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Background: Blastocystis sp. is a common intestinal protozoan found worldwide. Based on gene analysis, 17 subtypes (STs, ST1-ST17) have been identified, 9 of which have been isolated from humans. Differences in clinical consequences may depend on differences among the STs. Here, we evaluated the prevalence of Blastocystis sp. in patients with colorectal cancer (CRC) compared to a control group and assessed the relationships between Blastocystis sp. infection and sex; age; and CRC grade, stage, and location., Methods: The study included 107 CRC patients (41 women and 66 men, median age 65 years); 124 subjects without colorectal cancer or a history of oncological disease comprised the control group (55 women and 69 men, median age 63). Stool samples were collected from patients before oncological treatment and examined using light microscopy (iodine-stained smear). Additionally, PCR-based identification of Blastocystis sp. was performed in 95 stool samples from CRC patients and 76 stool samples from the control group., Results: Light microscopy showed that the prevalence of Blastocystis sp. was significantly higher in CRC patients than in the control group (12.15% and 2.42%, respectively; p = 0.0041). Multivariate analysis showed that the odds of Blastocystis sp. infection were fivefold higher in the CRC group than in the control group. PCR-based molecular examinations demonstrated that the proportion of patients infected with Blastocystis sp. was significantly higher in the CRC group than in the control group (12.63% and 2.63%, respectively; p = 0.023). The predominant ST in the CRC group was ST3, detected in nine patients (75%), followed by ST1 (2 patients, 16.7%) and ST2 (1 patient, 8.3%). No association was found between Blastocystis sp. infection and age, sex, or CRC stage, grade, or location., Conclusions: The results showed that CRC was associated with an increased risk of opportunistic Blastocystis sp. infection, even before oncological treatment. To the best of our knowledge, this is the first report estimating the prevalence of Blastocystis sp. infection in CRC patients before oncological treatment in Europe.

Background: Infectious gastroenteritis is a risk factor for the development of post-infectious Irritable Bowel Syndrome (PI-IBS). Recent clinical studies reported a higher prevalence of the intestinal parasite Blastocystis in IBS patients. Using a rat model, we investigated the possible association between Blastocystis infection, colonic hypersensitivity (CHS), behavioral disturbances and gut microbiota changes., Methods: Rats were orally infected with Blastocystis subtype 4 (ST4) cysts, isolated from human stool samples. Colonic sensitivity was assessed by colorectal distension and animal behavior with an automatic behavior recognition system (PhenoTyper), the Elevated Plus Maze test and the Forced Swimming tests. Feces were collected at different time points after infection to study microbiota composition by 16 S rRNA amplicon sequencing and for short-chain fatty acid (SFCA) analysis., Results: Blastocystis-infected animals had non-inflammatory CHS with increased serine protease activity. Infection was also associated with anxiety- and depressive-like behaviors. Analysis of fecal microbiota composition showed an increase in bacterial richness associated with altered microbiota composition. These changes included an increase in the relative abundance of Oscillospira and a decrease in Clostridium, which seem to be associated with lower levels of SCFAs in the feces from infected rats., Conclusions: Our findings suggest that experimental infection of rats with Blastocystis mimics IBS symptoms with the establishment of CHS related to microbiota and metabolic shifts.

Cell structures morphologically consistent with Blastocystis were aspirated from a subcutaneous facial swelling in a 13-mo-old pet duck. On PCR analysis and sequencing, the organism was confirmed as Blastocystis sp. subtype 7. Blastocystis is a single-celled protist that is found in the intestinal tract of many species, including mammals, birds, reptiles, amphibians, and insects. A complete understanding of the lifecycle and pathogenesis of the parasite remains elusive. Blastocystis has been implicated in human and animal disease; however, its role is controversial given that it is commonly found among healthy gut microbiota. Infection with Blastocystis outside the intestinal tract has been reported only rarely in humans. Our case of subcutaneous Blastocystis infection in a duck is a novel presentation of a ubiquitous, generally asymptomatic, parasite or commensal of the intestinal tract.

Purpose: The present study aimed to determine the frequency of subtypes of Blastocystis sp. in the immunosuppressed individuals, in patients with chronic urticaria, and in patients with GIS complaints to investigate the difference of Blastocystis sp. subtype distribution between patient and control groups., Methods: A total of 345 stool samples were collected from the patients and samples were studied by native-Lugol, trichrome staining, and Jones medium culture method. Positively detected samples were subjected to PCR to determine the subtypes., Results: This is the first study of nine subtypes of Blastocystis sp. investigated in our country and the most frequently found subtype was ST3, and then, the other subtypes were ST1, ST2, ST5, and ST6, respectively. Mix subtype was detected in the 11.6% and no subtype was detected in the 17.4% of the samples. The ST5 was detected first time in the control group and ST6, which is reported limitedly in our country, was found in patients with GIS complaints. ST1 and ST2 were found higher in the patient group., Conclusion: This study confirmed that the subtype (ST) differences are an important factor affecting the pathogenesis of Blastocystis sp.

