Congo red effect on cyst viability and cell wall structure of encysting entamoeba invadens

Background. The cell wall of Entamoeba invadens cysts is composed of chitin microfibrils as the main structural component. It has been demonstrated in yeast that the chitin cell wall assembly is altered by dyes such as Congo red (CR) and Calcofluor. Methods. The purpose of this work was to study the cell wall assambly under the effect of CR dye on encysting E. invadens by means of light and electron microscopy, after the ammebas were subjected to the effect of 100-2,000 µg CR/mL. Experiments were performed either in BI-S-33 or in mLG media. Results. Trophozoit growth was not inhibited by 100-1,000 µg/mL CR after 8 days of incubation in BI-S-33 medium. However, low levels of growth were observed with 2,000 µg/mL of dye. No significant differences in morphologically viable (hyaline) cyst production occurred after 24-48 hm when 100 µg CR/mL was used, while the highest concentration of CR (2,000 µg/mL) resulted in a significant decrease of hyaline cyst yield; dead cysts prevailed in cultures, particularly at 72 h of CR treatment. Differentiation of amebas incubated in the presence of 500-2,000 µg/mL CR produced abnormal chitin deposits, rendering irregulary thick or double cell walls, as shown by transmission and scanning electron microscopy. Cyst cultures obtained under 100 µg/mL CR produced as many trophozoites as did the control when they were incubated in BI-S-33, but only low numbers of trophozoites were found in culture cysts obtained under higher CR doses. Conclusion. Our results suggest that CR affects E. invadens encystment, alters the cell wall formation, and also affects the cyst viability

Ultraestructura de quistes de Entamoeba invadens obtenidos bajo el efecto de emetina, tinidazol y rifampicina / Ultraestructure of entamoeba invadens cysts obtained under the effect of emetine, tinidazole and rifampin

Se determinaron las concentraciones inhibitorias mínimas (CIM) de emetina, tinidazol y rifampicina para trofozoítos de E. invadens, así como la ultraestructura de quistes obtenidos después de 22 y 45 horas, en presencia de la CIM de los fármacos. Bajo el efecto de tinidazol o de rifampicina los quistes obtenidos mostraron numerosas vacuolas que contenían elementos membranosos y vesículas llenas de material amorfo electrodenso; algunas de éstas se observaron en las proximidades de la membrana plasmática. En los quistes obtenidos en presencia de emetina, el citoplasma presentó numerosas vesículas y cisternas aplanadas particularmente después de 22 horas de incubación en médio de enquistamiento, las que disminuyeron después de 45 horas de diferenciación; se observaron además vasículas con material electrodenso próximas a la membrana plasmática. Las paredes celulares de los quistes obtenido bajo el efecto de los fármacos mencionados fueron irregulares tanto en el arreglo fibrilar como en el espesor; adicionalmente, bajo los efectos de tinidazol y emetina las paredes de los quistes se perdieron parcial o totalmente, observándose acúmlos de éstas entre los quistes. Los resultados sugieren que la CIM de los fármacos empleados provocaron un retardo en el proceso de difereciación de E. invadens y, posiblemente, interfieran con el ensamble de la pared celular y con la adherencia de ésta a la membrana plasmática durante el enquistamiento