Genetic polymorphism at the beta-tubulin locus among human and animal isolates of Cryptosporidium parvum

Sequence analysis of a fragment of the beta-tubulin gene was performed on 1 3 isolates of the parasite Cryptosporidium parvum, eight from humans and fi ve from animals. A total of 12 synonymous substitutions and a deletion of t wo bases within the intron sequence were found. This genetic variation defi ned two alleles at the beta-tubulin locus, which can be identified by a sim ple polymerase chain reaction-restriction fragment length polymorphism assa y. A total of 20 isolates were also tested using four available molecular m arkers. These analyses showed congruently that the C. parvum isolates segre gate into two groups, one found exclusively in humans and the other found i n both humans and animals. Since no recombinant genotypes were observed, th e results are consistent with the hypothesis of a substantially clonal repr oduction in this parasite. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.