Outbreak of nosocomial NDM-1-producing Klebsiella pneumoniae ST1419 in a neonatal unit.

OBJECTIVES: The aim of this study was to characterise carbapenem-resistant Klebsiella pneumoniae isolates recovered from neonatal clinical specimens over a 4-month period.

METHODS: Seven carbapenem-resistant K. pneumoniae isolates were analysed. Antibiotic susceptibilities of the isolates were determined by the agar dilution method, and the drug resistance genes were evaluated by PCR. Clonal relatedness of the isolates was assessed using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Conjugation experiments and Southern blot hybridisation were performed to determine the transferability of the plasmids.

RESULTS: All of the K. pneumoniae isolates carried the blaNDM-1 gene but were negative for all other carbapenemases tested. All of the isolates harboured blaSHV-12, and five isolates also carried blaCTX-M-15 and/or blaTEM-1. All of the isolates exhibited multidrug resistance. The isolates belonged to sequence types ST1419 and ST101 and formed three different PFGE patterns. Plasmids carrying blaNDM-1 were successfully transferred from six of the seven isolates to the Escherichia coli recipient. These six NDM-1-producing K. pneumoniae were clonal and carried blaNDM-1 on the same plasmid, but one isolate possibly carried chromosomal blaNDM-1.

CONCLUSIONS: This is the first report of NDM-1-positive K. pneumoniae ST1419 from neonates in China. Closer attention should be paid to monitoring blaNDM-1 gene dissemination because it is potentially transferred horizontally.