Research in context
Evidence before this study
We searched PubMed on Aug 17, 2015, with the search terms “Gram negative bacteria”, “Enterobacteriaceae”, “Escherichia”, ”Klebsiella”, ”Salmonella”, “Shigella”, “Yersinia”, “travel”, “tourist”, “tourism”, “turista”, “aviation”, “air transport”, “airport”, “resistance”, “colonisation”, “antibiotic”, “susceptibility”, “carriage”, and “carrier”. We did a systematic review and identified 11 eligible studies. We updated this search on April 14, 2016, and found no new prospective studies. The results of the 11 prospective cohort studies showed high acquisition rates of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) among travellers who had returned from southern Asia and northern Africa. Four travellers who visited India acquired carbapenemase-producing Enterobacteriaceae (CPE). However, whether antibiotic use and traveller's diarrhoea are predictors for ESBL-E acquisition was unclear. Moreover, these studies did not sufficiently address duration of ESBL-E carriage among travellers or onward transmission within households. One study asked travellers to provide stool samples up to 12 months after return, but duration of carriage was defined by ESBL phenotype. One other study looked at household transmission, but because only 11 household contacts were included, no reliable conclusion could be inferred about the risk of household transmission.
Added value of this study
In this large-scale, longitudinal cohort study, we followed up travellers and their non-travelling household members for up to 12 months after travel. The large sample size meant that we could investigate ESBL-E acquisition among travellers who had returned from a large number of countries across the world, including those such as Uganda, for which community carriage rates of ESBL-E were previously unknown. We identified several predictors (some new) for ESBL-E acquisition, including factors specific to subregions. Moreover, we were able to ascertain duration of ESBL-E carriage and associated resistance genes, identify predictors for sustained colonisation, and to model transmission rates mathematically within households.
Implications of all the available evidence
High frequencies of ESBL-E acquisition during travel, subsequent sustained carriage, and evidence of onward transmission within households show that travellers contribute to the emergence and spread of ESBL-E on a global scale. Active screening for ESBL-E and CPE and adjustment of empirical antimicrobial therapy should be considered for returning travellers at increased risk of ESBL-E carriage. However, implications for infection prevention and antibiotic treatment policies will differ locally because the degree of consequence of acquisition and spread of ESBL-E by travellers is highly dependent on local ESBL-E prevalence in the country of origin.