Blastocystis hominis found in stool specimens has been the most frequently identified parasite among foreign workers from Southeast Asia in Taiwan since 1992. The prevalence of B. hominis was 14.1% in this study. In their quarantine physical examinations, 121 male Thai workers were examined hematologically and screened for stool parasites using the merthiolate-iodineformaldehyde concentration method. Hematological values were compared in workers with and without a B. hominis infection. Multiple regressions were used to adjust for age. Those infected with any parasite other than B. hominis were excluded from further analysis. The workers infected with B. hominis had a lower leukocyte count (6.5±0.4x10 3 /ll) than those who were not (7.4±0.2x10 3 /ll). This was mainly caused by a reduced neutrophil count (3.2±0.4 vs 4.2±0.2x10 3 /ll). Hemoglobin (13.9±0.3 vs 14.5±0.1 g/dl) and hematocrit (41.4±0.6 vs 42.9±0.2%) were also reduced in B. hominis-positive workers.
Blastocystis hominis is an intestinal protozoan that is often neglected, despite causing abdominal pain and diarrhea. Previous research has demonstrated that lipids can be synthesized by B. hominis or can accumulate in growth medium, but their function and mechanisms in the pathogenesis of Blastocystis remain unclear. Our study found that lipid-rich Blastocystis ST7-B can increase inflammation and disrupt Caco-2 cells more than the same parasite without the lipovenoes supplement. Additionally, the cysteine protease of Blastocystis, a virulence factor, is upregulated and has higher activity in lipid-rich Blastocystis. In order to better understand the effects of lipids on Blastocystis pathogenesis, we treated lipid-lowering pravastatin during Blastocystis ST7-B culturing with a lipovenoes supplement, which decreased the lipid levels of the Blastocystis and reduced the Blastocystis-induced inflammation and cell disruption of Caco-2 cells. We also analyzed the fatty acid composition and possible synthesis pathway in Blastocystis ST7-B, finding significantly higher ratios of arachidonic acid, oleic acid, and palmitic acid than in the other lipid components in lipid-rich Blastocystis ST7-B. These results suggest that lipids play a significant role in the pathogenesis of Blastocystis and provide important information on the molecular mechanisms of and potential treatments for Blastocystis infection.
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