Abstract
The continuous emergence of carbapenem-resistant Escherichia coli (CRECO) presents a great challenge to public health. New Delhi metallo-lactamase (NDM) variants are widely disseminated in China, so the research on the prevalence and transmission of diverse blaNDM variants is urgently needed. In the present study, 54 CRECO isolates were collected from 1,185 Escherichia coli isolates in five hospitals in Northern Jiangsu Province, China from September 2015 to August 2016. Antimicrobial susceptibility tests, PCR detection of resistance determinants, multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were performed to characterize these strains. Plasmid conjugation experiments were carried out to determine the transferability of resistant genes from selected isolates. PCR-based replicon typing (PBRT), S1 nuclease-PFGE, and Southern blotting were conducted for plasmid profiling. Carbapenemase genes were detectable in all CRECO isolates, among which thirty-one CRECO isolates were found to carry blaNDM−5 (54.7%), while, blaNDM−1, blaNDM−7, blaNDM−4, blaNDM−9, and blaKPC−2 were identified in 14, five, two, one, and one isolates, respectively. MLST results revealed 15 different STs and four new STs were first reported to be linked with NDM-producing isolates. PFGE typing showed that no more than two isolates with the same ST appeared to the same band pattern except three ST410 isolates. Twenty-six selected NDM-producing isolates were successfully transferred to E. coli J53 by conjugation experiments. Notably, 50.0% (13/26) of blaNDM variants were found to be carried by ~55 kb IncX3 plasmid. Our study reported a high prevalence of blaNDM variants, especially blaNDM−5, in Northern Jiangsu province, China. Diverse blaNDM variants were mainly carried by ~55 kb IncX3 plasmids, suggesting that the fast evolution and high transferability of this kind of plasmid promote the high prevalence of blaNDM variants. Therefore, large-scale surveillance and effective infection control measures are also urgently needed to prevent diverse blaNDM variants from becoming epidemic in the future.
Highlights
Carbapenem, a β-lactam that is highly potent against Gramnegative bacteria, has been recognized as a last resort for treating of infections caused by multidrug-resistant bacteria
A total of 54 (4.56%, 54/1185) non-duplicate E. coli isolates that exhibited resistance to imipenem or meropenem were obtained from five hospitals in Northern Jiangsu Province, China
Five different blaNDM variants were identified in this collection (Figure 1)
Summary
Carbapenem, a β-lactam that is highly potent against Gramnegative bacteria, has been recognized as a last resort for treating of infections caused by multidrug-resistant bacteria. The increasing number of carbapenem-resistant Enterobacteriaceae (CRE) is unexpected despite infection control efforts, and it poses a great challenge to clinic (Zilberberg and Shorr, 2013). New Delhi metallo-lactamase (NDM), was first reported in a Swedish patient with a hospitalization history in India, it exhibited resistant to all β-lactams except for monobactams, and has great potential to cause global health crisis (Yong et al, 2009). An increasing number of regions worldwide have reported that patients with blaNDM−positive isolates have never been abroad, indicating that blaNDM genes are associated with some special clones (Leverstein-Van et al, 2010)
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