Introduction

Gut pathogens play a relevant role in shaping the natural history of noncommunicable chronic gastrointestinal (GI) disorders, as they are not only a risk factor for the development of irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD)^1,2, but can also trigger a clinical relapse of these conditions². Molecular testing for quick pathogen detection have been made available in recent years, but their sensitivity may result in clinically insignificant positive findings, as gut pathogens may be present, at low counts, also in clinically healthy individuals³. Their use is also recommended in stool donor screening flowchart to minimize the risk of transmission of infectious diseases during fecal microbiota transplantation (FMT).

Aims & Methods

Our aim was to evaluate whether the presence of gut pathogens, assessed by a direct molecular stool testing, differs in different GI disorders and healthy individuals. In this retrospective study, we evaluated the results of a commercially available, RT-PCR-based molecular stool testing for the detection and identification of 25 common gut pathogens (RT-PCR Allplex™ Gastrointestinal Panel Assays, Seegene, Seoul, Korea) in three different cohorts, including: patients with IBD; patients with IBS; candidate stool donors of our FMT centre. Testing were required when common microbiological stool testing (i.e. stool culture, C. difficile toxin, parasitological assays) were negative. We collected the following data of recruited individuals: age, gender, presence of GI symptoms (assessed with the GSRS) and disease activity (assessed with PMS, HBI).

Results

Overall, 403 stool tests were retrospectively analyzed. Of them, 177 came from 46 healthy donors (n= 89 tests of females, mean age 44; range: 21-69; SD 12.5); 183 from 146 patients with IBD (n=100 tests of females, mean age 40.4; range: 16-82; SD 16.2), and 27 from 26 patients with IBS (n= 12 tests of females, mean age 39; range: 16-68; SD 17.1). Among healthy donors, 60 (34%) tests were positive, 15 (8%) for multiple species. Enteropathogenic Escherichia coli (EPEC) was the most frequently isolated strain (n=23; 13%). In the IBD cohort, 155 tests were collected in patients with active disease, and among them 59 (38%) tests turned out to be positive, 18 (12%) for multiple species, with EPEC being the most common strain (n=15; 10%), followed by Aeromonas spp (n=13; 8%), Blastocystis hominis (n=11; 7%) and Clostridium difficile (n= 10; 6%). In this cohort, 28 tests were also requested to patients under quiescent disease, and 10 (36%) were positive. In patients with IBS, all tests were conducted during active, symptomatic phases of disease (IBS-D: n=19, 68%; IBS-C: n=8; 30%), with 13 (48%) positive testing, mainly due to Blastocystis hominis (n=5; 19%), followed by Dientamoeba (n=3; 11%), and by multiple species in 11% of patients (n=3).

Conclusion

In our cohort, the positivity rates of gut pathogens at direct molecular stool testing were similar among healthy donors (34%), patients with active (38%) and quiescent (36%) IBD, being slightly higher in patients with active IBS (48%). Based on these preliminary finding, direct molecular stool testing, in absence of positive stool cultures, is associated with asymptomatic colonization from gut pathogens, rather than with clinically relevant infections, both in healthy controls and in patients with noncommunicable chronic GI disorders.

References

(1) Lupu, V. V.; Ghiciuc, C. M.; Stefanescu, G.; Mihai, C. M.; Popp, A.; Sasaran, M. O.; Bozomitu, L.; Starcea, I. M.; Adam Raileanu, A.; Lupu, A. Emerging Role of the Gut Microbiome in Post-Infectious Irritable Bowel Syndrome: A Literature Review. World J Gastroenterol 2023, 29 (21), 3241–3256. https://doi.org/10.3748/wjg.v29.i21.3241.
(2) Axelrad, J. E.; Joelson, A.; Green, P. H. R.; Lawlor, G.; Lichtiger, S.; Cadwell, K.; Lebwohl, B. Enteric Infections Are Common in Patients with Flares of Inflammatory Bowel Disease. Am J Gastroenterol 2018, 113 (10), 1530–1539. https://doi.org/10.1038/s41395-018-0211-8.
(3) Rondinella, D.; Quaranta, G.; Rozera, T.; Dargenio, P.; Fancello, G.; Venturini, I.; Guarnaccia, A.; Porcari, S.; Bibbò, S.; Sanguinetti, M.; Gasbarrini, A.; Masucci, L.; Cammarota, G.; Ianiro, G. Donor Screening for Fecal Microbiota Transplantation with a Direct Stool Testing-Based Strategy: A Prospective Cohort Study. Microbes and Infection 2024, 105341. https://doi.org/10.1016/j.micinf.2024.105341.

Disclosure

G.I. has received personal fees for acting as speaker for Biocodex, Danone, Sofar, Malesci, Metagenics and Tillotts Pharma, and for acting as consultant and/or advisor for Ferring Therapeutics, Giuliani, Malesci and Tillotts Pharma. A.G. reports personal fees for consultancy from Eisai Srl, 3PSolutions, Real Time Meeting, Fondazione Istituto Danone, SinergieSrl, Board MRGE and Sanofi SpA personal fees for acting as a speaker for Takeda SpA, AbbVie and Sandoz SpA and personal fees for acting on advisory boards for VSL3 and Eisai. G.C. has received personal fees for acting as advisor for Ferring Therapeutics. All other authors have no
conflicts of interest to disclose.