Blastocystis hominis is a foodborne protozoan found in the human feces worldwide. One hundred and ninety-nine individuals with stool samples positive for B. hominis were identified from a pool of 14,325 patient stools collected between 2003 and 2010 from Srinagarind hospital in Thailand. The medical records of patients were reviewed for demographic and clinical data. Of the 85 patients (42.7%) who had B. hominis infection with no co-infections, 42.5% experienced gastrointestinal symptoms. Abdominal pain is the most frequently observed symptom followed by diarrhea. Strongyloides stercolaris and Opisthorchis viverrini were the predominant parasitic co-infections in blastocystosis patients. The infection rates of B. hominis were high during the rainy season. Most B. hominis-infected patients (94%) had underlying diseases; malignancy and chronic diseases were equally top ranked (35.3%) which indicated that B. hominis is an opportunistic protozoan.

Blastocystosis is a frequent bowel disease. We planned to to evaluate the prevalence of Blastocystis spp. in patients who applied to the same internal medicine-gastroenterology clinic with or without gastrointestinal complaints to reveal the association of this parasite with diagnosed IBS and IBD.A total of 2334 patients with gastrointestinal symptoms composed the study group, which included 335 patients with diagnosed inflammatory bowel disease and 877 with irritable bowel syndrome. Patients without any gastrointestinal symptoms or disease (n = 192) composed the control group. Parasite presence was investigated by applying native-Lugol and formol ethyl acetate concentration to stool specimens, and trichrome staining method in suspicious cases.Blastocystis spp. was detected in 134 patients (5.74%) in the study group and 6 (3.12%) in the control group (p = 0.128). In the study group, Blastocystis spp. was detected at frequencies of 8.7% in ulcerative colitis (24/276), 6.78% in Crohn's disease (4/59), 5.82% in irritable bowel syndrome (51/877), and 4.9% in the remaining patients with gastrointestinal symptoms (55/1122). Blastocystis spp. was detected at a statistically significant ratio in the inflammatory bowel disease (odds ratio [OR] = 2.824; 95% confidence interval [CI]: 1.149-6.944; p = 0.019) and ulcerative colitis (OR = 2.952; 95% CI: 1.183-7.367; p = 0.016) patients within this group compared to controls. There were no statistically significant differences between the control group and Crohn's disease or irritable bowel syndrome patients in terms Blastocystis spp. frequency (p = 0.251, p = 0.133).Blastocystosis was more frequent in patients with inflammatory bowel disease, especially those with ulcerative colitis. Although symptomatic irritable bowel syndrome and Crohn's disease patients had higher rates of Blastocystis spp. infection, the differences were not significant when compared to controls.

Blastocystis sp. is a common intestinal parasite found in humans and animals. The possibility of zoonotic transmission to humans from livestock especially goats led us to investigate the genetic diversity of caprine Blastocystis sp. obtained from five different farms in Peninsular Malaysia. Moreover, there is a lack of information on the prevalence as well as genetic diversity of Blastocystis sp. in goat worldwide. Results showed that 73/236 (30.9 %) of the goats were found to be positive for Blastocystis infection. The most predominant Blastocystis sp. subtype was ST1 (60.3 %) followed by ST7 (41.1 %), ST6 (41.1 %), and ST3 (11.0 %) when amplified by PCR using sequenced-tagged site (STS) primers. Four farms had goats infected only with ST1 whereas the fifth showed mixed infections with multiple STs. The proximity of the fifth farm to human dwellings, nearby domesticated animals and grass land as opposed to a sterile captive environment in the first four farms may account for the multiple STs seen in the fifth farm. Since ST1, ST3, ST6 and ST 7 were previously reported in human infection worldwide in particular Malaysia, the potential of the zoonotic transmission of blastocystosis should not be disregarded. The implications of different farm management systems on the distribution of Blastocystis sp. STs are discussed.

