title: Prolonged carriage of resistant E. coli by returned travellers: clonality, risk factors and bacterial characteristics.
abstract: The aim of this study was to delineate the potential risks and dynamics of the prolonged carriage of resistant E. coli in returned travellers. A sample of 274 previously collected E. coli resistant to ceftriaxone (CRO), ciprofloxacin, gentamicin and/or nalidixic acid recovered from 102 travellers was studied. Travellers were assessed pre-travel then longitudinally (maximum 6 months) with peri-rectal/rectal swabs. Clonality was determined by REP-PCR and the presence of O25b-ST131 was assessed. Comparison was made longitudinally for individuals and between identified co-travellers. The risk of prolonged carriage was lower for CRO than for ciprofloxacin or gentamicin resistance. Repeated isolation of the same phenotype at different time points occurred in 19% of initial CRO-resistant carriers compared with 50% of ciprofloxacin- or gentamicin-resistant carriers. The duration of carriage was also longer for the latter resistance phenotypes (75th quartile 8 vs 62 and 63 days respectively). In multivariate analysis, risks of prolonged carriage included antimicrobial use whilst travelling (3.3, 1.3-8.4) and phylogenetic group B2 (9.3, 3.4-25.6) and D (3.8, 1.6-8.8). Clonality amongst longitudinal isolates from the same participant was demonstrated in 92% of participants who were assessable and most marked amongst CRO-resistant isolates. ST-131 was surprisingly infrequent (3% of participants). Prolonged carriage of ciprofloxacin- and gentamicin-resistant isolates is more frequent and prolonged than CRO resistance after travel. Risks of prolonged carriage indicate a contribution of host and bacterial factors to this carriage. These require further elucidation. The strong clonality identified suggests that carriage of a "phenotype" was mediated by persistence of bacteria/plasmid combinations rather than persistence of the plasmid after horizontal transfer to other bacteria.
authors.affiliation: UQ Centre for Clinical Research, University of Queensland, Royal Brisbane and Women's Hospital Campus, Building 71/918, Herston, Brisbane, Queensland, Australia, 4006. benrogers@uq.edu.au
authors.forename: B A
authors.initials: BA
authors.lastname: Rogers
authors.forename: K J
authors.initials: KJ
authors.lastname: Kennedy
authors.forename: H E
authors.initials: HE
authors.lastname: Sidjabat
authors.forename: M
authors.initials: M
authors.lastname: Jones
authors.forename: P
authors.initials: P
authors.lastname: Collignon
authors.forename: D L
authors.initials: DL
authors.lastname: Paterson
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology*; D005260:Female; D005838:Genotype; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D058889:Molecular Typing; D012307:Risk Factors; D013997:Time Factors; D014195:Travel; D057236:Travel Medicine
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial