DIFFERENTIAL DETECTION OF ENTAMOEBA HISTOLYTICA AND ENTAMOEBA DISPAR USING PCR-BASED ASSAY
Soad Mahmoud, Mona H Elmotayam, Hany A Afify, Magda A Elsettawy, Ghada M Fathy, Fatma A Abdel-Naiem and Mohamed A Fouad*.
Department of Medical Parasitology, Faculty of Medicine, Zagazig University, Egypt.
*Department of Medical Microbiology, Faculty of Medicine, Benha University, Egypt.
Background: E. histolytica is endemic in large parts of the world and is considered responsible for millions of cases of dysentery and liver abscess each year and responsible for up to 100.000 deaths per year. Traditionally, the laboratory detection of E. histolytica in human feces has relied upon the microscopic examination of fresh or fixed stool samples. However, the recent identification of E. dispar as a separate but nonpathogenic species which is morphologically indistinguishable from E. histolytica and does not require treatment has indicated the need of alternative methods for detection which are able to differentiate between the two organisms. So this work aimed to evaluate PCR technique as an effective diagnostic method of E. histolytica and to differentiate it from E. dispar. Also evaluation of PCR technique in comparison with ordinary parasitological examination as a diagnostic method of E. histolytica /E. dispar. Methodology: The present study was carried out on 60 patients aged from 3 years up to 65 years, 50 subjects from outpatient clinics of Zagazig University Hospital, 40 diagnosed microscopically as E. histolytica/dispar infected persons, and 10 cases proved microscopically to be infected with parasitic infections other than E. histolytica E. dispar complex. This group was included in this study to show if any cross reaction would occur with the specific primer of E. histolytica or E. dispar during the performance of PCR technique. Ten clinically and microscopically negative subjects were included as a control negative group. Stool samples were examined for detection of E. histolytica parasite using direct smear, iodine stained smear, formol ether concentration technique and PCR technique. Results: In symptomatic patients, E. histolytica was more prevalent than E. dispar (50% and 35%) respectively. In asymptomatic subjects, E. dispar was more prevalent than E. histolytica. PCR technique showed high sensitivity and specificity (100%) and (95%) respectively in relation to other techniques. Conclusion: PCR technique is a sensitive, reliable method, not time consuming as traditional method. It is used for accurate diagnosis of amoebiasis; it also can discriminate between pathogenic and non-pathogenic amoeba species; however it is expensive and require high technical experience.
December 2011