I have been waiting for this study (behind the Elsevier paywall) to be published for some time. In the largest and most detailed study to date, Dutch investigators followed up 2,001 travellers and 215 of their non-travelling household members for one year, and found that 34.3% of travellers had acquired extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) during their travels (mostly for the purpose of tourism) abroad.

Unsurprisingly, antibiotic use was strongly and independently associated with acquisition of ESBL-E, and again unsurprisingly, the biggest culprit antibiotic was fluoroquinolones (i.e. ciprofloxacin, levofloxacin, etc). On average, the time taken for the ESBL-E-colonised travellers to “lose” their drug-resistant “companions” was one month, with 11.3% still positive after the full year of follow-up. What was potentially worse was that up to 7.7% of non-travelling household contacts also acquired ESBL-E subsequently – but the level of molecular testing does not permit us to conclude whether all or most had acquired their travelling household partners’ drug-resistant bacteria. The chart below, adapted from the article, shows ESBL-E acquisition by region of the world. The results are also unsurprising.

The individual countries with the highest ESBL-E acquisition per 100-person travel days were Egypt, India, Nepal, Vietnam, Peru and China. Singapore was not on the list (either numbers too low or no travellers from Holland during this period). Thailand and Malaysia were in the median range at 3.78 and 1.50 per 100-person travel days respectively.