| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 106 === Blastocystis hominis (B. hominis) is one of the most common intestinal protozoan parasites in humans. Pathogenicity of B. hominis remains controversial and it has been suggested that it may be associated with certain subtypes of organism. Based on the genetic diversity of SSU rRNA (small subunit ribosomal RNA gene, SSU rRNA), B. hominis can be classified into 17 subtypes. From the results of stool samples for parasite test from the regional hospital in southern Taiwan, it was demonstrated that B hominis had the highest prevalence rate (90.2%) of intestinal parasites. The infection rate of B. hominis in foreign population was significantly higher than that of nationals (14.7% vs 4.2%). The aims of this study were to set up nested polymerase chain reaction (nested PCR) for DNA amplification and subtyping. The results were shown 81 of 112 specimens positive for B. hominis and 18 of 200 specimens negative for microscopy were shown positive by nested PCR detection. The sensitivity and the specificity of the nested PCR molecular detection method were 72.3% and 91%; respectively. Our results revealed the positive detection rate increased 9% by nested PCR compared with by microscopy. We hoped that this technology can be applied in the clinical laboratory for B. hominis screening. The sequences of 99 PCR positive samples were analyzed. The most common subtypes were ST3 (44.4%, 44/99), ST1 (43.4%, 43/99), followed by ST2 (5.1 %, 5/99), ST6 (4.0%, 4/99) and ST7 (3.0%, 3/99). A phylogenetic tree was reconstructed using the neighbor-joining method based on the Kimura-2-Parameter model and it was found that five subtypes (ST1, ST2, ST3, ST6 and ST7) can be regarded as five independent monophyletic groups. By phylogenetic analysis, Bh97 and ST1 (AB107961, host: pig), Bh149 and ST3 (AB107965, host: cattle) were highly correlated. It can be inferred that human Blastocysts is transmitted by humans and the possibility of common infections between humans and animals. Although the current prevalence of B. hominis in Taiwanese is lower than that of foreign workers, there is still the possibility of mutual infection through fecal-oral route. In this study, we found the subtype distribution of B. hominis were very similar between Taiwan population and Indonesians. Therefore, the foreign workers should be conducted appropriate health education to reduce B. hominis transmission and dissemination.
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