Dientamoeba fragilis (D fragilis) carriers have greater gut microbiota alpha diversity compared with noncarriers, according to a study in the Journal of Pediatric Gastroenterology and Nutrition.

Investigators sought to compare the gut microbiota composition of children with and without D fragilis colonization and assess the impact of metronidazole vs placebo on gut microbiota diversity and composition in D fragilis carriers.

Fecal samples from 96 children (49 girls) who were D fragilis-positive at baseline were available for stool microbiota analysis; 48 children were treated with metronidazole (MG group) (median age 7 years; interquartile range [IQR], 6-9 years), and 48 received placebo (PG group) (median age 6 years; IQR, 5-8 years). In addition, 70 fecal samples were included from a control group (CG group) (median age 7 years; IQR, 5-10 years) of age-matched children (41 girls) who had tested negative for D fragilis.

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The researchers found that stool alpha diversity of the D fragilis-positive children was greater than that of the children who were D fragilis-negative (P =.031). The investigators also identified 24 bacteria genera that differed significantly in abundance between the children who were colonized with D fragilis (MG and PG) and those who were not (CG).

Among children who were D fragilis-positive, the study authors observed a significantly higher abundance of 16 genera, with Victivallis and Oscillibacter especially more common in D fragilis-positive children. In addition, 8 genera were significantly more abundant in D fragilis-negative children, with Flavonifractor being significantly more abundant in noncarriers.

Among other findings, 7 of the 8 bacterial genera that changed in abundance from before treatment (T1) to 2 weeks after treatment (T2) reverted to T1 levels at 8 weeks after treatment (T5). However, Flavonifractor remained significantly more abundant at T5 in children who had lost D fragilis at T2 compared with children who had retained D fragilis at T2 (P <.01). Additionally, the increased abundance of Ruminococcus that was observed at T2 remained at T5.

The researchers also found microbiota changes specifically linked to metronidazole exposure that did not rely on D fragilis colonization. Hungatella, Streptococcus, and Sutterella were more frequent after metronidazole treatment and were not affected by D fragilis carrier status.

Among several study limitations, the investigators noted that in the PG cohort, 4 children lost D fragilis between T1 and T2, and there were too few individuals in this group to compare gut microbiota changes with the other groups. Additionally, including age- and sex-matched children with D fragilis infection but without symptoms could have provided further information on associations between the parasites and gut microbiota. Finally, the researchers studied the microbiota at the genus level and may have gained more detailed and useful information by examining some of the genera at the species level.

“Conclusively, we confirmed relatively high microbial alpha diversity in D fragilis-positive compared with D fragilis-negative children, which could support the hypothesis that D fragilis is a common organism found in gut-healthy children in Denmark and not particularly related to intestinal disease,” stated the study authors. They concluded, “Observations on up- and down-regulation of intestinal bacteria and D fragilis in relationship with drug exposure and other environmental factors may inform studies aiming to investigate ways to manipulate gut microbiota with therapeutic intent.”


Gotfred-Rasmussen H, Stensvold CR, Ingham AC, et al. Impact of metronidazole treatment and Dientamoeba Fragilis colonization on gut microbiota diversity. J Pediatr Gastroenterol Nutr. 2021;73(1):23-29. doi: 10.1097/MPG.0000000000003096

This article originally appeared on Gastroenterology Advisor