ABSTRACT Blastocystis sp. is a common intestinal microorganism. The α-L-fucosidase (ALFuc) is an enzyme long associated with the colonization of the gut microbiota. However, this enzyme has not been experimentally identified in Blastocystis cultures. The objective of the present study was to identify ALFuc in supernatants of axenic cultures of Blastocystis subtype (ST)1 ATCC-50177 and ATCC-50610 and to compare predicted ALFuc proteins of alfuc genes in sequenced STs1–3 isolates in human Blastocystis carriers. Excretion/secretion (Es/p) and cell lysate proteins were obtained by processing Blastocystis ATCC cultures and submitting them to SDS–PAGE and immunoblotting. In addition, 18 fecal samples from symptomatic Blastocystis human carriers were analyzed by sequencing of amplification products for subtyping. A complete identification of the alfuc gene and phylogenetic analysis were performed. Immunoblotting showed that the amplified band corresponding to ALFuc (~51 kDa) was recognized only in the ES/p. Furthermore, prediction analysis of ALFuc 3D structures revealed that the domain α-L-fucosidase and the GH29 family's catalytic sites were conserved; interestingly, the galactose-binding domain was recognized only in ST1 and ST2. The phylogenetic inferences of ALFuc showed that STs1–3 were clearly identifiable and grouped into specific clusters. Our results show, for the first time through experimental data that ALFuc is a secretion product of Blastocystis sp., which could have a relevant role during intestinal colonization; however, further studies are required to clarify this condition. Furthermore, the alfuc gene is a promising candidate for a phylogenetic marker, as it shows a conserved classification with the SSU-rDNA gene.

ABSTRACT Intestinal mucins are the first line of defense against microorganisms. Although knowledge about the mechanisms involved in the establishment of intestinal protozoa is limited, there is evidence that these parasites produce lectin-like molecules and glycosidases, that exert both, constitutive and secretory functions, promoting the establishment of these microorganisms. In the present review, we analyse the main interactions between mucins of the host intestine and the four main protozoan parasites in humans and their implications in intestinal colonization. There are lectin-like molecules that contain complex oligosaccharide structures and N-acetylglucosamine (GlcNAc), mannose and sialic acid as main components, which are excreted/secreted by Giardia intestinalis, and recognized by the host using mannose-binding lectins (MBL). Entamoeba histolytica and Cryptosporidium spp. express the lectin galactose/N-acetyl-D-galactosamine, which facilitates their adhesion to cells. In Cryptosporidium, the glycoproteins gp30, gp40/15 and gp900 and the glycoprotein lectin CpClec are involved in protozoan adhesion to intestinal cells, forming an adhesion-attack complex. G. intestinalis and E. histolytica can also produce glycosidases such as β-N-acetyl-D-glucosaminidase, α-d-glucosidase, β-d-galactosidase, β-l-fucosidase, α-N-acetyl-d-galactosaminidase and β-mannosidase. In Blastocystis, α-D-mannose, α-D-glucose, GlcNAc, α-D-fucose, chitin and sialic acid that have been identified on their surface. Fucosidases, hexosaminidases and polygalacturonases, which may be involved in the mucin degradation process, have also been described in the Blastocystis secretoma. Similarly, symbiotic coexistence with the intestinal microbiota promotes the survival of parasites facilitating cell invasion and nutrients obtention. Furthermore, it is necessary to identify and characterize more glycosidases, which have been only partially described by in silico analyses of the parasite genome.

The study described here was performed in a suburban community of the Estado de México to Echinococcus spp, since a human case of cystic echinococcosis (CE) was identified previously. Overall, 91% (406/446) of the houses were visited and oral informed consent was obtained from dog owners; a questionnaire related to their dogs was applied and a coprological sample was obtained. It was found that 14% of dog owners fed them with raw livestock viscera. Coprological studies showed that eggs of Ancylostoma and Toxocara were the most abundant, thus deworming was recommended to all owners. Dogs with Taenia spp eggs were treated and Taenia pisiformis adults were released, not from Echinococcus spp. Most sheep in the community were studied by ultrasound and viscera of those slaughtered, were visually inspected; confirming the absence of CE. Interestingly, although no evidences of Echinococcus spp were found in animals, an autochthonous human case of CE was detected in 2006; this, added to proper practices for maintaining the life cycle of this parasite, suggests that echinococcosis in Mexico has a random behavioral pattern.

El presente estudio se llevó a cabo en una comunidad suburbana del Estado de México para identificar Echinococcus spp, debido a que en un estudio previo se identificó un caso de equinococosis quística (EQ) humana. Se visitaron 91% (406/446) de las viviendas y se obtuvo el consentimiento verbal de los propietarios de perros; se aplicó un cuestionario relacionado con sus animales y se obtuvo una muestra de heces. Se encontró que 14% de los dueños de perros los alimentaban con visceras crudas de animales de abasto; este resultado no tuvo significancia estadística. Los estudios coprológicos mostraron abundantes huevos de Ancylostoma y Toxocara, por lo que se recomendó a los propietarios la desparasitación de sus animales. Aquellos perros que tenían huevos de Taenia spp fueron desparasitados y se recuperaron adultos de Taenia pisiformis, no de Echinococcus spp. La mayoría de los borregos de la comunidad se estudiaron por ultrasonido, y las visceras de aquéllos que fueron sacrificados se examinaron durante la necropsia; en ambos casos se confirmó la ausencia de EQ. Llama la atención que aunque no se encontraron evidencias de Echinococcus spp en animales, el antecedente de un caso humano autóctono de EQ, sumado a prácticas propicias para el mantenimiento del ciclo de vida de este parásito, sugieren que la equinococosis en México tiene un patrón de comportamiento aleatorio.