Polymerase chain reaction-based genotype classification among human Blastocystis hominis populations isolated from different countries
Since the genotype of human Blastocystis hominis isolates is highly polymorphic, PCR-based genotype classification using known sequenced-tagged site (STS) primers would allow the identification or classification of different genotypes. Five populations of human B. hominis isolates obtained from Japan, Pakistan, Bangladesh, Germany, and Thailand were subjected to genotype analysis by using seven kinds of STS primers. Ninety-nine out of 102 isolates were identified as one of the known genotypes, while one isolate from Thailand showed two distinct genotypes and two isolates from Japan were negative with all the STS primers. The most dominant genotype among four populations, except for all four isolates from Thailand, was subtype 3 and it varied from 41.7% to 92.3%. The second most common genotype among four populations was either subtype 1 (7.7–25.0%) or subtype 4 (10.0–22.9%). Subtype 2, subtype 5, and/or subtype 7 were only rarely detected among the isolates from Japan and Germany, while subtype 6 was not detected. The phylogenetic position of the two isolates which were negative with all STS primers, was inferred from the small subunit rRNA (SSU rRNA) genes with the known sequence data of 20 Blastocystis isolates. Since the two isolates were positioned in an additional clade in the phylogenetic tree, this suggested they were a new genotype. These results demonstrated that PCR-based genotype classification is a powerful tool with which to analyse genotypes of Blastocystis isolates obtained from clinical samples. In addition, two groups of the isolates from 15 symptomatic and 11 asymptomatic patients in Bangladesh were compared with the PCR-based subtype classification. Since both groups were only classified into two distinct genotypes of subtype 1 or subtype 3 and no statistically significant difference was observed between the two groups, in this study it could not be shown that the specific genotype correlated with the pathogenic potential of B. hominis.
- Galantowicz BB, Illueca MD, Levy J, Rayburn JL, Weinstock DJ (1993) Neonatal Blastocystis hominis diarrhea. Pediatr Infect Dis 12:345–347Google Scholar
- Jones WR (1946) The experimental infection of rats with Entamoeba histolytica. Ann Trop Med Parasitol 40:130Google Scholar
- Noel C, Peyronnet C, Gerbod D, Edgcomb VP, Delgado-Viscogliosi P, Sogin ML, Capron M, Viscogliosi E, Zenner L (2003) Phylogenetic analysis of Blastocystis isolates from different hosts based on the comparison of small-subunit rRNA gene sequences. Mol Biochem Parasitol 126:119–123CrossRefPubMedGoogle Scholar
- Zaman V, Khan KZ (1994) A comparison of direct microscopy with culture for the diagnosis of Blastocystis hominis. Southeast Asian J Trop Med Public Health 25:792–793Google Scholar