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Published on: August 8, 2016
Prospective evaluation of an algorithm for the phenotypic screening of carbapenemase-producing Enterobacteriaceae
Laurent Dortet1, Gaelle Cuzon2, Patrick Plésiat3
1Bacteriology-Hygiene Unit, Assistance Publique/Hôpitaux de Paris, Bicêtre Hospital, Le Kremlin-Bicêtre, France French National Reference Centre for Antibiotic Resistance: Carbapenemase-Producing Enterobacteriaceae, Le Kremlin-Bicêtre, France EA7361 Research Unit 'Structure, dynamic, function and expression of broad spectrum β-lactamases', Paris-Sud University, LabEx LERMIT, Faculty of Medicine, Le Kremlin-Bicêtre, France laurent.dortet@bct.aphp.fr.
Objectives:
The objective of this study was to assess the performance of an algorithm based on the disc diffusion method for the screening of carbapenemase-producing Enterobacteriaceae (CPE) referred to the French National Reference Centre for Antibiotic Resistance.
Methods:
From April to June 2014, all isolates of Enterobacteriaceae referred to the French National Reference Centre for Antibiotic Resistance were included. The inhibition zone diameters of imipenem, ticarcillin/clavulanate and temocillin using EUCAST disc diffusion methodology were recorded. All isolates were subjected to the algorithm proposed by the Antibiogram Committee of the French Society of Microbiology (CA-SFM) for the screening of carbapenemase producers. Phenotypic, biochemical and molecular detection of carbapenemases was performed for all isolates.
Results:
A total of 621 consecutive enterobacterial isolates with decreased susceptibility to carbapenems were tested. They included 213 CPE [OXA-48-like (n = 183), NDM (n = 22), VIM (n = 3), KPC (n = 3) and OXA-48-like + NDM (n = 2)] and 408 non-carbapenemase producers. The CA-SFM algorithm combining cut-off values of 15 mm, 15 mm and 22 mm for ticarcillin/clavulanate, temocillin and imipenem, respectively, perfectly detected 204 isolates (32.8%) as non-carbapenemase producers, leading to a negative predictive value of 100% for this algorithm.
Conclusions:
Implementation of the CA-SFM algorithm in clinical microbiology laboratories may avoid additional testing for CPE in one-third of the enterobacterial isolates with decreased susceptibility to carbapenems.
