The tRNA Gene-Linked STRs and Other Genetic Typing Methods

Abstract

Only one in ten Entamoeba histolytica infections is invasive but the bacterium is responsible for an annual death toll of up to 100,000 people. A key question in amebiasis is, therefore, what is responsible for the variable outcome of infection. To address whether it is linked to the genotype of the infecting strain, several protein-coding and noncoding genes have been investigated. However, with the use of only tRNA gene-linked short tandem repeat (STR) loci, a signifi cant difference among the genotypes of three different clinical populations-asymptomatic, diarrheal/dysenteric, and liver abscess-was detected. This multilocus genotyping method is simple and reliable as it amplifi es DNA extracted from culture, stool samples, and liver abscess pus samples. As a result, these markers are useful in studying the patterns of transmission of this important disease and the epidemiological links between individual infections. Because tRNA-linked STRs are noncoding DNAs, one caveat of this system is that they may not be directly linked to parasite virulence and may work only as surrogate markers to predict infection outcomes. A novel genotyping method to identify nonsynonymous SNPs that may directly correlate with the parasite virulence is currently underway.