Abstract
Extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) strains are emerging around the world as a source of resistance to β-lactam antibiotics such as ampicillin, cefotaxime, and ceftazidime. mcr-1 is a novel plasmid-mediated gene conferring resistance to colistin. The aim of this study was to investigate the prevalence of ESBL-EC mcr-1 of chicken origin in the different provinces of China during 2008–2014. Overall, 341 of 821 isolates were determined to be ESBL-EC strains, and the proportion of ESBL-positive strains almost doubled from 2008 to 2014. The findings of our study revealed regional differences, with significantly more ESBL-EC isolates from stockbreeding in concentrated poultry industry areas in Shandong than from the other four provinces. The ESBL type analysis showed that bla CTX-M was the most prevalent ESBL-encoding gene (92.7%). In total, twelve subtypes of CTX-M genes were detected, among which, bla CTX-M-55 (34.3%) and bla CTX-M-65 (17.9%) were the major identified genotypes. In addition, bla TEM and pAmpC genes were carried by 86.0% and 8.5% of isolates, respectively. In this study, we also observed 44 E. coli isolates with multiple ST types (ST46, ST1286, ST10, ST29, ST101, and ST354) carrying mcr-1, and the majority of mcr-1–carrying plasmids were IncI2. The whole-genome sequencing analysis indicated the co-existence of bla CTX-M and mcr-1 in ESBL-EC of both animal and human origin, and phylogenetic analysis further revealed their close relationship, especially several isolates sharing a small number of SNPs, which suggested the increasing trend of co-existence and transmission of ESBL and mcr-1 in both clinical medicine and veterinary medicine.
Highlights
Antibiotic resistance in bacteria has become one of the major threats to public health because of the extensive use of antibiotics in human medicine and animal farming
To evaluate the co-existence and prevalence of ESBL and mcr-1 in E. coli of chicken origin, we investigated the trends of Extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) prevalence in chickens in the different provinces of China from 2008 to 2014 and further elucidated the predominant genotype of ESBL and the phylogenetic relationship among ESBL-EC carrying mcr-1
Prevalence of ESBL-EC We obtained 341 ESBL-EC strains from 821 isolates of chicken origin (Table 1), and the ESBL-EC increased from 23.8% in 2008 to 57.0% in 2014 (Fig. 1)
Summary
Antibiotic resistance in bacteria has become one of the major threats to public health because of the extensive use of antibiotics in human medicine and animal farming. Global antimicrobial consumption in food animal production may increase by 67% by 2030, driven primarily by BRICS (Brazil, Russia, India, China, and South Africa) countries, as large-scale and intensive farming operations are heavily in demand with the rise in income and meat consumption[1]. 50% of total antibiotic production is used routinely in subtherapeutic doses for growth promotion, and this corresponds to a consumption of antimicrobials per kilogram of animal produced of ~148 mg kg−1 in chicken production[3]. The rapid increase in the multi-drug resistance of E. coli has been observed in clinical medicine[4], and widely in food animal production[5], with an increasing prevalence of ESBL and AmpC β-lactamase producing strains, which greatly.
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