Blastocystis Subtypes and Culture Characteristics of Isolates from Human Stools Related with the Presence of Gastrointestinal Symptoms: A Case–Control Study

To stablish if Blastocystis subtypes influences gastrointestinal symptoms. Case–control study. We obtained sequencing for Blastocysts subtyping from 13 patients with gastrointestinal symptoms (diarrhea or abdominal pain) and 12 from individuals without symptoms. 12 sequences were from Subtype 2 and one from Subtype 3 in symptomatic individuals and nine samples were from Subtype 1, one from Subtype 2, and two from Subtype 3 in asymptomatic individuals. The prevalence of subtype 2 in symptomatic individuals was vastly different compared to the frequency in asymptomatic individuals (84.6% vs. 16.6%; OR 27.5 95% CI 3.2–233; Fisher exact test p = 0.0010201335). After in vitro culture, 22 isolates were obtained. Significant differences were observed for the 12 isolates from Subtype 2 that get a smaller number of total cells with dominant growth of vacuolar forms, compared with Subtypes 1 and 3, after eight days of culture. Our results suggest that gastrointestinal symptoms in Colombian individuals with Blastocystis infection depend on the infecting subtype with peculiar phenotypic characteristics in in vitro culture.