Blastocsytis sp. is a protozoan parasite that has been linked to common gastrointestinal illnesses. Metronidazole, the first line therapy, was reported to show frequent inefficacy. Previously, Blastocystis sp. isolated from different population showed varying metronidazole resistance. However, the effect of metronidazole treatment on pathogenic potentials of Blastocystis sp. isolated from different populations, which is known to have different gut environment, is unclear. This study investigates the in vitro effect of metronidazole on the pathogenic potentials of Blastocystis sp. isolated from urban and orang asli individuals. Blastocystis sp. ST 3 isolated from symptomatic and asymptomatic individuals were treated with a range of metronidazole concentration. The parasites' growth characteristics, apoptotic rate, specific protease activity and the ability to proliferate cancer cells were analyzed upon treatment with 0.001 mg/l metronidazole. The study demonstrates that Blastocystis sp. isolates showed increase in the parasite numbers especially the amoebic forms (only in urban isolates) after treating with metronidazole at the concentration of 0.001 mg/ml. High number of cells in post-treated isolates coincided with increase of apoptosis. There was a significant increase in cysteine protease of Blastocystis sp. isolates upon treatment despite the initial predominance of serine protease in asymptomatic isolates. Metronidazole resistant Blastocystis sp. also showed significant increase in cancer cell proliferation. Resistance to metronidazole did not show significant different influence on the pathogenicity between Blastocystis sp. isolated from urban and orang asli individual. However, an increase in parasite numbers, higher amoebic forms, cysteine protease and ability to proliferate cancer cells implicates a pathogenic role. The study provides evidence for the first time, the effect of metronidazole towards enhancing pathogenic potentials in Blastocystis sp. when isolated from different gut environment. This necessitates the need for reassessment of metronidazole treatment modalities., Competing Interests: The authors have declared that no competing interests exist.

In the reported case, a 41-year-old Italian man came to the clinician's observation reporting cramps, bloating and watery diarrhoea a few days after drinking water indicated as unpotable from a fountain in a farm area. The medical suspicion was directed at both gluten intolerance and enteric infection, eventually of waterborne origin. Gluten intolerance was investigated by intestinal biopsy and excluded, while stool analyses ruled out infective bacteriological or viral agents and parasites. Subsequently, a persistent eosinophilia was revealed and a parasitological analysis was again suggested, planning for a more sensitive molecular method. Therefore, a multiplex-PCR of enteric protozoa species DNA was performed on an intestinal biopsy and faecal samples revealing only Blastocystis hominis protozoa, subsequently typed as subtype 1 by RFLP-PCR method. B. hominis is an anaerobic protozoa found in the human and animal intestinal tract, recently associated with a pathogenic role characterized by chronic development. Since blastocystosis has been demonstrated as a waterborne infection, a sample of water matrix was analysed, revealing the B. hominis subtype 1 DNA inside. A probable water transmission of Blastocystis infection has been demonstrated in this case report. Only a probiotic treatment based on Saccharomyces boulardii was administered to the patient and this apparently resolved the infection. In summary, the case described here is a chronic blastocystosis of possible waterborne origin, controlled by assuming a yeast treatment.

Introduction: Lymphocytic colitis and microscopic enteritis are relatively common causes of chronic diarrhea and it is characterized by an intraepithelial lymphocytic infiltrate. There have been no previous reports of coexistence between these 2 pathologies., Objective: To describe histological and clinical characteristic in patients with coexistence of lymphocytic colitis and microscopic enteritis., Material and Methods: All cases with simultaneous diagnosis of lymphocytic duodenosis and lymphocytic colitis were reevaluated during lapse time 2010-2016 in hospital Daniel Carrion. The slides were reviewed by 3 pathologists and clinical information was obtained from clinical records. Expression of CD3 and CD8 was detected in 6 cases by immunohistochemical assays., Results: A total of 35 patients with coexistence of lymphocytic duodenitis and lymphocytic colitis were selected of the pathology archives, 80% were females, Anemia was identified in 28.5% of patients. Blastocysitis hominis infestation was identified in 31.8%. The mean intraepithelial lymphocyte CD8 and CD3 positive was 40% in microscopic enteritis, while the mean intraepithelial lymphocyte CD3 positive was 37.2% and CD8 positive was 29.2% Additionally, lymphocytic ileitis was diagnosed in 11 of our cases. Eosinophilic colitis was diagnosed in 9 cases of lymphocytic colitis Conclusion: We found that lymphocytic colitis, microscopic enteritis and even lymphocytic ileitis can coexist in a group of patients with chronic diarrhea. These findings bring the question if this concurrence of both pathologies constituted a more generalized gastrointestinal disorder, involving both the large and the small intestines.

