ABSTRACT The global spread of plasmid-mediated colistin resistance gene mcr-1 poses a significant threat to public health. Although international travel is a known driver of antimicrobial resistance, the role of domestic travel in high-prevalence settings remains unclear. We conducted a prospective cohort study of 81 healthy volunteers traveling in China (June–September 2022). Fecal samples collected before and after travel were screened for mcr-1 -positive Escherichia coli (MCRPEC). Antimicrobial resistance genes (ARGs), virulence factors (VFs), plasmid replicons, and gut microbial dynamics were investigated using whole-genome sequencing and 16S rRNA sequencing. Risk factors were analyzed using logistic regression analysis. Of the 81 participants who were negative for mcr-1 at baseline, 12 (14.8%) acquired mcr-1 after travel. Acquisition was associated with residence near poultry farms (odds ratio OR = 5.9, P = 0.04) and diarrhea during travel (OR = 11.22, P = 0.027). MCRPEC exhibited marked genetic diversity comprising 10 sequence types and the carriage of additional 23 ARGs and nine adherence-associated VFs. mcr-1 was located on IncI2, IncX4, IncHI2, or IncP plasmids, with 91.7% ( n = 11) transferable in conjugation assays. Gut microbiome analysis showed increased α -diversity, but a stable community structure, indicating colonization without major disruption. Our study demonstrated that domestic travel in China substantially contributes to the dissemination of mcr-1 . Poultry exposure and gastrointestinal disturbances are key risk factors. Genetic diversity, plasmid transferability, and co-carriage of resistance and virulence determinants highlight the risk of onward spread. Antimicrobial resistance surveillance should extend beyond international travel and incorporate domestic mobility within a “One Health” framework.
Wu et al. (Mon,) studied this question.