The use of the antifungal agent miconazole as an inhibitor of Blastocystis hominis growth in Entamoeba histolytica/E. dispar cultures

Abstract

SUMMARYIn regions with high prevalence, Blastocystis hominis is frequently found in association with Entamoeba histolytica/E. dispar in xenic cultures. Its exacerbated growth is often superimposed on the growth of amebas, thus impeding the continuation of the amebas in the culture, within a few generations. The present study reports on the excellent efficacy (100%) of the antifungal agent miconazole in eliminating B. hominis from cultures of E. histolytica/E. dispar, thereby maintaining the integrity of the trophozoites of the amebas. Nystatin presented low efficacy (33.3%). KEYWORDS: Blastocystis hominis;Miconazole; Entamoeba histolytica; Entamoeba dispar; Culture.The human intestinal protozoan Blastocystis hominis causes infection that is often asymptomatic, and is found at higher prevalence in developing countries 1 . Although it is one of the most common parasites encountered in stool samples, its pathogenicity is still controversial 4 . In regions of high endemicity, B. hominis is frequently found in xenic cultures of Entamoeba histolytica/E. dispar. In cultures it tends to grow vigorously and, unless it is eradicated completely at an early stage, it eventually overgrows and kills all amebas, usually within a few generations 3,7 .There are some methods for eliminating B. hominis from ameba cultures. DOBELL & LAIDLAW 3 described ameba cyst treatment with a 0.2% solution of hydrochloric acid, at room temperature, for two hours (or with 0.1 N HCl for 10 minutes, according to CLARK & DIAMOND 2 ), followed by washing with distilled water and reinoculation into a culture medium to which a suitable bacterial flora has been added. The acid kills B. hominis, fungi and bacteria, while leaving the cysts intact. In the method described by SMEDLEY 7 , ameba cultures are pelleted, resuspended in distilled water at room temperature for 20 minutes, repelleted, and then this material is inoculated into fresh culture medium. This last procedure is simple, and it is not necessary to use separate bacterial flora. However, it needs to be repeated a couple of times before the B. hominis is completely eliminated 2 . The use of acriflavin (with or without subsequent passage through a medium containing lactic acid) for decontaminating the cultures is generally unsatisfactory, presenting adverse effects on the bacterial flora and, directly or indirectly, on the amebas 2,3,7,8 . According to SILVA 6 , culture treatment with nystatin at 25-50 UI/mL concentrations does not present high efficacy in decontamination, and B. hominis resistance to nystatin occurs in some cases.This study reports on the excellent inhibitory action of the antifungal agent miconazole on B. hominis found in cultures of amebas, thereby keeping the amebas alive. It was approved by protocol number 217/ 03, from the ethical committee of Oswaldo Cruz Foundation.Twenty fresh stool samples (from people living in the municipality of Barcelos, Amazonas State, Brazil) containing cysts of E. histolytica/ E. dispar were inoculated into tubes containing 10 mL of modified Pa...

Histopathological and immunohistochemical study of the hepatic lesions experimentally induced by Entamoeba dispar

“…Miconalzole was used to eliminate Blastocystis and yeast, which could affect the amoeba's growth in the culture. 13 …”