Transmission of Similar Mcr-1 Carrying Plasmids among Different Escherichia coli Lineages Isolated from Livestock and the Farmer

Abstract

Colistin use has mostly been stopped in human medicine, due to its toxicity. However, nowadays, it still is used as a last-resort antibiotic to treat hospital infections caused by multi-drug resistant Enterobacteriaceae. On the contrary, colistin has been used in veterinary medicine until recently. In this study, 210 fecal samples from pigs (n = 57), calves (n = 152), and the farmer (n = 1) were collected from a farm where E. coli harboring mcr-1–mcr-3 was previously detected. Samples were plated, and mcr-genes presence was confirmed by multiplex-PCR. Hybrid sequencing which determined the presence and location of mcr-1, other antibiotic resistance genes, and virulence factors. Eighteen colistin resistant isolates (13 from calves, four from pigs, and one from the farmer) contained mcr-1 associated with plasmids (IncX4, IncI2, and IncHI2), except for two that yielded mcr-1 in the chromosome. Similar plasmids were distributed in different E. coli lineages. Transmission of mcr-1 to the farmer most likely occurred by horizontal gene transfer from E. coli of calf origin, since plasmids were highly similar (99% coverage, 99.97% identity). Moreover, 33 virulence factors, including stx2 for Shiga toxin E. coli (STEC) were detected, highlighting the role of livestock as a reservoir of pathotypes with zoonotic potential.

Longitudinal Monitoring Reveals Persistence of Colistin-Resistant Escherichia coli on a Pig Farm Following Cessation of Colistin Use

“…In the central area of Thailand, the antimicrobials that are mainly used are colistin, cephalosporins, tiamulin, amoxicillin, tilmicosin, aminoglycosides (gentamycin), and oxytetracycline ( 50 ). The use of other antimicrobials during the production cycle of pigs could co-select for colistin resistance ( 51 , 52 ). Resistances to other potential agents like heavy metals or biocides that may be linked with antibiotics resistance genes also are a matter for concern.…”

A Review of Current Bacterial Resistance to Antibiotics in Food Animals

“… Vines et al (2021) collected 210 fecal samples from farm animals and the farmer and analyzed the spread of mcr -associated with plasmids among E. coli by multiplex PCR. It was identified 18 colistin-resistant E. coli isolates carrying mcr -1 (including 13 from calves, four from pigs, and one from the farmer, respectively) and 33 virulence factors.…”

“…It was identified 18 colistin-resistant E. coli isolates carrying mcr -1 (including 13 from calves, four from pigs, and one from the farmer, respectively) and 33 virulence factors. Moreover, the mcr -1 gene was transferred from the calf to the farmer, posing the risk of a farm as a reservoir of ARB with zoonotic potential ( Vines et al, 2021 ).…”

mcr-1-Mediated Colistin Resistance and Genomic Characterization of Antimicrobial Resistance in ESBL-Producing Salmonella Infantis Strains from a Broiler Meat Production Chain in Italy

“…It is known the ability of the mcr cassette to jump into several types of plasmids, including the IncX4 plasmid, which seems to be one of the predominant replicon types of plasmids, carrying the mcr-1 gene [ 15 ]. Moreover, the possibility of the transmission of mcr -positive IncX4 plasmids among different bacterial species, and from animals to humans or vice versa, has been documented, as reported elsewhere [ 37 ]. The WGS revealed that all six isolates carried blaCTX-M1 , tet(A) , dfrA1 and sul1 genes, mediating cefotaxime, tetracycline, trimethoprim and sulfonamide resistance, respectively.…”