Insights Into Global Antimicrobial Resistance Dynamics Through the Sequencing of Enteric Bacteria From US International Travelers.

Background: Antimicrobial resistance (AMR) is an urgent threat to public health, but gaps in surveillance limit the detection of emergent novel threats and knowledge about the global distribution of AMR genes. International travelers frequently acquire AMR organisms (AMROs) and thus may provide a window into AMR dynamics in otherwise poorly monitored regions and environments.

Methods: To assess the utility of travelers as global AMR sentinels, we collected pre- and post-travel stool samples from 608 travelers between 2017 and 2019, which were screened for the presence of extended-spectrum beta-lactamase producing Enterobacterales, carbapenem-resistant Enterobacterales, and mcr-mediated colistin-resistant Enterobacterales. A total of 307 distinct AMROs were sequenced and analyzed in order to determine genotypic patterns and their association with geography and traveler behavior.

Results: Travel-associated AMROs were overwhelmingly Escherichia coli, which exhibited considerable phylogenetic diversity regardless of travel region. However, the prevalence of resistance genes varied by region, with blaCTX-M-55 and blaCTX-M-27 significantly more common in isolates associated with South America and South-Eastern Asia, respectively. Plasmid reconstruction revealed the genomic neighborhood of blaCTX-M-55 frequently matched a motif previously linked to animal populations. The ColV plasmid, a driver of avian pathogenic E. coli, was found to be elevated in frequency in isolates acquired by travelers reporting animal contact. We identified novel variants of the mcr-1 gene in strains acquired from Western Africa.

Conclusions: Traveler pathogen genomic surveillance can provide insight on global AMR dynamics and emerging clinical threats. Ongoing efforts to track travel-acquired organisms could complement existing global AMR surveillance frameworks.