Spread of the mcr-1 colistin-resistance gene in Escherichia coli through plasmid transmission and chromosomal transposition in French goats

Abstract

IntroductionColistin-resistance widely disseminated in food-producing animals due to decades of colistin use to treat diarrhea. The plasmid-borne mcr-1 gene has been extensively reported from bovine, swine and chicken worldwide, but smaller productions such as the goat farming sector were much less surveyed.MethodsWe looked for colistin-resistant isolates presenting plasmid-borne genes of the mcr family in both breeding (n=80) and fattening farms (n=5). Localization of the mcr-1 gene was performed using Southern blot analysis coupled to short-read and long-read sequencing.ResultsOnly the mcr-1 gene was identified in 10% (8/80) of the breeding farms and four over the five fattening farms. In total, 4.2% (65/1561) of the animals tested in breeding farms and 60.0% (84/140) of those tested in fattening farms presented a mcr-1-positive E. coli. The mcr-1 gene was located either on the chromosome (32.2%) or on IncX4 (38.9%) and IncHI2 (26.8%) plasmids. As expected, both clonal expansion and plasmidic transfers were observed in farms where the mcr-1 gene was carried by plasmids. Tn6330 transposition was observed in the chromosome of diverse E. coli sequence types within the same farm.DiscussionOur results show that the mcr-1 gene is circulating in goat production and is located either on plasmids or on the chromosome. Evidence of Tn6330 transposition highlighted the fact that chromosomal insertion does not impair the transmission capability of the mcr-1 gene. Only strict hygiene and biosecurity procedures in breeding farms, as well as a prudent use of antibiotics in fattening farms, can avoid such complex contamination pathways.

Repeated Occurrence of Mobile Colistin Resistance Gene-Carrying Plasmids in Pathogenic Escherichia coli from German Pig Farms

“…The majority of plasmid types were IncX4 (35.2%), IncI2 (34.7%) and IncHI2 (20.5%), with a significant geographical clustering of IncHI2 plasmids in Europe and a regional spread of IncI2 plasmids in Asia. A recent study from France investigated the occurrence of mcr-1-mcr-5 and mcr-9 genes in colistin-resistant E. coli isolates obtained from over 1500 goats of 80 breeding and five fattening goat farms [57]. In total, 149 mcr-1-positive E. coli were identified, with 146 mcr-1 genes located on either IncX4 (38.9%) or IncHI2 (26.8%) plasmids and on the chromosome (32.2%).…”

Epidemiology and zoonotic transmission of mcr-positive and carbapenemase-producing Enterobacterales on German turkey farms

“…However, to improve the comparative techniques, plasmid-typing of mcr -Col-E isolates from humans and the farm environment was also performed: the mcr gene was contained by two different replicon family types: IncX4 and IncHI2. They have both been found among the most prevalent mcr -carrying plasmids not only in Germany ( Falgenhauer et al, 2016 ; Roschanski et al, 2017 ) and other European countries such as Denmark ( Hasman et al, 2015 ), the Netherlands ( Veldman et al, 2016 ), France ( Haenni et al, 2016 ; Treilles et al, 2022 ), the United Kingdom ( Doumith et al, 2016 ), Switzerland ( Zurfluh et al, 2017 ), and Spain ( Migura-Garcia et al, 2020 ) but also in Asia ( Matamoros et al, 2017 ). Comparing the plasmids harbouring mcr genes from human and environmental isolates from the same farm, there was one case with a similar plasmid backbone and identical mcr environment, pointing towards zoonotic transmission.…”