Genetic diversity within Cryptosporidium parvum and related Cryptosporidium species - PubMed (original) (raw)

Comparative Study

L Xiao et al. Appl Environ Microbiol. 1999 Aug.

Abstract

To assess the genetic diversity in Cryptosporidium parvum, we have sequenced the small subunit (SSU) rRNA gene of seven Cryptosporidium spp., various isolates of C. parvum from eight hosts, and a Cryptosporidium isolate from a desert monitor. Phylogenetic analysis of the SSU rRNA sequences confirmed the multispecies nature of the genus Cryptosporidium, with at least four distinct species (C. parvum, C. baileyi, C. muris, and C. serpentis). Other species previously defined by biologic characteristics, including C. wrairi, C. meleagridis, and C. felis, and the desert monitor isolate, clustered together or within C. parvum. Extensive genetic diversities were present among C. parvum isolates from humans, calves, pigs, dogs, mice, ferrets, marsupials, and a monkey. In general, specific genotypes were associated with specific host species. A PCR-restriction fragment length polymorphism technique previously developed by us could differentiate most Cryptosporidium spp. and C. parvum genotypes, but sequence analysis of the PCR product was needed to differentiate C. wrairi and C. meleagridis from some of the C. parvum genotypes. These results indicate a need for revision in the taxonomy and assessment of the zoonotic potential of some animal C. parvum isolates.

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Figures

FIG. 1

FIG. 1

Phylogenetic relationship of Cryptosporidium parasites within the broad C. parvum group by neighbor-joining (A) and parsimony (B) analyses. Bootstrap values above 50% from 1,000 pseudoreplicates are also shown.

FIG. 2

FIG. 2

Genotyping of the C. parvum group parasites by a nested PCR-RFLP procedure based on the SSU rRNA gene sequences. Lanes 1 and 15, molecular size markers; lane 2, C. parvum human genotype; lane 3, C. parvum monkey genotype; lane 4, C. parvum bovine genotype, A gene; lane 5, C. parvum bovine genotype, B gene; lane 6, C. wrairi; lane 7, C. parvum ferret genotype; lane 8, C. parvum kangaroo genotype; lane 9, C. meleagridis; lane 10, C. parvum mouse genotype; lane 11, Cryptosporidium sp. from a desert monitor; lane 12, C. felis; lane 13, C. parvum dog genotype; lane 14, C. parvum pig genotype. The upper lanes show _Ssp_I digestion products, and the lower lanes show _Vsp_I digestion products. Only partial digestion could be obtained with the kangaroo isolate by _Ssp_I and the C. felis isolate by _Vsp_I.

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