An upgraded version of carbapenem inactivation method to detect Bacteroides fragilis carbapenemase.

An increase of carbapenemase-producing Bacteroides fragilis infections is observed. To detect such a resistance in B. fragilis, several tests exist that are expensive or show poor sensitivity and specificity. Therefore, we upgraded the Anaerobic Carbapenem Inactivation Method (Ana-CIM) to easily screen for carbapenemase-producing B. fragilis. The presence of carbapenemase cfiA gene was identified in 50 B. fragilis isolates by PCR. We modified the Ana-CIM by (1) increasing the bacterial inoculum, and (2) measuring the differences in diameter between the negative control and the testing disc. We correctly classified the cfiA-negative and positive isolates and could define a cut-off of positivity at 2 mm. Our modified Ana-CIM allowed to correctly discriminate the 31 cfiA-positive with meropenem MICs ranging from 1 to > 32 µg/mL. We anticipate that our modified Ana-CIM could be used in most clinical laboratories to easily screen for carbapenemase-producing B. fragilis, even at low levels. Copyright © 2022 Elsevier Inc. All rights reserved.

Citation

Nathan Nicolau-Guillaumet, Anaëlle Muggeo, Sophie Moussalih, Christophe de Champs, Alain Lozniewski, Corentine Alauzet, Thomas Guillard. An upgraded version of carbapenem inactivation method to detect Bacteroides fragilis carbapenemase. Diagnostic microbiology and infectious disease. 2023 Feb;105(2):115857

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PMID: 36436310

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