Evaluation of a new meropenem–EDTA double-ended Etest strip for the detection of the CfiA metallo-β-lactamase in clinical isolates of Bacteroides fragilis

ABSTRACTThirty-five Bacteroides fragilis clinical isolates with varying susceptibility to meropenem were analysed with a prototype of a double-ended Etest strip containing meropenem ± EDTA, designed for the detection of the CfiA metallo-β-lactamase. Phenotypic results obtained with this new Etest strip were related to the genotype and compared to the results of the Etest containing imipenem ± EDTA. Whereas the Etest with imipenem ± EDTA only allowed detection of isolates with high-level resistance (both MICs of imipenem and meropenem >32 mg/L), reflecting the possible underestimation of CfiA prevalence in B. fragilis, the Etest with meropenem ± EDTA proved to be more accurate, particularly for isolates with low-level carbapenem resistance, suggesting its potential for broader detection of CfiA production.