High Prevalence of Colistin-Resistant Escherichia coli with Chromosomally Carried mcr-1 in Healthy Residents in Vietnam

Abstract

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 ϭ 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 colistinresistant 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.

Emergence of Nosocomial Pneumonia Caused by Colistin-Resistant Escherichia coli in Patients Admitted to Chest Intensive Care Unit

“…Another alarming rate for colistin resistance in Egypt was reported among cancer patients, where 8.8% of Klebsiella pneumoniae (K. pneumoniae) and E. coli strains were colistin-resistant [63]. In agreement with different reports, in our study, resistance to colistin was mediated by the presence of the mcr-1 gene, which is responsible for the addition of phosphoethanolamine to the lipid A fraction of the cell wall [64][65][66]. However, we did not test the presence of the recently reported types of mcr such as mcr 6-10 or the pmrA/B and phoP/Q genes.…”

“…In Portugal, screening of 100 rectal swabs from pigs revealed 98 mcr-1-positive isolates [71]. It is possible that persistent exposure to low levels of colistin, such as those originating from the use of colistin-containing poultry food, led to the development of colistin resistance [64].…”

Association of the colistin resistance gene mcr‐1 with faecal pollution in water environments in Hanoi, Vietnam

“…Furthermore, other mcr variants appeared in China as well as Europe and the USA (Rebelo et al 2018;Gharaibeh and Shatnawi 2019;Borowiak et al 2020). Recent study demonstrated that some Escherichia coli carried chromosomal mcr-1 (Yamaguchi et al 2020). The rapid spread of mcr-1 associated with humans and animals has been observed globally (von Wintersdorff et al 2016;Al-Tawfiq et al 2017;Wang et al 2018).…”

<strong>Acquisition of Multidrug-Resistant Bacteria and Colistin Resistance Genes in French Medical Students on Internships Abroad</strong>

“…We observed that the primary travel destination being Vietnam was associated with a higher risk of acquisition of colistin resistance genes. Yamaguchi et al, revealed a high percentage (36.8%) of colistin-resistant E. coli carrying chromosomal mcr-1 in the faecal microbiota of a community of Vietnam residents [58]. In this study, we revealed that 40% of students who participated in a school renovation project in Vietnam became carriers of mcr genes.…”