PATHOGENICITY OF Blastocystis sp. TO THE GASTROINTESTINAL TRACT OF MICE: RELATIONSHIP BETWEEN INOCULUM SIZE AND PERIOD OF INFECTION / Histopatogenicidade de Blastocystis sp. para o trato gastrointestinal de camundongos: relação com inóculo e tempo de infecção

The pathogenic potential of Blastocystis sp. in experimental models requires further investigation. In this work, the pathogenicity of this parasite in the gastrointestinal tract of male Swiss mice was evaluated according to the inoculum size and period of infection. Animals were infected intragastrically, with 100, 500, 1,000, 5,000 and 10,000 Blastocystis sp. vacuolar forms obtained from a mixture of eight human isolates cultured axenically in Jones' medium. After seven, 14, 21, 28 and 60 days of infection, the animals were sacrificed and fragments of the small intestine (duodenum), large intestine, and cecum were subjected to histopathological analysis. Blastocystis sp. triggered an inflammatory response in the different tissues analyzed, with a predominance of mononuclear cells. The parasite was found in the muscular layer of the cecum, showing its invasive character. Larger inocula triggered inflammatory processes earlier (seven days) than smaller ones (from 21 days). We conclude that, in the proposed model, the pathogenicity of Blastocystis sp. isolates that were studied is related to inoculum size and period of infection.

Pouco é sabido sobre o potencial patogênico de Blastocystis sp. em modelos experimentais. Neste trabalho a patogenicidade desse parasito para o trato gastrointestinal de camundongos Swiss machos foi avaliada de acordo com o inóculo e tempo de infecção. Os animais foram infectados, via intragástrica, com 100, 500, 1.000, 5.000 e 10.000 formas vacuolares de Blastocystis sp. obtidos a partir de uma mistura de oito isolados humanos cultivados axenicamente em meio Jones. Após 7, 14, 21, 28 e 60 dias de infecção os animais foram sacrificados e fragmentos do intestino delgado (duodeno), grosso e ceco foram retirados para análise histopatológica. Blastocystis sp. desencadeou resposta inflamatória nos diferentes tecidos analisados, com predominância de infiltrado mononuclear. No ceco o parasito foi encontrado na túnica muscular mostrando seu caráter invasivo. Inóculos maiores desencadearam processos inflamatórios mais precocemente (7 dias) e inóculos menores mais tardiamente (a partir de 21 dias). Conclui-se que no modelo proposto a patogenicidade dos isolados de Blastocystis sp. estudados tem relação com o inóculo e tempo de infecção.

Evidencias y mecanismos de patogenicidad de Blastocystis sp / Evidence and pathogenicity mechanisms of Blastocystis sp

INTRODUCCIÓN: durante las últimas dos décadas se acumularon evidencias que favorecen la aceptación del carácter patógeno de Blastocystis sp. Sin embargo, esos argumentos no son aún del conocimiento de la inmensa mayoría de los profesionales relacionados con el diagnóstico, tratamiento y control de las parasitosis intestinales, en general, y de la blastocistosis, en particular. OBJETIVOS: revisar lo publicado sobre las evidencias en favor de la patogenicidad de Blastocystis sp. y hasta dónde la información acumulada permite exponer los mecanismos por los cuales este parásito puede causar daños en el hospedero humano. MÉTODOS: con el auxilio de diferentes buscadores electrónicos, se realiza una revisión de los artículos sobre patogenicidad de Blastocystis sp. publicados durante el período 1994-2014. Puntualmente, algunas monografías y artículos originales fechados con anterioridad al intervalo mencionado también fueron consultados. CONCLUSIONES: evidencias clínicas, fenotípicas y genotípicas acumuladas durante los últimos tres lustros favorecen la aceptación del carácter patógeno de Blastocystis sp. y estas, una vez difundidas ente los profesionales correspondientes, deberán ser tenidas en cuenta para la realización de un mejor diagnóstico, tratamiento y control de esta parasitosis.

INTRODUCTION: Evidence has been gathered in the past two decades which leads to recognizing the pathogenic nature of Blastocystis sp. However, these arguments are still not known to the vast majority of professionals engaged in the diagnosis, treatment and control of intestinal parasitosis in general and blastocystosis in particular. OBJECTIVES: Review publications containing evidence of the pathogenicity of Blastocystis sp. and determine whether the information accumulated allows description of the mechanisms by which this parasite may cause damage to human hosts. METHODS: Various search engines were used to find and review papers published in the period 1994-2014 dealing with the pathogenicity of Blastocystis sp. Several monographs and original papers dated before the above mentioned period were also consulted. CONCLUSIONS: Clinical, phenotypic and genotypic evidence accumulated in the last fifteen years lead to recognizing the pathogenic nature of Blastocystis sp. Once made known to the corresponding professionals, such evidence should be borne in mind to improve the quality of the diagnosis, treatment and control of this parasitosis.

