The prevalence of carbapenemase genes and plasmid-mediated quinolone resistance determinants in carbapenem-resistant Enterobacteriaceae from five teaching hospitals in central China

Abstract

We investigated the prevalence of β-lactamase genes and plasmid-mediated quinolone resistance (PMQR) determinants in 51 carbapenem-resistant Enterobacteriaceae (CRE) from five teaching hospitals in central China. The prevalence of carbapenem resistance in Enterobacteriaceae was 1.0% (51/5012). Of 51 CRE, 31 (60.8%) isolates were positive for one tested carbapenemase gene, while 10 (19.6%) were simultaneously positive for two tested carbapenemase genes. The positive rates of blaKPC-2, bla NDM-1, blaIMP-4, blaIMP-26 and bla IMP-8 were 54.9%, 17.6%, 11.8%, 11.8% and 3.9%, respectively. Of 10 CRE with two carbapenemase genes, three, five, one and one were positive for blaKPC-2 and blaIMP-4, blaKPC-2 and bla IMP-26, blaKPC-2 and blaIMP-8, and bla KPC-2 and blaNDM-1, respectively. Eight of nine bla NDM-1-positive isolates lacked carbapenemases by the modified Hodge test, while 27/28 isolates harbouring blaKPC-2 were positive for carbapenemases determined by this test; 41.2% of the CRE-positive isolates also harboured ESBL genes in various combinations (three and two positive for blaKPC-2 also carried blaDHA-1 and blaCMY-2). The positive rates of qnrS1, qnrA1, qnrB and aac-(6/)-Ib-cr in CRE were 25.5%, 9.8%, 23.5% and 15.7%, respectively. In particular, 7/9 isolates harbouring blaNDM-1 were positive for these quinolone resistance genes, of which five carried qnrS1 and two carried qnrS1 and qnrB4. All but two of 29 Klebsiella pneumoniae isolates were grouped into 20 clonal clusters by PFGE, with the predominant cluster accounting for four blaKPC-2- positive isolates distributed in the same hospital. We conclude that there is a high prevalence of blaNDM-1 and PMQR determinants in CRE isolates in central China. Multiple resistance determinants in various combinations co-exist in these strains and we report for the first time the co-existence of bla KPC-2 and blaIMP-26 in a strain of Klebsiella oxytoca. Copyright © Cambridge University Press 2013.