Antimicrobial resistant mechanisms of carbapenem-resistant Klebsiella pneumonia infection in newborns / 中华检验医学杂志

ABSTRACT

Objective To investigate the antimicrobial resistant and transmission mechanisms of carbapenem-resistant K.pneumonia (CR-KP) infection of newborns.Methods A retrospective study was conducted on totally 37 non-repetitive CR-KP which were isolated from patients hospitalized between April 2011 and October 2013.Resistance genes were identified by PCR and sequencing.Plasmid was analyzed by pulsed-field gel electrophoresis (PFGE).Conjugation experiments were performed to determine the transferability of beta-lactamase.Multilocus sequence typing (MLST) was used to determine the genotypes and homology of these isolates.Out-membrane proteins were examined by PCR and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).Results Thirty-seven CR-KP isolates were tested.The resistant rates of imipenem, meropenem, ertapenem were 89.2％ (33/37), 83.8％ (31/37) ,97.3％ (36/ 37), respectively.All the 37 CR-KP exhibited 100％ (37/37) sensitivity to tigecycline, colistin, levofloxacin and amikacin, while resistance to most of the other antibiotics.By PCR, 67.6％ (25/37) isolates were blaNDM-1 positive, 35.1％ (13/37) isolates were blaIMP-4 positive and 2.7％ (1/37) isolate were blaIMP-8 positive, including two isolates carrying both blaNDM-1 and blaIMP-4.PFGE results showed that the isolates carried 2-4 plasmids and both blaNDM-1 and blaIMP-4 were transferable by plasmids.MLST assigned them to sequence type (ST) 20, ST17, ST54, ST705, ST290,which showed that there were infectious outbreaks caused by NDM-1-producing and IMP-4-producing respectively among newborns.SDS-PAGE result indicated that there was no absence of outer membrane proteins OmpK35 and OmpK36.Conclusions The main resistant mechanisms of CR-KP causing infection in newborns were those the isolates carried carbapenemase of blaNDM-1 or blaIMP-4 and the K.pneumonia with two kinds of carbapemenase were detected.