Patogenicidad de Blastocystis sp. Evidencias y mecanismos / Pathogenicity of Blastocystis sp. Evidence and mechanisms

Introducción: durante las últimas dos décadas se acumularon evidencias que favorecen la aceptación del carácter patógeno de Blastocystis sp. Sin embargo, esos argumentos no son aún del conocimiento de la inmensa mayoría de los profesionales relacionados con el diagnóstico, tratamiento y control de las parasitosis intestinales, en general, y de la blastocistosis, en particular. Objetivos: revisar lo publicado sobre las evidencias en favor de la patogenicidad de Blastocystis sp. y, hasta dónde la información acumulada permite, exponer los mecanismos por los cuales este parásito puede causar daños en el hospedero humano. Métodos: con el auxilio de diferentes buscadores electrónicos, se realiza una revisión de los artículos sobre patogenicidad de Blastocystis sp. publicados durante el período 1994-2014. Puntualmente, también fueron consultados, algunas monografías y artículos originales fechados con anterioridad al intervalo mencionado. Resultados: se expone y analiza, con un enfoque académico y asistencial, la información actualizada sobre los temas seleccionados. Conclusiones: evidencias clínicas, fenotípicas y genotípicas acumuladas durante los últimos tres lustros favorecen la aceptación del carácter patógeno de Blastocystis sp. y éstas, una vez difundidas ente los profesionales correspondientes, deberán ser tenidas en cuenta para la realización de un mejor diagnóstico, tratamiento y control de esta parasitosis(AU)

Introduction: during the last two decades, evidence supporting the pathogenic character of Blastocystis sp. accumulated. Nevertheless, those arguments are still unknown by the great majority of professionals related with diagnosis, treatment and control of the intestinal infectious in general, and of the blastocystosis in particular. Objectives: to review published materials about pieces of evidence that support the acceptance of the pathogenicity of Blastocystis sp., and to what extent the information accumulated allows revealing the mechanisms by which this parasite causes damage to the human host. Methods: through different search engines, papers about pathogenicity of Blastocystis sp. published during 1994-2014 period were reviewed. Additionally, some monograph and papers dated previously to the mentioned interval were also consulted. Results: updated information about the selected topics, with academic and practical approach, were presented and analyzed. Conclusions: clinical, phenotypic and genetic pieces of evidence accumulated during the last fifteen years support the pathogenic character of Blastocystis sp. Once they are adequately integrated into the practice of the corresponding professionals the diagnosis, treatment and control of blastocystosis could be improved(AU)

Algunas consideraciones acerca de Blastocystissp, un parásito controversial / Some considerations about Blastocystis sp, a controversial parasite / Algumas considerações sobre Blastocystis sp, Um parasita controverso

Blastocystis es un organismo unicelular, anaerobio y uno de los parásitos intestinales de mayor prevalencia a nivel mundial. Durante mucho tiempo su ubicación taxonómica fue difícil de definir. Actualmente es considerado el único parásito humano del Reino Chromista. Se le reconocen numerosas formas evolutivas (vacuolares, granulares, ameboidales, avacuolares, multivacuolares y quísticas) que conforman un ciclo vital aún en estudio. Los quistes son las formas de resistencia y transmisión. Se lo considera un parásito zoonótico con 9 subtipos que pueden tener diferentes especificidades entre hospedadores humanos y animales. Su carácter patógeno ha sido motivo también de controversia dado que puede presentar infecciones asintomáticas o sintomáticas con manifestaciones digestivas, y dérmicas, entre otras. El diagnóstico de laboratorio puede ser microscópico o mediante cultivos, serología y técnicas moleculares.

Blastocystis is an anaerobic, unicellular organism and it is one of the most prevalent among intestinal parasites. It has a worldwide distribution. Nowadays, it is considered the only human parasite that belongs to the kingdom Chromista. Many morphological forms of the parasite are known: vacuolar, granular, amoeboid, avacuolar, multivacuolar and cyst. Its life cycle is not completely understood. Cysts are the forms of resistance and transmission. It is considered a zoonotic parasite with 9 subtypes, with different specificities for human and animal hosts. Its pathogenesis is controversial because it can cause asymptomatic and symptomatic infections, with gastrointestinal and cutaneous manifestations. Laboratory diagnosis may be performed by microscopic, cultural, serological and molecular techniques.