Five subgroups of Blastocystis hominis from symptomatic and asymptomatic patients revealed by restriction site analysis of PCR-amplified 16S-like rDNA.

DNA polymorphism of Blastocystis hominis isolates was examined by the amplification of a gene fragment coding for the 16S-like rDNA. Using identical primers, fragments of approximately 850 bp were amplified from 110 B. hominis isolates and fragments of 1.1 kbp were amplified from 48 isolates. Digestion of the amplification products with the restriction enzymes HinfI, RsaI, and AluI revealed different profiles for each fragment length. Subgroup I and II, resulting from digestion of the smaller 850 bp fragment, have identical HinfI and AluI restriction bands, subgroup III and IV have identical RsaI fragments after digestion of the 1.1 kbp DNA. Subgroup V resembles subgroup III in a few bands after the RsaI and AluI restriction, respectively. Ninety (54%) of the isolates studied were assigned to subgroup I, 20 (12%) to subgroup II, 35 (21%) to subgroup III, 12 (7%) to subgroup IV, and 1 (1%) to subgroup V. Five (3%) of the examined people were coinfected with B. hominis of the subgroup III, 3 (2%) carried B. hominis of the subgroup I and II. These results show that there are 5 B. hominis subgroups none of which was found to be significantly correlated with the reported disease.