[Application of the polymerase chain reaction to the epidemiological study of amoebiasis]

The polymerase chain reaction (PCR) has been used in studying the pathogenicity of Entamoeba histolytica in a rural community in Shandong province. Formalin-fixed stool samples were used for extraction of DNA. The PCR amplifications were performed using two sets of primer that discriminate between pathogenic and nonpathogenic E. histolytica. All of the 32 cases of cyst carrier diagnosed microscopically were identified as positive. Three groups were defined through PCR analysis: 6 cases (18.8%) were positive for pathogenic but negative for nonpathogenic, 25 cases (78.1%) were negative for pathogenic but positive for nonpathogenic, and only one case (3.1%) was positive for both pathogenic and nonpathogenic. The cases found to be pathogenic by PCR were also closely correlated with their clinical manifestations (diarrhea) (OR = 31.5, P < 0.005). All of the control cases showed negative reaction to PCR. PCR has also been used to study the epidemiology of amoebiasis in a small population group with 40 persons in the same province. Both positive rates by PCR on pathogenic and nonpathogenic were 10%. The results showed that this new technique can be applied in the field for the epidemiological studies of pathogenic and nonpathogenic E. histolytica.