ESBL-producing and colistin-resistant Enterobacterales among Czech international travellers: genomic relatedness to community and environmental isolates

Abstract

BACKGROUND: While antimicrobial resistance in Enterobacterales is closely monitored in healthcare settings, much less is known about the circulation of these bacteria in the community, particularly in high-risk groups such as travellers. This study aimed to determine the prevalence of intestinal carriage of extended-spectrum β-lactamase (ESBL)-producing, carbapenem- and colistin-resistant Enterobacterales in returning symptomatic Czech travellers, and to investigate whether travel contributes to colonisation with resistant strains distinct from those circulating in the Czech Republic. METHODS: Stool samples were cultured using a selective chromogenic medium following enrichment. Isolates with phenotypic resistance were characterised by short and long-read whole-genome sequencing. Genomes of ESBL and mcr-1-carrying E. coli isolates from travellers were compared with available genomes from various Czech sources, including wastewater treatment plants, hospital sewage, river water, patients with urinary tract infections, rectal swabs from medical students, and meat samples. RESULTS: Between September 2019 and October 2021, 165 stool samples (male=91, 55.2%, average age 41 years) were analysed. Thirty-two travellers (19.4%) were culture-positive on the ESBL screening media, with ESBL genes identified in 17.6% (29/165). The bla(CTX-M-15) gene was dominant (59%, 17/29), located either on the plasmid or the chromosome. Three non-ESBL E. coli isolates carried the mcr-1 gene (1.8%, 3/165). No carbapenem-resistant isolates were recovered. No clonal relatedness was observed between ESBL-carrying E. coli isolates or their plasmids from travellers and other sources. CONCLUSION: Czech travellers frequently carried diverse ESBL-producing Enterobacterales, suggesting that travel contributes to the dissemination of bacterial strains and mobile genetic elements harbouring antimicrobial resistance genes.