TaqMan Array Card testing of participant-collected stool smears to determine the pathogen-specific epidemiology of travellers’ diarrhoea†

BACKGROUND We assessed the compliance with self-collection of stool smears on Whatman® FTA® Elute Card (FTA Card) and detection of travelers' diarrhea (TD) associated pathogens using a quantitative PCR assay (customized TaqMan® array card [TAC]), in a prospective, observational cohort of travelers. METHODS Enrolled travelers documented symptoms on a travel diary and collected an FTA Card during a diarrheal episode, or at the end of travel if they remained asymptomatic. TAC testing was performed on FTA Cards from TD cases and 1:1 matched asymptomatic controls and 1:1 matched loose stool cases that did not meet TD criteria. Odds ratios (OR) were used to determine the association between detected pathogens and TD. RESULTS 484 of 2456 (19.7%) travelers completed an illness diary and met TD criteria, and 257 (53.1%) collected an FTA Card during the TD episode. FTA Cards were stored for a median of 2 years at room temperature (IQR: 1-4 years) before extraction and testing. The overall TAC detection rate in TD cases was 58.8% (95%CI: 52.5-64.8). Enterotoxigenic E. coli was the most common pathogen in TD cases (26.8%) and 3.5% of samples were positive for norovirus. The odds of detecting TD-associated pathogens in 231 matched cases and asymptomatic controls was 5.4 (95% CI: 3.6-8.1) and 2.0 (95% CI:1.1-3.7) in 121 matched TD and loose stool cases (p < 0.05). Enteroaggregative E coli was the most common pathogen detected in asymptomatic controls and loose stool cases. Detection of diarrheagenic E coli, Shigella/enteroinvasive E coli (EIEC), and Campylobacter spp. was significantly associated with TD. CONCLUSIONS FTA Cards are a useful adjunct to traditional stool collection methods for evaluating the pathogen-specific epidemiology of TD in austere environments. Qualitative detection of pathogens was associated with TD. Measures to improve compliance and quality of FTA Card collection with decreased storage duration may further optimize detection.