Detection and epidemiology of carbapenemase producing Enterobacteriaceae in the Netherlands in 2013-2014

Laboratory detection of carbapenemase-producing Enterobacteriaceae (CPE) is complicated. Screening with MIC values below clinical breakpoints followed by genotypic confirmation is recommended. We evaluated the application of recommended CPE screening and confirmation methods and provide an overview of CPE epidemiology in E. coli and K. pneumoniae in the Netherlands. Data on E. coli and K. pneumoniae isolates with elevated meropenem (>0.25 mg/L) and/or imipenem (>1 mg/L) MIC values in 2013-2014 were selected from the Infectious Disease Surveillance Information System for Antibiotic Resistance. Laboratories were requested to provide additional results of any confirmatory testing performed. Confirmation of elevated carbapenem MIC values using gradient testing was performed in 59.8 % of eligible isolates. Confirmatory testing showed elevated MIC values in 8 % of E. coli and 32 % of K. pneumoniae isolates. The overall proportion of confirmed non-susceptible E. coli and K. pneumoniae was 0.01 % and 0.16 %, respectively. Genotypic confirmation was performed in 61.0 % of isolates with confirmed elevated carbapenem MIC values. A carbapenemase gene was identified in 47 % of E. coli and 65 % of K. pneumoniae isolates. OXA-48, NDM and KPC were the most frequently found carbapenemase genes. The majority (62 %) of CPE isolates was detected through targeted screening. CPE are a rare finding in the Netherlands. Adherence to the national guideline is suboptimal and differs between laboratories, implying a risk of inadequate CPE detection. Since accurate identification of CPE is the first step in prevention of CPE spread, successful implementation of guidelines for testing and reporting of CPE is essential.