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Characteristics of a Colistin-Resistant Escherichia coli ST695 Harboring the Chromosomally-Encoded mcr-1 Gene.

ABSTRACT: Enterobacteriaceae having chromosomally-encoded mcr-1 is rarely reported. In this study, we recovered a chromosomal mcr-1 carrying Escherichia coli, designated HeN100, from the feces of a diarrheal pig in China. Antimicrobial susceptibility testing showed that HeN100 was resistant to three aminoglycosides, twelve ?-lactams including three carbapenems, one phenicol, two tetracyclines, two fluoroquinolones, nitrofurantoin, and colistin tested. Oxford Nanopore MinION sequencing revealed that the complete genomes of the multidrug resistant (MDR) HeN100 consisted of a single circular chromosome and five circular plasmids. Bioinformatical analysis determined HeN100 as ST695 and it contained many acquired resistance genes responsible for its MDR phenotypes, including colistin resistance mcr-1 and the carbapenem resistance blaNDM-1, and most of these genes were located on plasmids. However, the mcr-1 was found on the chromosome, and it was located between an IS30-like element ISApl1 and a PAP2-like encoding gene. These three genes consisted of an "ISApl1-mcr-1-orf" segment and inserted in high AT-rich regions. Finally, we found the blaNDM-1 was carried on an IncFII type conjugative plasmid. The conjugation frequency of this plasmid was 7.61? ± 2.11 ?× ?10-5 per recipient, and its conjugation conferred resistance to carbapenems and other ?-lactams, as well as aminoglycosides. The spread of this mcr-1/blaNDM-1-carrying E. coli ST695 represents a great concern of public health.

SUBMITTER: Peng Z

PROVIDER: S-EPMC6920969 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Characteristics of a Colistin-Resistant Escherichia coli ST695 Harboring the Chromosomally-Encoded mcr-1 Gene.

Peng Zhong Z Hu Zizhe Z Li Zugang Z Li Xiaosong X Jia Chaoying C Zhang Xiaoxue X Wu Bin B Chen Huanchun H Wang And Xiangru AX

Microorganisms 20191112 11

Enterobacteriaceae having chromosomally-encoded mcr-1 is rarely reported. In this study, we recovered a chromosomal mcr-1 carrying Escherichia coli, designated HeN100, from the feces of a diarrheal pig in China. Antimicrobial susceptibility testing showed that HeN100 was resistant to three aminoglycosides, twelve β-lactams including three carbapenems, one phenicol, two tetracyclines, two fluoroquinolones, nitrofurantoin, and colistin tested. Oxford Nanopore MinION seq ...[more]

PMID: 31726755

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Project description:The wide distribution of colistin-resistant bacteria in developing countries has become a common phenomenon. To understand the mechanisms underlying their distribution, we studied the mcr genetic background of colistin-resistant Escherichia coli isolates from the fecal microbiota of healthy human residents from a community in Vietnam with a high prevalence of colistin-resistant E. coli with mcr Fifty-seven colistin-resistant isolates were obtained from 98 residents; one isolate was collected from each individual and analyzed for mcr We found that 36.8% of the isolates carried chromosomal mcr-1 Further, 63.2% and 1.8% of the isolates carried mcr-1 on the plasmid and the plasmid/chromosome, respectively. Whole-genome sequencing of genetically unrelated isolates showed that the majority (6 of 7) of the isolates had the chromosomal mcr-1 in a complete ancestral mcr-1 transposon Tn6330, ISApl1-mcr-1-PAP2-ISApl1, which was inserted at various positions on the chromosomes. In addition, the majority (87.5%) of Tn6330 of mcr-1-carrying plasmids (n?=?8) lacked both upstream and downstream ISApl1 transposons. The results obtained in this study indicate that plasmid-to-chromosomal transfer of mcr-1 may have occurred recently in the fecal microbiota of the residents. Additionally, Tn6330 on the chromosome may lose ISApl1 from the transposon during multiplication to gain a more stable mcr-1 state on the chromosome. Stabilization of resistance by the chromosomal incorporation of mcr-1 would be an additional challenge in combating the dissemination of resistant bacteria.IMPORTANCE Elucidation of the mechanism of the wide dissemination of colistin-resistant bacteria in communities of developing countries is an urgent public health issue. In this study, we investigated the genetic background of the colistin resistance gene mcr in E. coli isolates from the fecal microbiota of healthy human residents living in a community in Vietnam with a high prevalence of colistin-resistant E. coli Our study revealed for the first time, a surprisingly high percentage (36.8%) of colistin-resistant E. coli carrying chromosomal mcr-1, the emergence of which may have occurred recently, in the fecal microbiota of the community residents. The mcr-1 transposon on the chromosome may develop into a more stable genotype by the loss of insertion sequences (ISs). Our results are valuable in understanding the mechanism underlying the increasing prevalence of colistin-resistant bacteria within a community.

Dataset Information

Characteristics of a Colistin-Resistant Escherichia coli ST695 Harboring the Chromosomally-Encoded mcr-1 Gene.

Publications

Characteristics of a Colistin-Resistant <i>Escherichia coli</i> ST695 Harboring the Chromosomally-Encoded m<i>cr-1</i> Gene.

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