Authors

T P Jenkins⁴; F Formenti¹; C Piubelli¹; C Castro²; F Perandin¹; D Buonfrate¹; J Griffin²; D Otranto³; Z Bisoffi¹; C Cantacessi⁴;  ¹ Centre for Tropical Diseases, Sacro Cuore-Don Calabria Hospital, Negrar, Verona, Italy;  ² Department of Biochemistry, Metabolomics Facility, University of Cambridge, UK;  ³ Department of Veterinary Medicine, University of Bari, Valenzano, Italy;  ⁴ Department of Veterinary Medicine, University of Cambridge, UK

Discussion

Data from recent studies support the hypothesis that infections by human gastrointestinal (GI) helminths impact, directly and/or indirectly, on the composition of the host gut microbial flora. However, to the best of our knowledge, these studies have been conducted in cohorts of human volunteers from helminth-endemic areas and infected by multiple species of parasites or with underlying gut disorders, which, in most cases, impaired an unbiased assessment of the sole effects of GI parasites on the gut microbial profiles. Exploring the impact that single species of GI helminths exert on the gut microbial composition of otherwise healthy human volunteers may help disentangle the causality of parasite-microbiota relationships. Thus, in this study, we explored the impact of natural infections by the parasitic nematode Strongyloides stercoralis on the gut microbiota and the metabolic profiles of a cohort of otherwise healthy individuals from northern Italy, pre- (S+) and post- (St) anthelmintic treatment with ivermectin and compared the findings with data obtained from a cohort of uninfected individuals (S-) from the same geographical area.
Bioinformatics and biostatistical analyses of bacterial 16S rRNA gene data revealed a significantly increased microbial alpha diversity (P ≤ 0.03) and decreased beta diversity (P ≤ 0.04) in the gut microbial profiles of S+ subjects compared to S-. In St subjects, gut microbial alpha diversity was higher than in S- and lower than in S+ subjects, while beta diversity was lower than in S- and higher than in S+ subjects, albeit not significantly. Amongst others, populations of bacteria belonging to the Order Pseudomonadales (genus Pseudomonas) and genus Bacteroides were significantly more abundant in the microbiota of S- subjects compared to both S+ and St subjects. Conversely, Leuconostocaceae, Paraprevotellaceae and Peptococcus were significantly increased in the microbiota from S+ subjects compared to S-. The gut microbiota of St was characterized by a higher abundance of Lachnobacterium and Roseburia compared to S-, and of bacteria of the order Enterobacteriales compared to S+ subjects. Metabolomic analysis using nuclear magnetic resonance (NMR) and gas chromatography revealed significant differences in the abundance of selected faecal metabolites between subject groups. For instance, levels of acetate were significantly higher in the faecal metabolome of S- compared to S+ subjects (P ≤ 0.03), whilst those of alanine, formate and leucine were higher in S+ compared to S- subjects (P ≤ 0.05, P ≤ 0.03 and P ≤ 0.05, respectively). The saturated fatty acid C15:0 ante (pentadecanoic acid) was significantly increased in faecal samples from St compared to S+ subjects (P ≤ 0.02).