Carbapenemase-Producing Enterobacterales Verification

Since 2009, the NRC has been located in the Department for Medical Microbiology at the Ruhr-University Bochum in Bochum, Germany. For German primary diagnostic laboratories, both clinical and private, it exclusively provides the free service for the verification and genotyping of suspected carbapenemase-producing isolates. These laboratories are requested, but not obliged, to send Enterobacterales isolates that fulfil specific criteria, for E. coli these are: elevated minimum inhibitory concentrations (MIC) for ertapenem (> 0.5 mg/L), meropenem or imipenem (> 2 mg/L) or decreased inhibition zone diameters of < 25 mm for ertapenem (10 µg) or < 25 mm for meropenem (10 µg) or imipenem (10 µg), largely following the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines [23 ]. Along with the sample, diagnostic laboratories are asked to provide basic epidemiological data by filling in a structured submission form in accordance with the German data protection law, including information on the patients’ sex, date of birth, inpatient or outpatient status, geographical location as based on first three numbers of the German five-digit postal code referring to the hospital or surgery where the isolate was sampled, isolate source, infection status and information on prior hospitalisation or stay abroad 6 months before detection.
Details on phenotypic and molecular methods used at the NRC for the identification of carbapenemases are described elsewhere [24 (link)]. In brief, a comprehensive range of phenotypic tests is used to detect Enterobacterales isolates suggestive of being carbapenemase-producing. Individual PCR amplifications of KPC-, VIM-, IMP-, NDM- and OXA-48-encoding genes followed by the sequencing of PCR amplicons are routinely used to confirm and identify the carbapenemase genes.