Role of DNA probes in characterization of pathogenic and non-pathogenic E. histolytica.

Various tests have been described to differentiate the pathogenic and non-pathogenic types of E. histolytica. Recently DNA hybridization has been described to differentiate between the two subtypes. Using common HMC probe the presence of E. histolytica in stool was confirmed. Then on the basis of hybridization with DNA probe P 145 (pathogenic) and B 133 (non-pathogenic) E. histolytica was characterized as being pathogenic and non pathogenic respectively. Out of 137 patients studied 88 were symptomatic and 49 asymtomatic. 65 patients harboured E. histolytica as proved by microscopic examination of stool. Sixty-eight stool samples tested positive for DNA hybridization with common HMC probe, this included 65 microscopy positive samples and 3 microscopy negative samples. This gives a sensitivity of 100% and 96% specificity. All the 68 samples were then subjected to hybridization with P 145 and B 133 DNA probes. Out of 88 symptomatic patients stool samples of 57 patients were microscopy positive, however 58 were positive by common HMC probe and all of these were P 145 (pathogenic) positive and B 133 (non-pathogenic) negative. Of the 49 asymptomatic cases 8 were E. histolytica positive on microscopy and 10 positive on hybridization with common HMC probe and all 10 were P 145 negative and B 133 positive. It can be thus concluded that DNA hybridization is a reliable way to differentiate between pathogenic and nonpathogenic E. histolytica.