Colonization of returning travelers with CTX-M-producing Escherichia coli

Abstract

Background: We previously identified foreign travel as a risk factor for acquiring infections due to CTX-M (active on cefotaxime first isolated in Munich) producing Escherichia coli. The objective of this study was to assess the prevalence of extended-spectrum β-lactamase (ESBL)-producing E coli among stool samples submitted from travelers as compared to non-travelers (a non-traveler had not been outside of Canada for at least 6 months before submitting a stool specimen).

Methods: Once a travel case was identified, the next stool from a non-traveler (not been outside of Canada for at least 6 months) was included and cultured on the chromID-ESBL selection media. Molecular characterization was done using polymerase chain reaction and sequencing for bla(CTX-Ms), bla(TEMs), bla(SHVs), plasmid-mediated quinolone-resistant determinants, O25-ST131, phylogenetic groups, pulsed-field gel electrophoresis (PFGE), and multilocus sequencing typing.

Results: A total of 226 individuals were included; 195 (86%) were negative, and 31 (14%) were positive for ESBL-producing E coli. Notably, travelers were 5.2 (95% CI 2.1-31.1) times more likely than non-travelers to have an ESBL-producing E coli cultured from their stool. The highest rates of ESBL positivity were associated with travel to Africa or the Indian subcontinent. Among the 31 ESBL-producing E coli isolated, 22 produced CTX-M-15, 8 produced CTX-M-14, 1 produced CTX-M-8, 12 were positive for aac(6')-Ib-cr, and 8 belonged to clone ST131.

Conclusions: Our study confirms that foreign travel, especially to the Indian subcontinent and Africa, represents a major risk for rectal colonization with CTX-M-producing E coli and contributed to the Worldwide spread of these bacteria.