Only one in ten Entamoeba histolytica infections is invasive but they are responsible for an annual death toll of up to 100,000 people. A key question in amoebiasis is, therefore, what is responsible for the variable outcome of infection. To investigate whether it is linked to the genotype of the infecting strain, we developed 6 pairs of species-specific primers for genotyping after investigating 46 potentially polymorphic short tandem repeat loci adjacent to tRNA genes that were identified during the E. histolytica genome project. We tested the primers using E. histolytica samples from Bangladesh and 11 other countries. Results revealed that the genotypes present in 3 different clinical populations - asymptomatic, diarrhoeal/dysenteric and liver abscess - were different from each other. A few individual genotypes also showed links to the outcome of infection although their sample coverage was low and therefore they had little predictive value. Although the loci used as polymorphic markers are unlikely to be directly responsible for the outcome of infection, the results do suggest that parasite genetic factors are at least partly responsible. Our multilocus genotyping method is simple and reliable as it amplifies DNA extracted from axenic or xenic culture, stool samples, and liver abscess pus samples. We believe that these markers will help in studying the patterns of transmission of this important disease and the epidemiological links between individual infections
