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

Purpose: To stablish if Blastocystis subtypes influences gastrointestinal symptoms.

Methods: 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.

Results: 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.

Conclusion: 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.