Extensive polymorphism in Cryptosporidium parvum identified by multilocus microsatellite analysis

Restriction fragment length polymorphism and DNA sequence analysis discern two main types of Cryptosporidium parvum. We present a survey of length pol ymorphism at several microsatellite loci for type I and type 2 isolates. A total of 14 microsatellite loci were identified from C. parvum DNA sequence s deposited in public databases, All repeats were mono-, di-, and trinucleo tide repeats of ii AT, and AAT, reflecting the high AT content of the C, pa rvum genome. Several of these loci showed significant length polymorphism, with as many as seven alleles identified for a single locus. Differences be tween alleles ranged from 1 to 27 bp, Karyotype analysis using probes flank ing three microsatellites localized each marker to an individual chromosoma l band, suggesting that these markers are single copy, Po a sample of 19 is olates for which at feast three microsatellites were typed, a majority of i solates displayed a unique multilocus fingerprint. Microsatellite analysis of isolates passaged between different host species identified genotypic ch anges consistent with changes in parasite populations.