Background/aims: The aim of this study was to determine the prevalence and significance of intestinal protozoa, specially Blastocystis spp., and to perform PCR-based subtype classification for understanding the importance of Blastocystis spp. in the pathogenesis of gastrointestinal disorders in post-traumatic splenectomized patients., Materials and Methods: A total of 60 stool samples were obtained from 30 post-traumatic splenectomized patients and 30 healthy controls. Wet mounts, trichrome and Kinyoun acid-fast stained slides were prepared from the stool specimens. PCR was used for detecting the presence of Giardia spp., Entamoeba spp., Dientamoeba fragilis, Cryptosporidium spp., Blastocystis spp. Genotyping was realized by using Blastocystis hominis STS primers., Results: In both study groups, any helminth eggs and other protozoa except Blastocystis spp. were not detected by microscopy and PCR, and also bacterial cultures were negative. Only stool microscopy was positive for Blastocystis spp. in 30% (9 of 30) of splenectomized patients and in 13% (4/30) of healthy controls. PCR for Blastocystis spp. was positive in 40% (12 of 30), B. hominis genotypes were 20% (6/30): STS1 in 10% (3/30) and STS3 in 10% (3/30) of splenectomized patients. In healthy controls Blastocystis spp. was 13% (4/30) by PCR and genotypes of B. hominis was not detected. The difference between the prevalence of Blastocystis spp. infection in splenectomized patients and control groups was statistically significant (p=0.020). Abdominal pain was the most frequent gastrointestinal symptom (p=0.019) among splenectomized patients positive for Blastocystis spp., Conclusion: In post-traumatic healthy splenectomized patients, Blastocystis spp. were found to be the most prevalent protozoa and may be responsible for the gastrointestinal disorders., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Blastocystis (initially named as Blastocystis hominis) has long been known as a protist without any clinical significance. However, there is now a huge pile of case reports where Blastocystis is blamed for the symptoms and the infection described in the patients. Introduction of the presence of as many as 17 Blastocystis subtypes while many infected individuals are non-symptomatic initially brought about the correlation between the subtypes and pathogenicity; however, the outcomes of these trials were not consistent and did not explain its pathogenicity. Today, it is mostly acknowledged that Blastocystis may colonize many individuals but the infection's onset depends on the interaction between the virulence of parasites and host's immune competence. Eradication of Blastocystis is essential in some cases where it is the only infectious agent and patient is suffering from some symptoms. In such cases, metronidazole is the drug of choice but its efficacy is relatively low in some cases. Other agents used include trimethoprim-sulfamethoxazole, paromomycin, and furazolidone. Recent studies on the interactions between human health and the role of gut microbiota introduces new data which may significantly change our point of view against some protists, which we tend to see as "parasites requiring urgent eradication for cure". May the presence or absence of some Blastocystis subtypes necessary for human health, or is the absence or presence of certain Blastocystis subtypes in human gut is associated with certain diseases/infections? The answers of these questions will surely guide us to select patients requiring treatment against Blastocystis infection in future., (Copyright © 2016. Published by Elsevier Ireland Ltd.)

Persistence activity manifested in the expression of anti-lysozyme, anti-lactoferrin, and antihistone factors promoting inactivation of natural anti-infection resistance factors in the body was revealed in Blastocystis hominis protozoa. Activities of these factors were ranged. The frequency of these factors in clinical isolates of blastocyst decreased in the following order: anti-lactoferrin activity (84.5±3.7%)→anti-lysozyme activity (64.8±5.7%)→anti-histone activity (48.1±2.3%). In healthy humans, the corresponding parameters were 7.3±1.3, 5.3±0.9, and 3.3±0.4%, respectively (p<0.05). It was shown that the studied activities in highly virulent blastocysts were higher than in groups of medium-, low-, and avirulent protozoa.

