Genotyping of E. histolytica strains detected in Parma (Italy): preliminary results.

objectives and methods Current understanding of the epidemiology of amoebiasis still lacks the knowledge of what determines the outcome of E. histolytica (Eh) infections. It is possible that one of the determining factors resides in the genotype of the parasite. In this study we used a recently described PCR assay based on short tandem repeat (STR)-containing loci linked to tRNA genes (Ali et al., 2005) to investigate the extent of genetic diversity among Eh strains from clinical samples of patients with amoebic colitis or liver abscess. Nineteen samples (faeces, liver abscess and intestinal biopsy samples) belonging to 8 patients with amoebiasis (5 intestinal, 3 extraintestinal) were analysed. results and conclusion On the basis of the variability of the number of STRs at the six loci, all strains had unique genetic fingerprints (except for 2 strains from the faeces of 2 patients belonging to the same family), reflecting a high degree of polymorphism in the population studied. Interestingly, in a patient for whom sample from both faeces and liver abscess was available, the strains from the two types of samples had different genotypes. This suggests a possible role of the genotype in determining tissue tropism, a hypothesis that certainly needs to be confirmed on a significant number of strains from faeces and abscesses of individuals with extraintestinal disease. Sequencing of the amplification products at all 6 loci for all the strains analysed is in progress in order to confirm genotype assignment which was done primarily on the basis of the estimated PCR product sizes in agarose gel. A genotyping study in Bangladesh (Ali et al., 2007) has suggested that the parasite genome plays a role in determining the outcome of infection with Eh. It is important to know whether this observation can be replicated in other parts of the world. To investigate this, extensive sample collections from additional geographical areas are needed. Therefore, though not inferred from a large population of Eh strains, we are confident that the results of the present study, when taken together with genotyping data produced on an increasing number of strains isolated from asymptomatic and symptomatic patients in different geographical areas, could contribute to a deeper understanding of the link between Eh genotype and the outcome of infection.