Evaluation of carbapenem-resistant Enterobacteriaceae in an Italian setting: Report from the trench

The spread of carbapenem resistant Enterobacteriaceae (CRE) has recently become a matter of concern in public health, mainly due to the wide distribution of carbapenemase genes. Italy is a country considered endemic for the spread of bla_KPC Klebsiella pneumoniae (KP). The aim of this study was to depict the epidemiological trend of CRE in one Italian hospital over a long period (3years surveillance, from May 2011 to April 2014). Based on defined MIC cut-off for specific carbapenems, 164 strains isolated from 146 different patients were analyzed both phenotypically and genotypically to establish the resistance genes. Molecular typing was performed using the RAPD technique. 77 strains were demonstrated to harbor the bla_KPC gene (73 KP, 4 Escherichia coli - EC), 51 strains the bla_VIM gene (44 KP, 3 EC, 2 Enterobacter cloacae and 2 Klebsiella oxytoca), 8 the bla_NDM gene (3 KP, 4 EC and one Providencia stuartii), 3 the bla_OXA-48 gene (2 KP, 1 EC), whereas 25 out of the 164 isolates (of different genera and species) had a negative multiplex-PCR amplification for all the targets tested. 39 out of the 164 strains analyzed (23.8%) revealed discrepancies between the MICs obtained with automated instrument and gradient MICs of more than two logs of difference; the broth microdilution provided a better agreement with the results obtained with the gradient MIC. The use of RAPD allowed to distinguish different clusters, closely related, both for bla_KPC and for bla_VIM KP.