Resistance mechanism and molecular epidemiology of the New Delhi metallo-β-lactamase-1 possessing Klebsiella pneumoniae / 中华检验医学杂志

ABSTRACT

Objective To investigate the molecule phenotype, epidemiology, and resistance genes of the New Delhi metallo- β-lactamase-1 ( NDM-1 ) producing Klebsiella pneumoniae ( K. pneumoniae ) . Methods Retrospective study was made on one hundred and ten non-repetitive carbepenem-resistant K. pneumoniae clinical isolated strains, which were collected from January 2011 to December 2012 in our hospital. The minimal inhibitory concentrations ( MICs ) of antibiotics were tested by the GN13 cards of BioMerieux Company. Modified Hodge test were used for the detection of carbapenemases. The blaNDM-1 encoding gene and linkage of ISAba125-NDM were detected by PCR method. The purified PCR products were cloned and sequenced. The homology of the K. pneumoniae were analyzed by the multilocus sequence typing ( MLST ) . Plasmid conjugation experiment and curing method were used to study the transfer of bacterial resistance. The Fisher′s exact probability test was used to compare the data. Results 13% NDM-1-producing K. pneumoniae were detected and confirmed as blaNDM-1 by sequencing (14/110). The resistance rates of the 14 NDM-1-producing K. pneumoniae strains to imipenem, meropenem, ertapenem, ciprofloxacin, levofloxacin, amikacin, and aztreonam were 14/14, 14/14, 13/14, 10/14, 9/14, 5/14, and 11/14. Meanwhile, the positive rate of ISAba125-NDM linkage of those 14 NDM-1-producing K. pneumoniae strains was 14/14. The E. coli J53 transconjugants, whose MICs of imipenem, meropenem, and ertapenem were increased by 4 to 64 times, were blaNDM-1 gene and ISAba125-NDM linkage positive. In addition, it was showed that the blaNDM-1 gene and ISAba125-NDM linkage were located on a plasmid with a size of approximately 65 000 bp. Conclusions The NDM-1 producing K. pneumoniae strains in this study were resistant to many commonly used antibiotics, however, the resistance rate to aminoglycoside and aztreonam were relatively low. The carbapenemase-resistant genotype spread by blaNDM-1 carried plasmid. Attention should be paid to its easily transmissible feature among the strains in clinic. The insertion sequence ISAba125 may be involved in the blaNDM-1 gene mediated carbapenemase-resistant genotype.