Virulence of nonpathogenic zymodemes of Entamoeba histolytica isolates from asymptomatic subjects in Calcuta, India

ABSTRACT

The zymodene and virulence of 31 Entamoeba histolytica isolates obtained from asymptomatic human subjects in Calcuta, India are described. Virulence was measured by the extent of lesion diameter (mm) induced by each isolated in the liver of golden hamsters and resistance of isolates to non-immmune hamster sera in vitro. Two nonpathogenic zymodemes, III (N=17) and IV (N=14), were detected among 31 isolates by isoenzyme electrophoresis. Most of the zymodeme III isolates were moderately to highly virulent while a quarter of the zymodeme IV were invasive although with low virulence. The virulence of the isolates was found to have a significant positive correlation (r=0.96, P<0.001) with their greater resistance to complement-mediated lysis. The data suggest that the virulence of E. histolytica is probably not related to its zymodeme