Blastocystis sp. is one of the most common intestinal protozoa in humans. Unlike other intestinal parasitic infections such as giardiasis and cryptosporidiosis, the epidemiology of blastocystosis in children who live in crowded settings such as day-care centers and orphanages has been rarely explored.A retrospective cohort study was conducted to evaluate incidence and risk factors of Blastocystis infection in an orphanage every two consecutive months during April 2003 to April 2004, in Bangkok, Thailand. Blastocystis sp. was identified using direct simple smear, and in vitro cultivation in Jones' medium.The incidence rate was 1.8/100 person-months and the independent risk factors associated with Blastocystis infection were age, nutritional status and orphans living in the room where their childcare workers were infected.Person-to-person transmission was most likely to occur either from orphans to childcare workers or from childcare workers to orphans living in the same room. Universal precautions such as regular hand washing and careful handling of fecally contaminated materials are indicated.

The pathogenic role of Blastocystis hominis is still regarded by some as controversial. Studies have been in progress for years to evaluate the role of blastocystosis in irritable bowel syndrome (IBS) and demonstrated that faecal carriage of B. hominis was frequent in these patients. This study attempted to distinguish different genotypes of B. hominis isolates obtained from patients with IBS and to evaluate their pathogenic potentials.One hundred subjects (51 patients with IBS and 49 asymptomatic infected subjects) harbouring B. hominis were investigated by a direct smear examination and in vitro culture of stool samples followed by genotyping of B. hominis by PCR using STS primers. Sigmoidoscopy was done in all subjects and biopsies were taken and subjected to histopathologic examination.Genotyping proved that only four genotypes of B. hominis were identified. In patients with IBS, genotypes III, I, and IV were detected (28, 15 and 14 isolates, respectively). On the other hand, genotypes III, IV, and II were identified in asymptomatic infected individuals (21, 19 and 13 isolates, respectively). The degrees of chronic inflammatory changes in sigmoidoscopic biopsies caused by B. hominis genotypes among IBS patients revealed that severe inflammation was present mainly in patients harboring genotype I isolates (4/15) (26.66%), while genotype III caused severe inflammation only in 9.09%. Genotype II isolates were not detected in IBS cases. Asymptomatic infected individuals harboring genotypes II, III and IV exhibited mild to moderate inflammatory changes. Genotype I isolates were not detected in asymptomatic infected group. The correlation between different B. hominis genotypes and degree of inflammation was statistically insignificant.Genotype I was the most pathogenic genotype of B. hominis isolates in patients with IBS while genotype II was not detected among those patients. Also, our results suggest the presence of pathogenic and non-pathogenic strains among genotypes III and IV.

Blastocystis hominis is a common protozoan in the human intestinal tract and can cause the so-called blastocystosis characterized by diarrhea. To date, its identification has depended on the discovery of vacuolar, granular, amoebic, or cystic forms in stool samples using wet mount smears, iodine staining, trichrome staining, or iron hematoxylin staining. The permanent staining methods provide more positive findings. However, mercuric chloride (HgCl(2))-based polyvinyl alcohol (PVA) and Schaudinn fixative are potentially toxic and dangerous to laboratory personnel and, as hazardous chemicals, present problems with disposal.To determine whether in vitro culture could be an environmentally safe alternative, the culture growth of B. hominis in three commercially available liquid media (RPMI 1640, 199 Medium, and Dulbecco's modified Eagle's medium (DMEM)) were observed and compared. The sensitivity and specificity of these culture methods to identify B. hominis were compared with those of existing methods used clinically.Conditions for the anaerobic culture of B. hominis in these media were determined as follows: total inoculum sizes no less than 10(5) cells; pH values ranging from 7.0 to 7.5; concentrations of calf or horse serum ranging from 10% to 30% (vol/vol); basic antibiotics added; peaking times at days 3, 6, and 9 (pH 7.5) or days 4 and 8 (or 9) (pH 7.0) at 37°C. No significant differences were noted in multiplication or generation times for the cultivation of B. hominis (p>0.05). In 56 of 398 positive cases, the short-term in vitro culture method achieved the best performance with regard to sensitivity and specificity of the five studied methods.With the advantages of environmental safety, convenience in preparation and storage, facility in morphologic discrimination, and outstanding performance in terms of sensitivity and specificity, the in vitro culture method could be applied to identify B. hominis for both clinical diagnosis and field study purposes.

