Blastocystosis: a new disease in the acquired immunodeficiency syndrome?

A Simple Genotyping Method for Rapid Differentiation of Blastocystis Subtypes and Subtype Distribution of Blastocystis spp. in Thailand

Blastocystis spp. is one of the most common protozoa of humans and animals worldwide. The genetic diversity of Blastocystis spp. might be associated with a wide range of symptoms. However, the prevalence of each subtype is different in each country. Until now, there is no standard method for subtyping of Blastocystis spp. We developed a sequential restriction fragment length polymorphism (RFLP) analysis for the rapid differentiation of human Blastocystis subtypes. A large-scale study was also conducted to determine the subtype distribution of Blastocystis spp. in Thailand. Stool samples were collected from 1025 school-age students in four regions of Thailand. Blastocystis infections were identified by direct smear, formalin ethyl-acetate concentration technique (FECT), Boeck and Drbohlav’s Locke-Egg-Serum (LES) medium culture, and polymerase chain reaction (PCR) of small-subunit ribosomal DNA (SSU rDNA). Subtypes of Blastocystis spp. were determined by RFLP. Phylogenetic tree of partial SSU rDNA sequences of Blastocystis spp. was constructed using the Maximum Likelihood (ML) method. Out of 1025 students, 416 (40.6%) were positive for Blastocystis spp. Using two steps of RFLP reactions, we could determine subtype one–three among these students. Subtype 3 was the most common subtype (58.72%) in Thai students, followed by subtype 1 (31.2%), and subtype 2 (10.1%). Blastocystis subtype 3 was the most prevalent in all regions of Thailand. The subtype distribution of Blastocystis spp. in Thailand was different from other countries.

Degradation of human secretory immunoglobulin A by Blastocystis

Microbial immunoglobulin A (IgA) proteases cleave human secretory IgA, promoting the mucosal adhesion of pathogens. To investigate if the enteric protozoan Blastocystis degrades human secretory IgA, cell lysate and conditioned medium from two species were exposed to immunoglobulin A. Secretory IgA was cleaved by both cell lysate and conditioned medium with mainly cysteine proteinase activity in B. hominis B isolate and aspartic proteinase activity in B. ratii WR1 isolate. These findings suggest that Blastocystis proteases may play a role in parasite survival in vivo.

No correlation between clinical symptoms and Blastocystis hominis in immunocompetent individuals

Abstract Background and Aim: Previous reports regarding the clinical significance and pathogenicity of Blastocystis hominis have been contradictory. The aim of this study was to examine the association between Blastocystis and gastrointestinal symptoms in immunocompetent individuals.

METHODS

We monitored over 2800 healthy people for a period of 15 months, and took stool specimens during both asymptomatic periods and during periods of gastrointestinal symptoms.

RESULTS

After exclusion of individuals who had simultaneous identification of other fecal pathogens, we compared the proportions of asymptomatic versus symptomatic individuals positive for Blastocystis and found no significant difference (P = 0.5). Symptom status did not correlate with parasite abundance. We found that some individuals were likely to have Blastocystis detected during both asymptomatic and symptomatic periods, possibly suggesting carriage of the organism.

CONCLUSION

In conclusion, we found no correlation between clinical symptoms and the presence or absence of Blastocystis among this healthy cohort.

Blastocystis hominis revisited

Blastocystis hominis is a unicellular organism found commonly in the intestinal tract of humans and many other animals. Very little is known of the basic biology of the organism, and controversy surrounds its taxonomy and pathogenicity. There morphological forms (vacuolar, granular, and ameboid) have been recognized, but recent studies have revealed several additional forms (cyst, avacuolar, and multivacuolar). The biochemistry of the organism has not been studied to any extent, and organelles and structures of unknown function and composition are present in the cells. Several life cycles have been proposed but not experimentally validated. The form used for transmission has not been defined. Infections with the organism are worldwide and appear in both immunocompetent and immunodeficient individuals. Symptoms generally attributed to B. hominis infection are nonspecific, and the need for treatment is debated. If treatment appears warranted, metronidazole is suggested as the drug of choice, although failures of this drug in eradicating the organism have been reported. Infection is diagnosed by light microscopic examination of stained smears or wet mounts of fecal material. Most laboratories identify B. hominis by observing the vacuolar form, although morphological studies indicate that other forms, such as the cyst form and multivacuolar form, also should be sought for diagnosis.

Occurrence of blastocystis sp. in cattle in Aragón, northeastern Spain

The occurrence of Blastocystis sp. in cattle is reported herein for the first time in Spain. Stool samples from 554 bovines ranging from 3 days old to adults collected from 30 cattle farms in Aragón (northeastern Spain) were concentrated by the formalin-ethyl acetate method and examined light microscopically for the presence of gastrointestinal parasites. Vacuolated cells of Blastocystis sp. was detected in fecal specimens from 10 calves (1.8%) aged from 7 weeks to 6 months. Infected calves were detected at 3 of the 30 farms surveyed (10%). Blastocystis sp. cells were rounded or oval, with a diameter ranging from 6.25 to 15 microns. Blastocystis infection in cattle was never correlated with diarrhea, although infection intensities were generally low.

Blastocistosis y otras infecciones por protozoos intetinales en comunidades humanas ribereñas de la cuenca del rio Valdivia, Chile

Entre marzo y octubre de 1987 se examinaron muestras coprológicas de 970 personas (20, 9% de la población) pertenecientes a 209 grupos familiares de las comunidades ribereñas de la cuenca del rio Valdivia, Chile; con el propósito de determinar las prevalencias de infección por Blastocystis hominis y otros protozoos intestinales para establecer relaciones con la edad y sexo de los hospedadores, saneamiento ambiental y porcentaje de individuos infectados por grupo familiar. Un 72, 5% de las personas presentó una o más especies de protozoos intestinales. La mayor prevalencia se registró para B. hominis (61, 8%), que se incrementó con la edad del hospedador al igual que en las infecciones por Endolimax nana y Entamoeba coli. No se demostró asociación entre el sexo del hospedador y la prevalencia de infección por B. hominis y otras especies de protozoos. La prevalencia de B. hominis fue mayor en individuos que habitaban viviendas cuya disposition de excrementos era no sanitaria. Más del 60% de los integrantes de los grupos familiares presentaron infección por B. hominis en el 53, 1% de las familias encuestadas en contraposición al 2,4%-21,8% observado en infecciones por otros protozoos. El examen de 45 muestras de excrementos de cerdos, reveló infección por Blastocystis en el 22,2% de estos animales.

Blastocystis hominis may be a potential cause of intestinal disease

Blastocystis hominis is a common inhabitant of the human bowel. It is now increasingly recognized as a potential cause of diarrhea. This article presents 12 cases of prolonged or recurrent diarrhea associated with B. hominis found in a large number. No other intestinal parasites were recognized. All patients responded to metronidazole. This report confirms that B. hominis may be a cause of intestinal disease.