Predominance of subtype 3 among Blastocystis isolates from a major hospital in Singapore.

Blastocystis is an enteric protozoan parasite commonly found in humans and animals. Phylogenetic and genotypic analyses have shown that Blastocystis exhibits extreme genetic diversity, and humans are host to a number of zoonotic isolates. In the present study, the prevalence of Blastocystis in 276 stool samples from a hospital in Singapore was examined, and for the first time, riboprinting using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to determine the genetic diversity of the Blastocystis isolated from the Singapore population. The prevalence rate was determined to be 3.3% (9/276), and Blastocystis displaying two main ribotypes were isolated. As a comparison, we performed PCR-RFLP using two different published methodologies, and both methods allowed the isolates to be divided into two distinct groups based on their riboprint patterns. According to a recently proposed classification scheme, 78% (7/9) of the isolates were of subtype 3, while 22% (2/9) were subtype 1. The predominance of subtype 3 in an urbanized city state such as Singapore is in agreement with the idea that subtype 3 is a genotype of human origin.