Molecular characterization of Cryptosporidium isolates from humans and other animals using random amplified polymorphic DNA analysis.

Genetic variation in 25 Cryptosporidium isolates was analyzed using the random amplified polymorphic DNA (RAPD) technique. Simple reproducible polymorphisms were generated (using five primers) from Cryptosporidium DNA that was free of contaminating bacterial DNA. The results generated by four of the five primers were statistically correlated (P < 0.001). The combined data from three primers were used to construct a phenogram using Jaccard's distance. Four groupings could be distinguished. Two C. serpentis isolates from snakes formed a distinct group of their own, whereas C. parvum isolates were divided into two main groups: one containing most human isolates and the other containing mostly domestic animals plus two remaining human isolates. Due to the sensitivity of the RAPD technique, isolates can now be analyzed genetically, directly from fecal samples without further biological amplification. This represents a significant advance on current techniques.