Microbiology Spectrum (Apr 2022)

Correlation between Identification of β-Lactamase Resistance Genes and Antimicrobial Susceptibility Profiles in Gram-Negative Bacteria: a Laboratory Data Analysis

  • Ammara Mushtaq,
  • Rachel Chasan,
  • Michael D. Nowak,
  • Meenakshi Rana,
  • Sahrish Ilyas,
  • Alberto E. Paniz-Mondolfi,
  • Emilia M. Sordillo,
  • Gopi Patel,
  • Melissa R. Gitman

DOI
https://doi.org/10.1128/spectrum.01485-21
Journal volume & issue
Vol. 10, no. 2

Abstract

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ABSTRACT We reported the frequency of resistance gene detection in Gram-negative blood culture isolates and correlated these findings with corresponding antibiograms. Data were obtained from 1045 isolates tested on the GenMark Dx ePlex Blood Culture Identification Gram-Negative Panels at the Mount Sinai Hospital Clinical Microbiology Laboratory in New York from March 2019 to February 2021. Susceptibilities were performed using Vitek 2 (bioMérieux Clinical Diagnostics) or Microscan (Beckman Coulter Inc.). blaCTX-M was detected in 26.4% Klebsiella pneumoniae, 23.5% Escherichia coli, and 16.4% Proteus mirabilis isolates. As would be expected, both blaCTX-M and blaCTX-M negative isolates were likely to be susceptible to newer agents while blaCTX-M positive isolates were more likely to be resistant to earlier generations of beta-lactam antibiotics. 3/204 blaCTX-M-positive isolates were found to be ceftriaxone-susceptible. Conversely, 2.8% ceftriaxone nonsusceptible strains were negative for all β-lactamase genes on the ePlex BCID-GN panel, including blaCTX-M. The prevalence of CTX-M-producing Enterobacterales remains high in the United States. A small number of blaCTX-M-positive isolates were susceptible to ceftriaxone, and a small number of ceftriaxone nonsusceptible isolates were negative for blaCTX-M. Further studies are needed to determine the optimal management when an isolate is phenotypically susceptible to ceftriaxone, but blaCTX-M is detected. IMPORTANCE There is limited literature on corresponding results obtained from rapid molecular diagnostics with the antibiotic susceptibility profile. We reported a correlation between the results obtained from ePlex and the antibiograms against a large collection of Gram-negative bacteria. We reported that there can be a discrepancy in a small number of cases, but the clinical significance of that is unknown.

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