Abstract
The emergence and dissemination of carbapenem-resistant Enterobacteriaceae (CRE) is a growing concern to animal and public health. However, little is known about the spread of CRE in food and livestock and its potential transmission to humans. To identify CRE strains from different origins and sources, 53 isolates were cultured from 760 samples including retail meat products, patients, and porcine excrement. Antimicrobial susceptibility testing was carried out, followed by phylogenetic typing, whole-genome sequencing, broth mating assays, and plasmids analyses. Forty-three Escherichia coli, nine Klebsiella pneumoniae, and one Enterobacter cloacae isolates were identified, each exhibiting multidrug-resistant phenotypes. Genetically, the main sequence types (STs) of E. coli were ST156 (n = 7), ST354 (n = 7), and ST48 (n = 7), and the dominant ST of K. pneumoniae is ST11 (n = 5). blaNDM–5 (n = 40) of E. coli and blaKPC–2 (n = 5) were the key genes that conferred carbapenem resistance phenotypes in these CRE strains. Additionally, the mcr-1 gene was identified in 17 blaNDM-producing isolates. The blaNDM–5 gene from eight strains could be transferred to the recipients via conjugation assays. Two mcr-1 genes in the E. coli isolates could be co-transferred along with the blaNDM–5 genes. IncF and IncX3 plasmids have been found to be predominantly associated with blaNDM gene in these strains. Strains isolated in our study from different sources and regions tend to be concordant and overlap. CRE strains from retail meat products are a reservoir for transition of CRE strains between animals and humans. These data also provide evidence of the dissemination of CRE strains and carbapenem-resistant genes between animal and human sources.
Highlights
The abuse of antibiotics has led to a crisis of antibiotic resistance, which has become a formidable threat to public health in China and around the globe
The aims of this study were (i) to reveal the emergence of carbapenemresistant Enterobacteriaceae (CRE) isolates cultured from retail meat products, pig feces, and patients in China; (ii) to identify the genes relating to carbapenem resistance; (iii) to characterize the donor isolates by phylogenetic grouping and multi-locus sequence typing (MLST); and (iv) to determine the co-transferred resistance markers by conjugation assays along with S1-nuclease-based plasmid profiles
Thirty-six isolates were cultured from retail meat products from Shijiazhuang and Zhengzhou, including 30 E. coli, 5 K. pneumoniae, and 1 Enterobacter cloacae
Summary
The abuse of antibiotics has led to a crisis of antibiotic resistance, which has become a formidable threat to public health in China and around the globe. Increasing antibiotic consumption has been accompanied by the emergence of antibiotic-resistant Gram-negative pathogens (Xu et al, 2015). Multidrug-resistant bacteria (MDRs), especially Gram-negative bacteria resistant to carbapenems, known as carbapenemresistant Enterobacteriaceae (CRE), are the most critical (Wang et al, 2015). Carbapenems are the favored last-resort antibiotics for treatment of MDR infection. Meropenem (MEM) and imipenem (IMI) are the two most clinically used carbapenems. These are increasingly ineffective with the emergence of carbapenemase in CRE. CRE cause hard-to-treat infections among hospitalized patients (Zhang R. et al, 2017).
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