Volume 48, Issue 3
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



The tachyzoite of the human pathogen is morphologically indistinguishable from the proliferative stages of some other zoonotic coccidia, including . To determine the identity of such coccidia obtained from human tissues and other sources, we compared riboprints (through restriction enzyme analysis of the polymerase chain reaction [PCR]-amplified small subunit rRNA gene) of the following protozoa: the RH and ts-4 strains of , lines OH3 and S11, which are two recently isolated -like parasites from Brazil, species, and the malarial parasite . In addition, the protozoan genomes were examined by PCR for homologs of surface antigen genes of , and by Southern hybridization to the heterologous rRNA gene probe pSM 389. Strains OH3, S11, ts-4, and RH shared identical riboprints, and OH3, S11, and ts-4 have p22 and p30 surface antigen gene structures similar to RH. In contrast, riboprints for and differ with respect to 1 sites, and moreover, their genomes vary significantly from one another at both the p22 and p30 gene loci. The riboprints of and differ markedly from and and from each other. HI pSM 389 restriction fragment length polymorphisms differentiate ts-4 from RH, OH3, and S11. Our results confirm that OH3 and S11 are indeed , but that and are likely to be separate species, thereby resolving previous uncertainties concerning the identity of these parasites. Together, the variation in riboprints and surface antigen gene structure reflects the phylogenetic diversity among these coccidia, and in addition, confirms the value of riboprinting in the identification of apicomplexan parasites such as .


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