Objectives: Prospectively study the influence of foreign travel and associated risk factors on the acquisition of AMR in the endogenous microbiota of healthy individuals and the subsequent persistence of AMR carriage and transmission to household members of these carriers. Examine whether carriers of resistant Enterobacteriaceae have a higher risk of bacterial infections in the year after travel (compared to non-carriers). Explore the full width of AMR genes and transferable genetic elements acquired during international travel.

Rationale: Antimicrobial resistance (AMR) among Enterobacteriaceae constitutes an increasingly important human health hazard worldwide. Also in the Netherlands AMR rates have been on the rise in recent years. A limited number of previous studies have suggested high acquisition rates of AMR E. coli during international travel, but information on travel-associated risk factors, duration of colonization and local transmission of imported AMR are largely, if not entirely, lacking.

Objectives: Prospectively study the influence of foreign travel and associated risk factors on the acquisition of AMR in the endogenous microbiota of healthy individuals and the subsequent persistence of AMR carriage and transmission to household members of these carriers. Examine whether carriers of resistant Enterobacteriaceae have a higher risk of bacterial infections in the year after travel (compared to non-carriers). Explore the full width of AMR genes and transferable genetic elements acquired during international travel.

Study design: multicenter longitudinal cohort study.

Study population: healthy, adult (> 18 years) volunteers travelling abroad for 1 week - 3 months. Non travelling household members of these traveling volunteers.

Methods: Travelers and non-traveling household members will be recruited at outpatient travel clinics throughout The Netherlands. Faecal samples and questionnaires will be taken before (t=0) travel, immediately after travel (t=1) and 1 month upon return (t = 2). For volunteers that acquire AMR Enterobacteriaceae, repeated questionnaires and faecal samples will be taken after 3, 6 and 12 months.

Faecal samples will be cultured to screen for AMR Enterobacteriaceae. Suspected colonies will be identified and susceptibilities confirmed by standard methods. Genotypic characterization of the extended-spectrum betalactamase- (ESBL-) and carbapenemase genes will be performed using microarray and gene sequencing. Clonal bacterial spread within households will be confirmed or excluded by molecular typing.

Outcomes: The main outcome measure is the acquisition rate and persistence of AMR in the endogenous microbiota of healthy travelers upon travel.

Secondary outcomes are the duration of colonization, the rate of secondary transmission within households, the identification of risk factors, occurrence of self-reported infections in the year following travel and the abundance and type of resistance.

Inclusion Criteria:

• age > 18 years
• travelling for > 1 week (7 days) AND < 3 months (90 days)
• non traveling household members of these traveling volunteers

Travelers and their family members not planning to travel