Evaluation of Giardia duodenalis viability after metronidazole treatment by flow cytometry

Giardia duodenalis (syn. lamblia; syn. intestinalis) susceptibility testing is not routinely performed because the classical culture methods are very time-consuming and laborious. We developed a novel flow cytometry (FC) assay to evaluate the susceptibility of G. duodenalis trophozoites to metronidazole (MTZ). Different concentrations of MTZ were added to cultures of trophozoites (10 5 /mL) and the cultures were incubated for different periods. The 50% inhibitory concentration was calculated and propidium iodide (PI) was used to quantify the number of dead cells. After treatment, PI-positive trophozoites increased with increasing drug concentration and exposure time. An excellent correlation was found between FC and the classical method. A novel, accurate and reliable method is now available to evaluate G. duodenalis viability. .

Giardia y giardiasis / Giardia and giardiasis

Giardia lamblia es un protozoario parásito que habita el intestino delgado de los seres humanos y de muchos otros vertebrados y es una de las más comunes causas de diarrea en todo el mundo. Durante su ciclo de vida Giardia sufre significativos cambios bioquímicos y morfológicos que le permiten sobrevivir en ambientes y condiciones que de otro modo lo destruirían. Para sobrevivir fuera del intestino del hospedador, los trofozoítos de Giardia se diferencian a quistes, los que se caracterizan por poseer una rígida pared glicoproteica externa que les permiten sobrevivir inclusive frente a la acción de los desinfectantes más comunes. Otro de los mecanismos de adaptación de este parásito es la variación de los antígenos de superficie que le permite a los trofozoítos evadir la respuesta inmune del huésped y generar infecciones tanto agudas como crónicas o recurrentes en individuos infectados. Durante los últimos años se han producido importantes avances en el conocimiento de las bases moleculares de los procesos de enquistamiento y variación antigénica en Giardia que pronostican el pronto hallazgo de nuevos agentes quimioterapéuticos y/o inmunoprofilácticos contra este importante parásito intestinal.

A unique mechanism of nuclear division in Giardia lamblia involves components of the ventral disk and the nuclear envelope

The fine structure of the binucleate, parasitic protist Giardia lamblia during interphase and divisional stages was studied by serial thin sectioning and three-dimensional reconstructions. The earlier sign of nuclear division is the development of a few peripheral areas of densely packed chromatin directly attached to the inner nuclear envelope. An intracytoplasmic sheet of ventral disk components grows from the cell periphery towards one of the nuclei, apparently constricting this nucleus, which becomes located at a ventral bulge. After the basal bodies become duplicated, a full nuclear division occurs in trophozoites, giving two pairs of parent-daughter nuclei. This full division occurs in a dorsal-ventral direction, with the resulting nuclear pairs located at the sides of the two sets of basal bodies. A new ventral disk is formed from the disk-derived sheets in the cell harboring the four nuclei. Cytokinesis is polymorphic, but at early stages is dorsal-to-dorsal. Encysting trophozoites show the development of Golgi cisternae stacks and dense, specific secretory granules. 3-D reconstructions show that cysts contain a single pair of incompletely strangled nuclei. The dividing Giardia lacks a typical, microtubular spindle either inside or outside the nuclei. The nuclear envelope seems to be the only structure involved in the final division of the parent-daughter nuclei.

Giardia duodenalis: Analysis of humoral immune response in experimentally infected gerbils (Meriones unguiculatus)

In this work, we have analyzed the humoral immune response in Mongolian gergils infected with Giardia duodenalis trophozoites of strains P-1 ad WB. The course of infection in the animals was assessed by monitoring cyst shedding in feces, and serum samples were collected at weekly intervals to measure antibody levels by ELISA. Parallel studies were carried out to determine the patterns of total and surface antigens of the parasite recognized by antibodies using Western blot and radioimmunoprecipitation (RIP) assays with the use of homospecific enzyme conjugates. Typical patterns of cyst shedding were observed in the infected animals and cyst numbers per grams of feces were consistently higher in gerbils infected with WB strain. Antibody levels to G. duodenalis antigens were observed by week 2 post-infection and were still detectable 4 months after infection. G. duodenalis antigen showed a complex but quantitatively and qualitatively different recongnition pattern by infection-induced antibodies in Western blot assays which related to infecting strain. However, RIP assays showed a more restricted and common pattern of recognition of surface antigens from either strain. Taken together, the data obtained in this study provides further information regardin direct comparisons among infecting strain, pattern of infectivity, and host immune response toward G duodenalis antigens in the gerbil model