Pathogenicity of Entamoeba dispar under xenic and monoxenic cultivation compared to a virulent E. histolytica

Abstract

SUMMARYTwo xenic isolates and cloned cultures of Entamoeba dispar were submitted to monoxenization using Crithidia fasciculata as the associated organism. Growth in monoxenic cultivation and ability of xenic and monoxenic trophozoites to destroy VERO cells and produce lesions in hamster livers were compared to those of a virulent E. histolytica. Parental and cloned E. dispar under monoxenic cultivation showed a remarkable lower growth than the monoxenic E. histolytica and were avirulent in both in vivo and in vitro tests. When xenically cultured, trophozoites of E. dispar showed a moderate lytic activity against VERO cells (1.5 to 41.8% of destruction) but caused severe hepatic lesions in hamsters as those caused by the virulent E. histolytica (29 to 100% in prevalence and 0.86 to 4.00 in lesion degree). Although E. dispar has not been associated with invasive disease in men, the ability of xenic trophozoites to produce prominent tissue damage in experimental conditions has indicated that some strains have a considerable pathogenic potential when in presence of bacteria.

Human Amebiasis: Breaking the Paradigm?

“…The stool specimen of the patient was cultured in Pavlova’s medium and maintained in a xenic culture containing the patient’s original intestinal flora. This strain was previously characterized as an E. dispar species using PCR [17]. In the next sections some of the phenotypic characteristics of the ICB-ADO strain are described.…”

“…Under this hypothesis, the population densities of both species (in the intestine or the liver) may depend on their particular degree of virulence. In a study conducted by Costa et al [17], it was mention that two isolates of the species E. dispar obtained from Brazilian patients can induce amebic liver abscesses in experimental animals [17,27]. Their results showed that both of the tested isolates (ICB-ADO and MGL) can produce similar cytopathic effects and amebic liver abscesses compared to those produced by a highly virulent E. histolytica EGG strain [17].…”

“…Recent studies have demonstrated that isolates of E. dispar and E. histolytica in xenic or monoxenic culture conditions can increase their virulence, causing larger liver abscesses in laboratory animals in comparison to E. histolytica maintained in axenic culture conditions [17,27]. …”

“…It has been reported that E. dispar may be the causative agent of intestinal symptoms in humans [15–17]. Using an animal model, it has also been demonstrated that this species can cause tissue lesions in the intestine and serious damage to epithelial cells [18–21].…”

“…Furthermore, we report the genotyping of an isolate obtained from a Brazilian patient clinically diagnosed with non-dysenteric amebic colitis, a strain previously characterized as an E. dispar species using PCR [17]. The stool specimen of the patient was cultured in Pavlova’s medium in the presence of the original intestinal flora.…”