SIMILARITIES AND DIFFERENCES BETWEEN DNA OF CRYPTOSPORIDIUM-PARVUM AND C-WRAIRI DETECTED BY THE POLYMERASE CHAIN-REACTION

The objective of this study was to determine if primers. probes, and pHC1, a plasmid containing a 2.3 kilobase insert of genomic DNA from Cryptosporidium parvum, would be useful for the detection of Cryptosporidium wrairi DNA using the polymerase chain reaction. C. wrairi DNA was prepared from oocysts recovered from guinea pigs and C. parvum DNA was prepared from the Iowa strain of C. parvum. Two 26-(bp) primers were used to amplify a 452-base pair bp target sequence within the cloned DNA. Similarly-sized PCR products were obtained with the pHC1 plasmid DNA, C. parvum DNA. and C. wrairi DNA. However, a 20-base pair probe did not detect C. wrairi DNA. Sequencing of C. wrairi DNA homologous with the 45-bp segment of C. parvum DNA showed 18 bp changes including bp changes in the segment homologous with the probe. A new probe based on homologous sequences was useful for detection of both species of cryptosporidia. The sequences of the homologous 452-bp segment from the Iowa strain of C. parvum and that segment of C. parvum DNA from the pHC1 plasmid were very similar. Nine base pairs identical in the homologous bp segment of the Iowa strain of C. parvum, C. wrairi and the pHC1 plasmid differed from those previously reported. Previously reported primers and a newly designed probe proved to be useful for detecting C. wrairi DNA.