ABSTRACT
In this study, 50 stool specimens collected from severe diarrheic patients were examined microscopically for protozoan parasites mainly, Cryptosporidium parvum. Stool examination revealed 22 cases with C. parvum, 8, with E. histolytica, 14 with G. Intestinalis and 6 were parasite-free. The results were compared with the established nested PCR assay to detect DNA directly from stool specimens. After the extraction of DNA from stool, a 402-bp fragment of C. Parvum DNA was amplified with 2 26-mer outer primers. The amplified products, 194-bp DNA fragment, were used for a second run. This study indicated that the used primers are specific for DNA of C. parvum. PCR detected 28 positive cases, 6 of them were negative by AF stool examination, which eventually confirmed to be positive by several successive examinations of the stool and/or duodenal aspiration. Microscopy exhibited 78.5% sensitivity and 100% specificity compared with 100% specificity and sensitivity with PCR. Consequently, it was concluded that PCR is more sensitive and easier to interpret, but required more hands-on time to perform and is more expensive than microscopy. However, PCR batch analysis reduces the cost considerably