BackgroundTravel to tropical regions is associated with high risk of acquiring extended-spectrum beta-lactamase producing Enterobacterales (ESBL-E) that are typically cleared in less than three months following return. The conditions leading to persistent carriage that exceeds three months in some travellers require investigation.MethodsWhole genome sequencing (Illumina MiSeq) was performed on the 82 ESBL-E strains isolated upon return and one, two, three, six and twelve months later in 11 long-term (>three months) ESBL-E carriers following travel abroad.ResultsOne to 5 different ESBL-Escherichia coli strains were detected per traveller upon return, and this diminished to 1 after three months. Long-term carriage was due to the presence of the same ESBL-E. coli strain, for more than three months, in 9 out of 11 travellers (STc 10, 38, 69, 131 and 648). The mean carriage duration of strains belonging to phylogroups B2/D/F, associated with extra-intestinal virulence, was higher than those belonging to commensal-associated A/B1/E phylogroups (3.5 vs 0.5 months, p=0.021). Genes encoding iron capture systems (fyuA, irp), toxins (senB, sat), adhesins (flu, daaF, afa/nfaE, pap, ecpA) and colicin (cjrA) were more often present in persistent strains than in transient ones. Single nucleotide polymorphism (SNP) analysis in persistent strains showed a maximum divergence of 8 SNPs over 12 months without signs of adaptation.ConclusionLong-term colonization of ESBL-E following travel is due primarily to the acquisition of E. coli strains belonging to epidemic clones and harbouring “virulence genes”, allowing good adaptation to the intestinal microbiota.
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