A amebíase mantém sua importância epidemiológica em países subdesenvolvidos onde sua prevalência a converteu na parasitose de maior morbidade e mortalidade após malaria e esquistosomose. Em regra, tanto o diagnóstico clínico como os levantamentos epidemiológicos assentam na identificação microscópica de cistos e/ou trofozoítos em extractos fecais. Este procedimento requer pessoal muito bem treinado, é laborioso, e frequentemente fornece resultados contraditórios. Para obviar estas dificuldades, no presente trabalho montamos uma técnica de diagnóstico imunoenzimático baseado na captura de um antígeno de 96 kDa presente nas fezes de indivíduos infectados pela E. hystolytica (COPROELISA-Eh). Triplicatas de 117 amostras fecais processadas pelo método de concentração do formol-éter foram definidas como positivas ou negativas por três microscopistas especialistas em amebíase. Outra alíquota foi submetida ao teste de captura de antígeno por um anticorpo monoclonal contra um antígeno de 96 kDa específico de membranas de cepas patogênicas de E. histolytica. Consideramos como positivos aqueles resultados em que densidades óticas estavam acima do valor dos controles negativos mais 2 desvios padrões. COPROELISA-Eh mostrou 94.4% de sensibilidade, 98.3% de especificidade, 96.2% de valor preditivo positivo e 97.6% de valor preditivo negativo para a deteção de E. hystolytica nas fezes. Em conclusão, o método COPROELISA-Eh é mais sensível e específico do que o exame microscópico dos extratos fecais, não requer pessoal especializado na identificação morfológica das amebas, e permite o processamento de um grande número de amostras simultâneamente.

Amebiasis continues to be of epidemiological importance in underdeveloped countries. Clinical diagnosis and epidemiological setting in a region are based on the fecal microscopic identification of cysts or trophozoites. This procedure requires well trained personnel, is laborious, of low sensitivity and frequently yields false-positives results. The present study was designed to develop an immuno-enzymatic fecal 96 kDa antigen capture test (COPROELISA-Eh) more sensitive and specific than microscopic diagnosis of amebiasis. Triplicates of 177 stool samples processed by the formol-ether concentration method, were defined as positive or negative by three experienced microscopic observers. Another aliquot was submitted to the antigen capture test by a monoclonal antibody against a specific membrane antigen of pathogenic strains of Entamoeba histolytica. Optical densities were interpreted as positive when they exceeded the mean value of negative samples plus two standard deviations. COPROELISA-Eh showed a 94.4% sensitivity, 98.3% specificity, 96.2% positive predictive value and 97.6% negative predictive value for the detection of E. histolytica in feces. COPROELISA-Eh is more sensitive and specific than microscopic examination, does not require specially trained personnel and allows the simultaneous processing of a large number of samples.

Atualmente, tem se discutido muito a dualidade da Entamoeba histolytica. Na tentativa de contribuir no esclarecimento desta questão, investigamos a possibilidade de conversão de amebas avirulentas em virulentas, como também a possibilidade de aumento de virulência de cepas virulentas seguido da associação com bactérias. Para tal utilizamos 5 cepas de E. histolytica, 2 avirulentas e 3 virulentas. As amebas foram associadas com as bactérias Escherichia coli 055 e 0115, demonstradas previamente como hábeis para modificar o comportamento patogênico da E. histolytica. As modificações na virulência das amebas foram avaliadas através do efeito citopático sobre células de mamífero em cultivo e eritrofagocitose. A virulência das cepas patogênicas foi significantemente aumentada depois da associação com bactérias em oposto ao observado para as cepas não patogênicas, as quais não foram influenciadas pela associação com bactérias.

At this moment, the duality of species suggested for E. histolytica is being considered for discussion. In order to contribute to settling this question, we investigated the possibility of conversion of avirulent ameba to virulent ones, as well as, the possibility of increasing virulence of virulent strains, by means of association with bacteria. Five strains of E. histolytica were employed, two of them regarded as avirulent and three virulent ones. Amebas were associated with the bacteria Escherichia coli 055 and 0115, previously demonstrated as capable to modify the pathogenic behavior of E. histolytica. Changes in virulence of amebas were assessed by cytopathic effect upon cultured mammal cells and erythrophagocytosis. The virulence of pathogenic strains was significantly increased after bacteria association in opposition to what was observed for nonpathogenic ones, which were not influenced by bacteria association.

Three clones isolated from the Y strain of Trypanosoma cruzi - YP1, YP2 and YP3 - were adapted to in vitro cultivation in VERO cells. The recovery of the parasites from the Y strain and clone YP3 was similar after 24 hr of contact with cells (3.2% and 2.7%, respectively) and much lower than the recovery of clones YP1 and YP2 (56.7% and 60.0% of inoculum, respectively). After five days incubation, the ratio Trypomastigotes/Amastigotes released into the supernatants was about 90/10 for clone YP1, YP3 and Y strain, and 50/50 for clone YP2. After nine days, the ratio was 62/38 for clone YP1, 97/3 for clone YP3, 81/19 for Y strain and 50/50 for clone YP2. The susceptibility of tissue culture derived trypomastigotes (TCT) to lysis in the presence of chronic chagasic human sera and human complement was assessed using Complement Mediated Lysis reaction (CML). Trypomastigotes from clone YP2 were consistently less susceptible to CML (% lysis less than 20), than parasites from the other clones and Y strain. Parasites of clone YP3 had susceptibility to CML comparable to that of the Y strain (about 70%), while TCT of clone YP1 had intermediary susceptibility (40%).