and final reports of routine BCs processing, respectively, were available. Conclusion: The MALDI Biotyper system equipped with the MBT STAR-BL module enables the simultaneous rapid identification of bacterial species and β-lactamase-mediated resistance from BCs and cultured isolates. Adjustment of the logRQ cut-offvalue to 0.2 significantly increased the detection sensitivities for clinically important drug-resistant pathogens.
Original languageEnglish
Article number334
JournalFrontiers in Microbiology
Volume9
Issue numberFEB
DOIs
Publication statusPublished - 23 Feb 2018

Keywords

  • Bacterial
  • Beta-lactamases
  • Blood culture
  • Drug hydrolysis test
  • Drug resistance
  • MALDI-TOF MS
  • MBT STAR-BL

ASJC Scopus subject areas

  • Microbiology
  • Microbiology (medical)

Cite this