Outbreak of pulmonary infection caused by Klebsiella pneumoniae isolates harbouring b/aIMP-4 and b/aDHA-1 in a neonatal intensive care unit in China

Outbreaks caused by Klebsiella pneumoniae producing carbapenemases and other beta-lactamases have been reported. Four neonates admitted to a neonatal intensive care unit (NICU) in a Chinese hospital developed respiratory infection while receiving intensive care. In all four cases, multidrug-resistant K. pneumoniae was isolated from multiple respiratory specimens, leading to additional characterization of these organisms and investigation of the local environment in the NICU. Multiple beta-lactamase genes, including b/a(TEM-1), b/a(IMP-4), b/a(DHA-1) and b/a(CTX-M-14), as well as the quinolone resistance gene qnrB4, were harboured by transferable plasmids from all four clinical isolates. Furthermore, PFGE confirmed that three of the four clinical isolates from the patients and three K pneumoniae isolates collected from the hands of healthcare workers and an incubator in the NICU belonged to the same PFGE cluster, indicating that an outbreak due to multidrug-resistant K pneumoniae carrying b/a(IMP-4) and b/a(DHA-1) occurred in this NICU. As far as is known, this is the first report of the co-existence of b/a(IMP-4) and b/a(DHA-1) in the same K pneumoniae isolate. These data suggest that additional precautions are needed to prevent outbreaks of infection caused by multidrug-resistant K. pneumoniae resulting from environmental exposure in NICUs.