Molecular Diagnosis of Strongyloides stercoralis Infection by PCR Detec¬tion of Specific DNA in Human Stool Samples

Strongyloidiasis is mostly an asymptomatic infection and diagnosis of latent infec­tions is difficult due to limitations of current parasitological and serological methods. This study was conducted to set up a PCR-based method for molecular diagnosis of Strongyloides stercor­alis infection by detection of copro-DNA in stool samples. A total of 782 fresh stool samples were collected and examined by agar plate culture. Among those sixteen stool samples, which confirmed to be infected with S. stercoralis were exam­ined as positive control to set up each single and nested PCR, using two primer sets design­ing to amplify partial ribosomal DNA of S. stercoralis genome. Since, single PCR method yielded higher efficacy in detecting positive samples, in the second step, 30 stool samples, which found negative for S. stercoralis by agar plate culture of single stool sample, were examined by sin­gle PCR. Data analysis was performed using McNemar's χ2 test, with consideration of a P-value of <0.05 as indication of significant difference. In amplification of DNA extracted from stool samples, single PCR detected S. stercor­alis DNA target in all 16 positive samples, while nested PCR amplified DNA in only 75% of sam­ples. In the second step, single PCR amplified S. stercoralis extracted DNA in 5 out of 30 sam­ples which were negative by coproculture. Single PCR method amplifying a short (100bp) target represented more efficacies for detection of S. stercoralis in faecal examination compared to agar plate culture and nested PCR, which amplified longer target.