Blastocystis is an enteric protistan parasite of uncertain clinical relevance. Recent studies indicate that the parasite is a species complex and humans are potentially hosts to nine Blastocystis subtypes, most of which are zoonotic. Subtype 3 is the most common in prevalence studies, followed by subtype 1. Laboratory diagnosis is challenging; the currently recommended diagnostic approach is trichrome staining of direct smears coupled with stool culture. Polymerase chain reaction testing from stools or culture is useful for determining Blastocystis subtype information. The controversial pathogenesis of Blastocystis is attributed to subtype variations in virulence; although current studies seem to support this idea, evidence suggests other factors also contribute to the clinical outcome of the infection. Clinical signs and symptoms of blastocystosis include abdominal pain, diarrhea, bloating, and flatulence. Extraintestinal manifestations, predominantly cutaneous, also were reported. In vitro and animal studies shed new light on the pathobiology of Blastocystis.

The present study was performed to characterize the protein profiles of Blastocystis hominis isolates from symptomatic and asymptomatic individuals by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting using sera from symptomatic and asymptomatic patients. The presence of immunogenic bands associated with pathogenicity or of diagnostic potentials was also evaluated. The study comprised 80 individuals classified into four groups, 20 each: symptomatic blastocystosis (G1), asymptomatic blastocystosis (G2), other parasitic infections (G3), and healthy control subjects (G4). SDS-PAGE analysis of individual antigens form symptomatic and asymptomatic B. hominis isolates revealed similar and distinctive antigenic bands with significant differences in two high (123.5 and 112.3 kDa) and few low molecular weight bands (48.5, 38, 42.3, and 35.5 kDa). Immunoblotting was performed using symptomatic and asymptomatic antigen pools with sera of the four studied groups. It was found that anti-B. hominis IgG reacted with nine protein bands ranging from 100 to 18 kDa of the symptomatic antigen pool. There was a significant difference between G1 and G2 in the recognition of 64, 56, 38, and 29 kDa antigen bands. Also, anti-B. hominis IgG reacted with five protein bands ranging from 56 to 12 kDa of asymptomatic antigen pool. There was a significant difference between G1 and G2 in the recognition of 29 kDa antigen band. These findings suggest the potential use of the 29-kDa antigen as marker of pathogenicity and implicate its use in the diagnosis and differentiation between symptomatic and asymptomatic blastocystosis.

Blastocystis hominis is one of the most common intestinal protozoan parasites in humans, and reports have shown that blastocystosis is coupled with intestinal disorders. In the past, researchers have developed an in vitro model using B. hominis culture filtrates to investigate its ability in triggering inflammatory cytokine responses and transcription factors in human colonic epithelial cells. Studies have also correlated the inflammation by parasitic infection with cancer. The present study provides evidence of the parasite facilitating cancer cell growth through observing the cytopathic effect, cellular immunomodulation, and apoptotic responses of B. hominis, especially in malignancy. Here we investigated the effect of solubilized antigen from B. hominis on cell viability, using peripheral blood mononuclear cells (PBMCs) and human colorectal carcinoma cells (HCT116). The gene expressions of cytokines namely interleukin 6 (IL-6), IL-8, tumor necrosis factor alpha, interferon gamma, nuclear factor kappa light-chain enhancer of activated B cells (a gene transcription factor), and proapoptotic genes namely protein 53 and cathepsin B were also studied. Results exhibited favor the fact that antigen from B. hominis, at a certain concentration, could facilitate the growth of HCT116 while having the ability to downregulate immune cell responses (PBMCs). Therefore, there is a vital need to screen colorectal cancer patients for B. hominis infection as it possesses the ability to enhance the tumor growth.