Accuracy of Nanosphere Verigene Gram-Negative Blood Culture (BC-GN) Test for Rapid Detection of Extended-Spectrum Beta-Lactamases (ESBLs) From Positive Blood Cultures

Abstract

Abstract Background The rapid and accurate detection of ESBL production in Gram-negative rod (GNR) bacteremia is critical as recent data suggest that carbapenem treatment decreases mortality. At the same time, avoiding widespread empiric carbapenem prescribing is an important goal of antimicrobial stewardship teams. The aim of this retrospective review was to determine the accuracy of a nucleic acid–based test, Luminex Verigene BC-GN panel, to detect ESBL-positive GNRs direct from blood cultures. Methods The Verigene BC-GN was performed on all first positive GNR blood cultures. In addition, routine antibiotic susceptibility testing was performed on all isolates by the disk-diffusion method and included phenotypic ESBL testing using cefotaxime and ceftazidime with and without clavulanate. Escherichia coli, Klebsiella spp., and Proteus mirabilis–positive blood cultures were identified as ESBL producers through either Verigene or phenotypic disk testing. Positive GNR blood cultures from February 2016 to July 2017 were included for review. The primary objective was to determine the sensitivity and specificity of Verigene for detection of ESBLs. The secondary objective was assessing the percent of community-onset and hospital-acquired ESBL-positive blood cultures. Results There were 83 positive blood cultures with ESBL producing GNR included in the primary review. A total of 82 of 83 positive GNR blood cultures were CTX-M gene positive via Verigene (sensitivity 98.8%). All 83 cultures were confirmed as ESBL producers via phenotypic tests. There were no positive Verigene cases with negative phenotypic results. All 68 ESBL E coli–positive cultures were detected by Verigene (100%), 10 ESBL K pneumoniae (100%), and four of the five ESBL P mirabilis–positive cultures (80%). Of the 73 results available for review in the secondary objectives, 68 were community onset (93%) and five were hospital acquired (7%). Conclusion The majority of ESBL-positive blood cultures in a low-prevalence setting were due to CTX-M producers. The Luminex Verigene BC-GN was accurate in detecting ESBL-producing Enterobacteriaceae from blood cultures and can be reliably used to guide antimicrobial therapy.