Characteristics of carbapenemase-producing Klebsiella pneumoniae as a cause of neonatal infection in Shandong, China

Abstract

The goal of the present study was to examine the characteristics of carbapenem-resistant <i>Klebsiella pneumoniae</i> as a cause of neonatal infection. A total of 37 carbapenem-resistant <i>Klebsiella pneumoniae</i>-positive newborns hospitalized in Shandong Provincial Hospital, China between April 2011 and October 2013 were examined. Antibiotic susceptibility testing was performed using the agar dilution method and the Etest. Resistance genes were assessed by polymerase chain reaction (PCR) and sequencing. Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) were used to determine the genotypes and homology of these isolates. Plasmids were analyzed by PFGE and conjugation experiments. The outer membrane proteins were examined by PCR and SDS-PAGE. All of the isolates were revealed to be resistant to the third and fourth generation cephalosporins and piperacillin-tazobactam. Tigecycline, colistin, levofloxacin and amikacin were successful against all of the isolates. The antibiotic resistance rates of aztreonam, gentamicin, trimethoprim-sulfamethoxazole and fosfomycin were 13.51, 48.64, 78.38 and 86.49%, respectively. Of the 37 cases, 25 isolates (67.57%) were bla_NDM-1 positive, 13 isolates (35.14%) were bla_IMP-4 positive and 1 isolate (2.70%) was bla_IMP-8 positive. Two isolates carried both bla_NDM-1 and bla_IMP-4. The isolate carrying 2-4 plasmids and bla_NDM-1 and bla_IMP-4 was transferable between strains. SDS-PAGE data indicated that outer membrane proteins remained present. PFGE revealed 7 distinct clusters, and MLST reported the presence of ST20, ST17, ST54, ST705 and ST290 sequences, which indicated that there was clone and plasmid spread between newborns. The main resistance mechanism of carbapenem-resistant <i>Klebsiella pneumoniae</i> was that the isolates expressed the carbapenemase resistance of bla_NDM-1 and bla_IMP-4 genes. The current study indicates that early detection of these genes may be helpful in infection prevention and control.