Genotypic and phenotypic characterization of Cryptosporidium parvum isolates from people with AIDS

Genotypic analysis of Cryptosporidiun parvum has demonstrated the presence of two subgroups within the species, whereas biochemical and antigenic characterization have shown more heterogeneity. The clinical relevance of these observations is unknown. C. parvum isolates from people with AIDS were studied with respect to parasite genotypes and virulence in cell monolayers and laboratory animals. Ten elf 13 oocyst samples had a characteristic human-associated (H) genotype; 3 had a genotype typic;il of calf-excreted oocysts (C), Virulence in cell culture was mildly or markedly lower in the 5 isolate:; tested (4 H and 1 C) compared with the GCH1 reference isolate, H isolates did not infect newborn ICR mice, whereas 1 of the 2 C isolates tested did. These findings reinforce the concept of C. parvum genetic subgroupings that correlate to some extent with infectivity and suggest that additional heterogeneity is present within the subgroups.