Identification of Blastocystis ST1 in oysters (Crassostrea virginica) collected in self-service markets in Mexico City

Resumen

Blastocystis sp. es un huésped intestinal del tracto digestivo de una gran variedad de organismos vertebrados e invertebrados. El objetivo de este estudio fue determinar la presencia de Blastocystis sp. en ostras americanas (Crassostrea virginica) e identificar su subtipo. Se ana­lizaron las heces de 550 ostras obtenidas de tiendas de autoservicio en la Ciudad de México, con microscopía de fotones mediante un examen directo de heces frescas coloreadas con solución de Lugol. Se aisló el DNA del contenido intestinal de un grupo de ostras para detectar la presencia de Blastocystis sp. y determinar el subtipo al que pertenece, mediante la amplificación por PCR de la región ITS1-5.8S-ITS2. Los amplicones se secuenciaron y luego se tipificaron mediante análisis bioinformático. Se observaron quistes o formas vacuolares de Blastocystis sp. en el 71.3% de las ostras por microscopía óptica. El subtipo (ST) de Blastocystis identificado por PCR en C. Virginica corresponde al ST1 subgrupo A. Concluimos que comer ostras crudas es una posible fuente de infección de Blastocystis sp. para los humanos.

Blastocystis sp. is an intestinal host of the digestive tract of a great variety of vertebrate and invertebrate organisms. The objective of this study was to determine the presence of Blasto­cystis sp. in American oysters (Crassostrea virginica) and to identify its subtype. Stools of 550 oysters obtained from self-services markets in Mexico City were analyzed with photon microscopy by means of direct examination in fresh feces colored with Lugol solution. DNA from the intestinal content of a group of oysters was isolated to detect the presence of Blastocystis sp. and to determine its subtype, by means of PCR amplification of the ITS1-5.8S-ITS2 region. The amplicons were sequenced and later typed by bioinformatic analysis. Cysts or vacuolar forms of Blastocystis sp. in 71.3% of the oysters were observed by light microscopy. The Blastocystis subtype (ST) identified by PCR in C. virginica corresponds to the ST1 subgroup A. We conclude that consumption of these raw oysters is a possible source of infection of Blastocystis sp. for humans.