L NAEF¹, L BERLINGER¹, E CLAAS², M ALTWEGG<sup>1

1</sup>Bioanalytica, Maihofstrasse 95a, Lucerne, Switzerland, ²LUMC, Leiden, Netherlands

Background: Conventional methods reveal established pathogens only in a minority of patients with infectious diarrhea. Amplification methods are more sensitive and more rapid and thus have a higher clinical impact. However, the question remains whether highly multiplexed assays like the FilmArrayTM Gastrointestinal Panel (22 different pathogens detected) or more targeted assays like the BD MAXTM Enteric Bacterial Panel (detecting Salmonella, Shigella/EIEC, Campylobacter and EHEC) are more adequate for routine use also in view of the significantly different reagent costs. Methods: A total of 112 stool specimens (patients >12y; no suspicion for C. difficile-related infection) were selected based on EBP-result (10 positive for Salmonella, 8 for Shigella/EIEC, 26 for Campylobacter and 9 for EHEC; 59 negatives) and travel history. All specimens were analyzed by FilmArrayTM within 24 hours. Discrepancies were resolved by in-house PCR. Results for EPEC were excluded from the analysis due to little clinical significance in adults. Results: As compared to the EBP, the FilmArrayTM had a sensitivity/specificity of 100%/99.0% for Salmonella, 100%/100% for Shigella/EIEC, 95.8%/98.8% for Campylobacter and 100%/100% for EHEC. In patients with (N=51) and without (N=61) recent travel, 21 (41%) and 30 (49%) were found positive by the EBP whereas 35 (69%) and 34 (56%) were positive with the FilmArrayTM. EAEC (18/51; 35%) and ETEC (14/51; 27%) were the most prevalent organisms in travelers, Campylobacter (20/61; 33%) in non-travelers. More than one pathogen was found with the FilmArrayTM in 3/34 (9%) positive patients without but in 20/35 (57%) with recent travel. Of these, 10, 8, 1 and 1 harbored 2, 3, 4 and 5 different pathogens, respectively. Conclusions: We conclude that the highly multiplexed FilmArrayTM detects a putative pathogen in more patients and also reveals a higher number of double or multiple infections. However, this is valid only for patients with recent travel to a developing country and not for those with locally acquired infectious diarrhea. Our results may help to select the most appropriate and cost-effective diagnostic approach based on patient selection.