Prevalence and characteristics of 11 potentially diarrhoeagenic microbes in asymptomatic individuals in Norway, 2015–2020

We aimed to estimate the prevalence of potentially diarrhoeagenic microbes (PDMs) in faecal samples from asymptomatic individuals in a high-income country, identify risk factors for carriage and to identify microbial factors that differ between PDMs in asymptomatic versus symptomatic individuals. Samples from 1000 asymptomatic participants were collected, together with a questionnaire, between 2015 and 2020 and examined by PCR for 11 PDMs. Isolates were characterised and potential risk factors were registered. Atypical enteropathogenic Escherichia coli (aEPEC), Yersinia enterocolitica, Shiga toxin-producing E. coli (STEC), enterotoxigenic E. coli (ETEC) and Campylobacter spp. were found in 163 (16%), 20 (2.0%), 17 (1.7%), 12 (1.2%) and 11 (1.1%) asymptomatic individuals, respectively. Other PDMs were rare. Only low virulent STEC, with stx1c, stx2b or stx2f, was detected. Travels outside Europe was a significant risk factor for detecting Campylobacter spp. (odds ratio (OR) 6.99; 95% CI 1.12–43.6) and ETEC (OR 11.4; 95% CI 1.26–102). Individuals ≥65 years of age had lower odds of carrying STEC (OR 0.11; 95% CI 0.02–0.57) or EPEC (OR 0.09; 95% CI 0.05–0.16) than individuals ≤5 years of age. The common finding of PDMs in asymptomatic individuals could have implications for the interpretation of positive findings in clinical samples and infection control measures.