New cryptosporidium genotypes in HIV-infected persons.

Protozoan apicomplexan parasites from thegenus Cryptosporidium infect a wide variety ofhosts (1). The parasites are transmitted tohumans through contaminated drinking water(2), contact with infected animals, and contactwith infected persons (3). In the immunocompe-tent, cryptosporidiosis manifests itself as self-limited diarrhea, sometimes accompanied bynausea, abdominal cramps, fever, and vomiting.In the immunodeficient, however, cryptosporidiosismay be severe, chronic, and life-threatening (4).Cross-infection experiments, in whichCryptosporidium oocysts were obtained fromanimals of one species and fed to animals ofanother species, have investigated the hostspecificity of this parasite (5). The differencesobserved in the host range of putative C. parvumisolates led to a proposal to establish theCryptosporidium isolate originating from guineapigs, morphologically indistinguishable fromC. parvum, as a new speciesSC. wrairiSsolelyon the basis of experimental infection (6). Thepossibility of many Cryptosporidium speciesfostered the development of techniques suitablefor typing isolates. Commonly used techniquesare isoenzyme analysis (7), Western blotting(8,9), random amplified polymorphic DNAanalysis (10-12), polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP) analysis (13,14), and PCR followed byDNA sequencing (11,15-19).Early studies of the polymorphism of isolatesclassified as C. parvum found significantgeographic variation among isolates (20) in theregion coding for the small subunit ribosomalRNA (SSU-rRNA), commonly used for taxonomicclassification. Recently, it has been shown (21)that one of the sequences used in this analysis(22) was erroneously identified as a C. parvumsequence, while in fact it was C. muris. Morerecent work (e.g., Le Blancq et al. [23] andGenBank entry AF040725) has shown that theSSU-rRNA region of the C. parvum zoonotic(bovine) genotype does not show heterogeneityand is practically identical to the sequencesubmitted to GenBank in 1993 (accessionnumber L16996, [24,25]).Recently, consistent results of typing bovineand human C. parvum isolates led tounequivocal recognition of two genotypes ofC. parvum. These two genotypes were reproduc-ibly differentiated by sequencing the SSU-rRNAcoding region (16), sequencing the Cryptosporidiumthrombospondin-related adhesion protein (TRAP-C2) gene (17), and PCR-RFLP analysis of theCryptosporidium oocyst wall protein (COWP)gene (15). Thus far, the anthroponotic genotype(genotype 1) has been found only in infectedhumans, while the zoonotic genotype (genotype2) has been found both in infected humans and inlivestock, e.g., cows, lambs, goats, and horses.The published partial SSU-rRNA sequence of