Abstract
The emergence of carbapenem-resistant and colistin-resistant Enterobacteriaceae represents a great risk for public health. In this study, the phenotypical and genetic characteristics of eight carbapenem-resistant and colistin-resistant isolates from pig farms in China were determined by the broth microdilution method and whole genome sequencing. Antimicrobial susceptibility testing showed that the eight carbapenem-resistant and colistin-resistant strains were resistant to three aminoglycosides, twelve β-lactams, one of the phenicols, one of the tetracyclines, and one of the fluoroquinolones tested, simultaneously. The prediction of acquired resistant genes using the whole genome sequences revealed the co-existence of blaNDM-1 and mcr-1 as well as the other genes that were responsible for the multidrug-resistant phenotypes. Bioinformatics analysis also showed that the carbapenem-resistant gene blaNDM-1 was located on a putative IncFII-type plasmid, which also carried the other acquired resistant genes identified, including fosA3, blaTEM-1B and rmtB, while the colistin-resistant gene mcr-1 was carried by a putative IncX4-type plasmid. Finally, we found that these resistant genes/plasmids were conjugative, and they could be co-conjugated, conferring resistance to multiple types of antibiotics, including the carbapenems and colistin, to the recipient Escherichia coli strains.
Highlights
Escherichia coli has become a great concern for global public health
The plasmid-mediated blaNDM-1 confers resistance to carbapenems [6], which is considered as the last resort for treating multidrug-resistant (MDR) Enterobacteriaceae [8], while mcr-1 mediates the resistance to colistin [9], the key antibiotic used for treating carbapenem-resistant Enterobacteriaceae [8]
We report several carbapenem-resistant and colistin-resistant E. coli co-producing NDM-1 and MCR-1 from pig farms in China
Summary
Escherichia coli has become a great concern for global public health. On the one hand, the prevalence and outbreak of some intestinal pathogenic E. coli clones, the well-known O157/ST11 and, more recently, the O104/ST678, has caused high levels of morbidity and mortality worldwide [1,2,3,4]; on the other hand, E. coli has had a great capacity to accumulate resistance genes, representing a natural reservoir of resistance genes, which may contribute to the dissemination of antibiotic resistance and lead to treatment failures in both human and veterinary medicine [5]. The emergence of the plasmid-mediated New Delhi metallo-β-lactamase-1 encoding gene blaNDM-1 and/or the plasmid-mediated colistin-resistance gene mcr-1 represents a great concern to global public health [6,7]. The emergence of carbapenems and colistin co-resistant Enterobacteriaceae means there will be little and/or no antibiotic available for the infections caused by such strains in most cases of infections caused by MDR Enterobacteriaceae. The co-existence of blaNDM and mcr-1 in Enterobacteriaceae originated from both humans and animals has been increasingly reported worldwide [10,11,12,13]. Of concern is the recovery of an E. coli strain co-producing MCR-1 and NDM-9 from a patient with a catheter-associated urinary tract infection (UTI); the infection of such an E. coli led to the failure of antibiotic treatment and killed the patient [10]. We report several carbapenem-resistant and colistin-resistant E. coli co-producing NDM-1 and MCR-1 from pig farms in China
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