Evaluation of the French novel disc diffusion-based algorithm for the phenotypic screening of carbapenemase-producing Enterobacterales

Abstract

ObjectivesThe early identification of carbapenemase-producing Enterobacterales (CPE) is required to prevent their spread and initiate proper therapy. Accordingly, it is crucial to develop efficient algorithms using susceptibility testing results to discriminate non-carbapenemase producers (non-CPE) from those that require complementary tests. In 2022, to adapt its recommendations to the evolution of CPE epidemiology (increased prevalence of OXA-244 producers), the Antibiogram Committee of the French Society of Microbiology (CA-SFM) proposed a new algorithm for the screening of CPE. We compared this algorithm to the former algorithm (2015-2021). MethodsFrom July 2022 to January 2023, all nonduplicate enterobacterial isolates referred to French National Reference Centre for carbapenemase detection (n = 518) were subjected to the former CA-SFM algorithm (2015 to 2021) using inhibition diameters of ertapenem, ticarcillin-clavulanate, temocillin and meropenem or imipenem, and the novel CA-SFM algorithm (since 2022) using inhibition diameters of ceftazidime-avibactam, temocillin, and meropenem or imipenem. ResultsSensitivity, specificity, negative predictive value, and positive predictive value were of 80.8% (CI95 76.3%–84.6%), 66.2% (58.1%–73.5%), 59.3% (51.5%–66.6%), and 85.0% (80.7% - 88.5%) for the old CA-SFM algorithm and 97.8% (95.5%–99.0%), 45.5% (37.5%–53.7%), 89.7% (80.3%–95.2%), and 80.9% (76.9%–84.4%) for the novel CA-SFM algorithm. DiscussionThe novel CA-SFM algorithm possesses the best performance for the screening of CPE particularly in countries with a high prevalence of OXA-48-like producers.