High Incidence and Endemic Spread of NDM-1-Positive Enterobacteriaceae in Henan Province, China

Abstract

ABSTRACTThe emergence and spread of New Delhi metallo-β-lactamase 1 (NDM-1)-producing carbapenem-resistantEnterobacteriaceae(CRE) present an urgent threat to human health. In China, theblaNDM-1gene has been reported mostly inAcinetobacterspp. but is rarely found inEnterobacteriaceae. Here, we report a high incidence and endemic spread of NDM-1-producing CRE in Henan Province in China. Sixteen (33.3%) of the 48 CRE isolates obtained from patients during June 2011 to July 2012 were positive forblaNDM-1, and the gene was found to be carried on plasmids of various sizes (∼55 to ∼360 kb). These plasmids were readily transferrable to recipientEscherichia coliby conjugation, conferred resistance to multiple antibiotics, and belonged to multiple replicon types. TheblaNDM-1-positive CRE isolates were genetically diverse, and six new multilocus sequence typing (MLST) sequence types were linked to the carriage of NDM-1. Five of the isolates were classified as extensively drug-resistant (XDR) isolates, four of which also carried thefosA3gene conferring resistance to fosfomycin, an alternative drug for treating infections by CRE. In eachblaNDM-1-positive CRE isolate, theblaNDM-1gene was downstream of an intact ISAba125element and upstream of thebleMBLgene. Furthermore, gene environment analysis suggested the possible transmission ofblaNDM-1-containing sequences fromAcinetobacterspp. toKlebsiella pneumoniaeandKlebsiella oxytoca. These findings reveal the emergence and active transmission of NDM-1-positive CRE in China and underscore the need for heightened measures to control their further spread.