Domestic travel in China substantially contributes to the dissemination of mcr-1, with 14.8% of healthy travelers acquiring mcr-1-positive E. coli, driven by residence near poultry farms and diarrhea during travel.
14.8% of healthy travelers who were mcr-1 negative at baseline acquired mcr-1-positive Escherichia coli (MCRPEC) after domestic travel in China.
Residence near poultry farms was significantly associated with mcr-1 acquisition during domestic travel.
Diarrhea during travel was significantly associated with mcr-1 acquisition.
Acquired MCRPEC strains exhibited marked genetic diversity, comprising 10 distinct sequence types.
The mcr-1 gene was carried on multiple plasmid types, and the vast majority were transferable via conjugation.
Gut microbiome analysis showed increased alpha-diversity after travel but a stable overall community structure, indicating colonization without major disruption.
Plasmid replicon types, ARG profiles, and virulence factors were comprehensively characterized across acquired MCRPEC isolates.
This research suggests that traveling within China — not just internationally — can lead healthy people to pick up a concerning antibiotic resistance gene called mcr-1, which makes bacteria resistant to colistin, an antibiotic used as a last resort for some serious infections. In a study of 81 healthy adults who had no mcr-1 in their gut bacteria before travel, nearly 1 in 7 (14.8%) tested positive for mcr-1-carrying E. coli after their domestic trips. Two key risk factors were identified: living near poultry farms and experiencing diarrhea during the trip. The mcr-1 gene found in these travelers was carried on plasmids — mobile genetic elements that can easily jump between bacteria — and over 90% of the bacteria carrying this gene could transfer it to other bacteria in lab tests. The bacteria also carried dozens of additional antibiotic resistance genes and traits that help them stick to and infect human cells, making them potentially more dangerous if they cause an infection. Importantly, while travelers' gut microbiomes showed some changes after travel, the overall bacterial community remained largely intact, meaning the resistant bacteria quietly took up residence without causing obvious disruption. This research suggests that domestic travel within countries where antibiotic-resistant bacteria are common can be an important but underappreciated route by which these resistant bacteria spread among people. The findings highlight the need for antimicrobial resistance surveillance programs to track not just international travel but also movement within countries, and to consider the links between animal farming practices and human health — an approach known as 'One Health.'
Wu M, Chen Y, Su M, Wu H, Luo L, Ao X, et al.. (2026). Domestic travel as a driver for the dissemination of mcr-1 in healthy travelers in China: a prospective, genomic epidemiological and gut microbiome study.. Antimicrobial agents and chemotherapy. https://doi.org/10.1128/aac.01746-25