Genetic variability of E. histolytica strains based on the polymorphism of the SREHP gene using nested PCR-RFLP in Erbil, North Iraq

Abstract

E. histolytica is an intestinal parasite that causes asymptomatic infection mostly; however, it may also cause amoebic dysentery and liver abscess. Molecular identification is required in epidemiological studies due to the presence of morphologically identical nonpathogenic species. Therefore, this study was conducted to first evaluate the prevalence rate of E. histolytica among symptomatic individuals of Erbil city, and to investigate the genetic diversity of the parasite in a limited geographic area. Accordingly, a total of 2026 samples were examined microscopically, and confirmed by nested PCR for 18s rRNA gene. The results showed that the prevalence rate of E. histolytica was 1.97% (40 samples) among symptomatic patients. The SREHP gene was used as a marker to show the genetic polymorphism of E. histolytica; however, to compare the genetic diversity of symptomatic with asymptomatic isolates, 57 asymptomatic samples were obtained from our previous study. The amplified products of the SREHP gene were digested by AluI endonuclease, and DNA banding patterns were analysed. Results showed 29 different DNA patterns among the 97 symptomatic and asymptomatic samples, 62 of which shared similar DNA patterns. However, 8 different DNA patterns were observed among asymptomatic samples, whereas 15 distinct patterns were observed among symptomatic isolates. In conclusion, this study found that the prevalence rate of E. histolytica was relatively low; relatively high genetic diversity was observed in a restricted endemic area; with higher rates of variability in symptomatic rather than in asymptomatic isolates, indicating a possible correlation between the genotype of E. histolytica and their clinical outcome.

Genetic Variability of Entamoeba histolytica Strains

“…For examples, studying STR regions in tRNA genes of E. histolytica revealed interspecies variation that may related to the clinical outcome of the disease and may provide evidence for the geographic origin of the infection [67]. Moreover, studies documented the presence of high genetic diversity among E. histolytica strains using PCR-RFLP analysis on SREHP gene and addressed the association of the strains with the clinical presentation of the disease [8,44,68]. The investigations based on chitinase gene sequence repeat suggested the existence of strains of E. histolytica that could be non-pathogenic, invasive for the intestinal mucosa or invasive for liver tissue [46,69,70].…”

“…It has been suggested that the presence of these genetic alterations could have either permitted the parasite to more readily evade host immune responses or be related to higher virulence, causing more severe clinical presentations [8].…”

Molecular Characterization of E. Histolytica Strains Based on the Serine Rich Entamoeba Histolytica Protein (Srehp) And Chitinase Genes.

“…Understanding the nature of amoebic virulence is important, several studies have shown that the genetic factors do in uence the virulence of the infection. Among the many loci used to investigate the epidemiology of E. histolytica, Chitinase and SREHP are among the important markers used in molecular epidemiological studies [11].…”

“…Different types of genes associated with the outcome of amebic infection have been detected, Among the many loci used to investigate the outcome of E. histolytica infection, SREHP and chitinase are one of the important markers used in these studies [11]. These proteins have been shown to be potentially useful for determination of intra-species variation among E. histolytica and in investigating the molecular epidemiology of amebiasis.…”