Incidence rates of carbapenemase-producing Enterobacteriaceae clinical isolates in France: a prospective nationwide study in 2011-12

Objectives: To determine proportions and incidence rates of Enterobacteriaceae producing carbapenemase among those non-susceptible (NS) to carbapenems in France.

Methods: From November 2011 to April 2012, 71 laboratories recorded non-duplicate Enterobacteriaceae clinical isolates NS to at least one carbapenem and the total number of isolates of the different species. Carbapenem MICs were determined by broth microdilution and the β-lactamase content by DNA microarray.

Results: During the study period, the 71 laboratories identified 133 244 Enterobacteriaceae isolates, of which 846 (0.63%) were NS to at least one carbapenem. Carbapenem-NS isolates accounted for 0.07% (61/90 148) among Escherichia coli isolates, 1.1% (111/10 436) among Klebsiella pneumoniae, 8.2% (492/5971) among Enterobacter cloacae and 4.0% (84/2104) among Enterobacter aerogenes. Among the 541 available carbapenem-NS isolates, 222 (including 63 randomly selected E. cloacae) were further analysed after confirmation of carbapenem non-susceptibility. None of the Enterobacter spp. isolates produced carbapenemase. Among the other species, 28 isolates produced carbapenemases (22 OXA-48, 4 KPC and 2 NDM), accounting for an estimated proportion of carbapenemase-producing isolates of 0.08% for all species, 0.01% for E. coli and 0.27% for K. pneumoniae. The incidence-density rate in the participating hospitals was 0.0041 per 1000 hospital-days and the incidence rate was 0.0027 per 100 admissions.

Conclusions: The incidence-density rate of carbapenemase-producing isolates per 1000 hospital-days was low and 30-fold lower than that of carbapenem-NS isolates (0.125) and almost 300-fold lower than that of ESBL-producing isolates (1.104) in these French hospitals.