Intra-isolate variation of Cryptosporidium parvum small subunit ribosomal RNA genes from human hosts in England

Abstract

Cryptosporidium parvum is a protozoan parasite responsible for a number of water-borne outbreaks of human gastrointestinal infection. The importance of this parasite for human health has led to several investigations into its epidemiology. In the present study, sequence and PCR-RFLP analyses were performed on cloned SSU rRNA genes from human and bovine C. parvum isolates. Each cloned gene was assigned a genotype using AseI restriction digestion profiles. Although sequence heterogeneity was observed, six of seven human isolates contained human genotype SSU rRNA genes and one human isolate contained bovine genotype genes. No intra-isolate variation was observed between the SSU rRNA genes analysed from a single bovine (Iowa) isolate. Intra-isolate variation did not occur at the Ase I restriction sites and therefore did not interfere with the assignment of C. parvum genotypes by RFLP. Mixed RFLP genotypes (human and bovine) were not observed in any of the C. parvum isolates analysed.

Genetic Diversity of Cryptosporidium spp. within a Remote Population of Soay Sheep on St. Kilda Islands, Scotland

“…Cryptosporidium parvum has been documented in domestic sheep (7), and Cryptosporidium species, presumed to be C. parvum, have been identified in Soay sheep by microscopic examination using modified ZiehlNeelsen staining (13). C. parvum sequence heterogeneity is known to exist (46,47), and variability was observed in all the St. Kilda locus 1 amplicons (46). This finding is similar to that from a study of lambs within an isolated geographical area in Spain (47).…”

90-Kilodalton Heat Shock Protein, Hsp90, as a Target for Genotyping Cryptosporidium spp. Known To Infect Humans

“…Unlike the SSU rRNA gene, which sometimes has intraspecific or intragenotypic variations in RFLP patterns due to sequence variations among different copies of the gene (8,25,26), the consistent hsp90 RFLP pattern for each Cryptosporidium species/genotype facilitates molecular typing. In addition, the greater sequence heterogeneity within the Cryptosporidium Hsp90 gene than observed for SSU rRNA gene indicates that hsp90 may be a more robust tool for genotyping.…”

“…Therefore, other gene targets were analyzed for applicability. One disadvantage of the SSU rRNA gene is that there are minor sequence differences among different copies of the gene, which sometimes can lead to variation in RFLP for certain Cryptosporidium species or genotypes (8,25). In such situations, it is very important to differentiate intragenotypic variations among isolates from sequence variations between different copies of the gene (2) and to have a tool that confirms the genotype.…”

Cryptosporidium hominisInfection of the Human Respiratory Tract

“…DQ286403) is that of C. hominis , with a stretch of 11 Ts (Table). Few other nucleotide polymorphisms were found between the sequences (results not shown), which reflect intraisolate variations ( 14 ). The results with Lib13 assay and the partial 18S rRNA sequence analysis, therefore, identify the species of Cryptosporidium infecting the respiratory tract of this patient as C. hominis .…”