Molecular Epidemiology of Clonally Related Metallo-β-Lactamase-Producing Klebsiella pneumoniae Isolated from Newborns in a Hospital in Shandong, China

Background: The infection caused by metallo-β-lactamase (MBL)-producing Klebsiella pneumoniae has become a challenge to anti- infection treatments for newborns. Objectives: The aim of this study is to investigate the molecular epidemiological characteristics of clonally related MBL-producing K. pneumoniae isolated from newborns in a hospital in Northern China. Methods: A total of 16 isolates of carbapenem-resistant K. pneumonia were obtained from newborns between September 2011 and June 2014. Resistance genes were identified by PCR and sequencing. The isolates were classified by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Results: Our results show that the most prevalent genotypes of carbapenem-resistant K. pneumonia were ST54 and ST705. There were respectively 6 strains and 9 strains of K. pneumonia ST54 harboring the blaNDM-1 and blaIMP-4 genes, while the K. pneumoniae ST705 harbored the blaIMP-4 gene. Other resistance genes included extended-spectrum β-lactamases, plasmid-mediated AmpC enzymes and a class 1 gene cassette. The transferability of metallo-β-lactamase was determined by conjugation experiments, which showed that the blaNDM-1 and blaIMP-4 genes were transferable and likely through a plasmid-mediated event. Conclusions: Our results showed that New Delhi metallo-beta-lactamase-1 (NDM-1) and imipenemase-4 (IMP-4) carbapenemases were the major players responsible for the carbapenem-resistance. Co-production of NDM-1 with CTX-M-15 in K. pneumoniae isolates was detected for the first time in our neonatal intensive care unit. Early detection of these drug resistance genes will help in preven- tion and control of the infection of K. pneumonia.