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

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.). was detected in 26.4% Klebsiella pneumoniae, 23.5% Escherichia coli, and 16.4% Proteus mirabilis isolates. As would be expected, both and negative isolates were likely to be susceptible to newer agents while positive isolates were more likely to be resistant to earlier generations of beta-lactam antibiotics. 3/204 -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 . The prevalence of CTX-M-producing Enterobacterales remains high in the United States. A small number of -positive isolates were susceptible to ceftriaxone, and a small number of ceftriaxone nonsusceptible isolates were negative for . Further studies are needed to determine the optimal management when an isolate is phenotypically susceptible to ceftriaxone, but is detected. 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.