RT Journal Article SR Electronic T1 Population-level analysis of Blastocystis subtype prevalence and variation in the human gut microbiota JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP gutjnl-2018-316106 DO 10.1136/gutjnl-2018-316106 A1 Raul Y Tito A1 Samuel Chaffron A1 Clara Caenepeel A1 Gipsi Lima-Mendez A1 Jun Wang A1 Sara Vieira-Silva A1 Gwen Falony A1 Falk Hildebrand A1 Youssef Darzi A1 Leen Rymenans A1 Chloë Verspecht A1 Peer Bork A1 Severine Vermeire A1 Marie Joossens A1 Jeroen Raes YR 2018 UL http://gut.bmj.com/content/early/2018/08/31/gutjnl-2018-316106.abstract AB Objective Human gut microbiome studies are mainly bacteria- and archaea-oriented, overlooking the presence of single-cell eukaryotes such as Blastocystis, an enteric stramenopiles with worldwide distribution. Here, we surveyed the prevalence and subtype variation of Blastocystis in faecal samples collected as part of the Flemish Gut Flora Project (FGFP), a Western population cohort. We assessed potential links between Blastocystis subtypes and identified microbiota–host covariates and quantified microbiota differentiation relative to subtype abundances.Design We profiled stool samples from 616 healthy individuals from the FGFP cohort as well as 107 patients with IBD using amplicon sequencing targeting the V4 variable region of the 16S rRNA and 18S rRNA genes. We evaluated associations of Blastocystis, and their subtypes, with host parameters, diversity and composition of bacterial and archaeal communities.Results Blastocystis prevalence in the non-clinical population cohort was 30% compared with 4% among Flemish patients with IBD. Within the FGFP cohort, out of 69 previously identified gut microbiota covariates, only age was associated with Blastocystis subtype carrier status. In contrast, a strong association between microbiota community composition and Blastocystis subtypes was observed, with effect sizes larger than that of host covariates. Microbial richness and diversity were linked to both Blastocystis prevalence and subtype variation. All Blastocystis subtypes detected in this cohort were found to be less prevalent in Bacteroides enterotyped samples. Interestingly, Blastocystis subtypes 3 and 4 were inversely correlated with Akkermansia, suggesting differential associations of subtypes with host health.Conclusions These results emphasise the role of Blastocystis as a common constituent of the healthy gut microbiota. We show its prevalence is reduced in patients with active IBD and demonstrate that subtype characterisation is essential for assessing the relationship between Blastocystis, microbiota profile and host health. These findings have direct clinical applications, especially in donor selection for faecal transplantation.