Document Type
Article
Publication Date
9-2-2020
Publication Source
Journal of Global Antimicrobial Resistance
Abstract
Objectives: Many multidrug-resistant Gram-negative bacilli (MDR-GNB) harbour multiple β-lactamases. The aim of this study was to assess the impact of multiple β-lactamase carriage on the accuracy of susceptibility tests and extended-spectrum β-lactamase (ESBL) and carbapenemase confirmation methods.
Methods: A total of 50 MDR-GNB, of which 29 carried multiple β-lactamases, underwent broth microdilution (BMD) and disk diffusion (DD) testing as well as confirmation tests for ESBLs and carbapenemases. Whole-genome sequencing (WGS) was used for β-lactamase gene identification.
Results: Categorical agreement of BMD and DD testing results ranged from 86.5 to 97.7% for 10 β-lactam agents. BMD and DD algorithms for ESBL detection were highly variable; 6 of 8 positive strains carried an ESBL plus a carbapenemase or an AmpC enzyme, which may confound antimicrobial selection. The sensitivity and specificity of the modified carbapenem inactivation method (mCIM) were both 100%, whilst mCIM and EDTA-modified carbapenem inactivation method (eCIM) when used together to differentiate serine from metallo-β-lactamase carriage were both 96%. Xpert® Carba-R results (in vitro diagnostic test) were consistent with WGS results. Predicting phenotypic carbapenem resistance from WGS data overall showed 100% specificity but only 66.7% sensitivity for Enterobacterales isolates that were non-susceptible to imipenem and meropenem.
Conclusions: Multiple β-lactamases in MDR-GNB does not impact DD results, the utility of mCIM/eCIM tests, or Xpert Carba-R results. However, ESBL algorithms produced inconsistent results and predicting carbapenem resistance from WGS data was problematic in such strains.
Inclusive pages
87-93
ISBN/ISSN
Online ISSN: 2213-7173; Print ISSN: 2213-7165
Document Version
Published Version
Publisher
Elsevier
Volume
23
Peer Reviewed
yes
Keywords
Carbapenems; Susceptibility testing; ESBL; AmpC; mCIM
eCommons Citation
Tenover, Fred C.; dela Cruz, Caitlin M.; Dewell, Scott; Le, Victoria M.; and Tickler, Isabella A., "Does the Presence of Multiple β-Lactamases in Gram-Negative Bacilli Impact the Results of Antimicrobial Susceptibility Tests and Extended-Spectrum β-Lactamase and Carbapenemase Confirmation Methods?" (2020). Biology Faculty Publications. 365.
https://ecommons.udayton.edu/bio_fac_pub/365
Included in
Biology Commons, Biotechnology Commons, Cell Biology Commons, Genetics Commons, Microbiology Commons, Molecular Genetics Commons
Comments
This document is made available for download in compliance with the publisher’s open-access policy. Permission documentation is on file.