PHYLOGENETIC ANALYSIS OF CRYPTOSPORIDIUM PARASITES BASED ON THE SMALL SUBUNIT RIBOSOMAL RNA GENE FOCUS

Authors: XIAO, LIHUA - US DEPT HEALTH ATLANTA GA; ESCALANTE, LILLIAN - US DEPT HEALTH ATLANTA GA; YANG, CHUNFU - US DEPT HEALTH ATLANTA GA; SULAIMAN, IRSHAD - US DEPT HEALTH ATLANTA GA; ESCALANTE, ANANNIAS - CDC; MONTALI, RICHARD - SMITHSONIAN INST.; FAYER, RONALD; LAI, ALTAF - CDC

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Biologic data supports the concept that there are multiple species of Cryptosporidium. A recent review of web posted, unpublished and published genetic information has led a group of scientists to argue against this concept and they have concluded that only one species exists. To resolve this conflict in taxonomy which is important for identification of pathogens of animals and humans the present study was undertaken in which the small subunit ribosomal RNA genes were analyzed and 4 species were clearly identified. Species and strain specific diagnostic tools were developed that can now be used for sensitive molecular typing.

Technical Abstract: Biologic data supports the presence of multiple species in the genus Cryptosporidium, but a recent analysis of the available genetic data has concluded against that. In order to resolve the controversy in the taxonomy of this parasite, we have characterized the small subunit ribosomal RNA gene (SSU rRNA) of C. parvum. C. wrairi, C. baileyi, C. muris and C. serpentis, and uindertaken a phylogenetic analysis of the genus Cryptosporidium. Contrary to the result of a recent phylogenetic analysis, the results of our study reveal that the genus Cryptosporidium contains phylogenetically distinct species. The phylogenetic studies reveal that C. parvum, C.muris, C. baileyi and C. serpentis are distinct, which is in agreement with the biologic characteristics and host specificity. The Cryptosporidium spp. formed two clades, with C. parvum and C. baileyi belonging to one clade and C. muris and C. serpentis forming another clade. Within C. parvum, human genotype 1 and guinea pig isolate (known as C. wrairi) each difer from bovine and human genotype 2 isolates in the nucleotide sequence at four regions. C. muris bovine isolates are also different from parasites isolated from a rock hyrax and a Bactrian camel. Based on the genetic information, a species and strain specific PCR-RFLP diagnostic tool has been developed. These results clarify the phylogenetic status of the genus Cryptosporidium, and have led to the development of a specific and sensitive molecular typing tool.