Introduction: Literature data provide little information about protozoa infections and gut microbiota compositional shifts in humans. This preliminary study aimed to describe the fecal bacterial community composition of people from Côte d'Ivoire harboring Giardia duodenalis, Entamoeba spp., and Blastocystis hominis, in trying to discover possible alterations in their fecal microbiota structure related to the presence of such parasites., Methodology: Twenty fecal samples were collected from people inhabiting three different localities of Côte d'Ivoire for copromicroscopic analysis and molecular identification of G. duodenalis, Entamoeba spp., and B. hominis. Temporal temperature gradient gel electrophoresis (TTGE) was used to obtain a fingerprint of the overall bacterial community; quantitative polymerase chain reaction (qPCR) was used to define the relative abundances of selected bacterial species/group, and multivariate statistical analyses were employed to correlate all data., Results: Cluster analysis revealed a significant separation of TTGE profiles into four clusters (p < 0.0001), with a marked difference for G. duodenalis-positive samples in relation to the others (p = 5.4×10-6). Interestingly, qPCR data showed how G. duodenalis-positive samples were related to a dysbiotic condition that favors potentially harmful species (such as Escherichia coli), while Entamoeba spp./B. hominis-positive subjects were linked to a eubiotic condition, as shown by a significantly higher Faecalibacterium prausnitzii-Escherichia coli ratio., Conclusions: This preliminary investigation demonstrates a differential fecal microbiota structure in subjects infected with G. duodenalis or Entamoeba spp./B. hominis, paving the way for using further next-generation DNA technologies to better understand host-parasite-bacteria interactions, aimed at identifying potential indicators of microbiota changes.

Blastocystis spp. are widely prevalent extra cellular, non-motile anerobic protists that inhabit the gastrointestinal tract. Although Blastocystis spp. have been associated with gastrointestinal symptoms, irritable bowel syndrome and urticaria, their clinical significance has remained controversial. We established an ex vivo mouse explant model to characterize adhesion in the context of tissue architecture and presence of the mucin layer. Using confocal microscopy with tissue whole mounts and two axenic isolates of Blastocystis spp., subtype 7 with notable differences in adhesion to intestinal epithelial cells (IEC), isolate B (ST7-B) and isolate H (more adhesive, ST7-H), we showed that adhesion is both isolate dependent and tissue trophic. The more adhesive isolate, ST7-H was found to bind preferentially to the colon tissue than caecum and terminal ileum. Both isolates were also found to have mucinolytic effects. We then adapted a DSS colitis mouse model as a susceptible model to study colonization and acute infection by intra-caecal inoculation of trophic Blastocystis spp.cells. We found that the more adhesive isolate ST7-H was also a better colonizer with more mice shedding parasites and for a longer duration than ST7-B. Adhesion and colonization was also associated with increased virulence as ST7-H infected mice showed greater tissue damage than ST7-B. Both the ex vivo and in vivo models used in this study showed that Blastocystis spp. remain luminal and predominantly associated with mucin. This was further confirmed using colonic loop experiments. We were also successfully able to re-infect a second batch of mice with ST7-H isolates obtained from fecal cultures and demonstrated similar histopathological findings and tissue damage thereby coming closer to proving Koch's postulates for this parasite.

Blastocystis is a genus of common single-celled intestinal parasitic protists with an unsettled role in human health and disease. Being a stable component of intestinal microbiota, once established, the Blastocystis parasite appears more common in healthy individuals than in patients with infectious, functional, or inflammatory bowel disease. Recent data suggest that the parasite is associated with certain gut microbiota profiles and health indices. Convincing data and tools differentiating asymptomatic colonization from infection are yet to be demonstrated. Although the parasite may elicit disease under certain circumstances, the focus on Blastocystis may be shifting from a clinical to a public health perspective., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Blastocystis is an ubiquitous, enteric protozoan of humans and many other species. Human infection has been associated with gastrointestinal disease such as irritable bowel syndrome, however, this remains unproven. A relevant animal model is needed to investigate the pathogenesis/pathogenicity of Blastocystis. We concluded previously that pigs are likely natural hosts of Blastocystis with a potentially zoonotic, host-adapted subtype (ST), ST5, and may make suitable animal models. In this study, we aimed to characterise the host-agent interaction of Blastocystis and the pig, including localising Blastocystis in porcine intestine using microscopy, PCR and histopathological examination of tissues. Intestines from pigs in three different management systems, i.e., a commercial piggery, a small family farm and a research herd (where the animals were immunosuppressed) were examined. This design was used to determine if environment or immune status influences intestinal colonisation of Blastocystis as immunocompromised individuals may potentially be more susceptible to blastocystosis and development of associated clinical signs. Intestines from all 28 pigs were positive for Blastocystis with all pigs harbouring ST5. In addition, the farm pigs had mixed infections with STs 1 and/or 3. Blastocystis organisms/DNA were predominantly found in the large intestine but were also detected in the small intestine of the immunosuppressed and some of the farm pigs, suggesting that immunosuppression and/or husbandry factors may influence Blastocystis colonisation of the small intestine. No obvious pathology was observed in the histological sections. Blastocystis was present as vacuolar/granular forms and these were found within luminal material or in close proximity to epithelial cells, with no evidence of attachment or invasion. These results concur with most human studies, in which Blastocystis is predominantly found in the large intestine in the absence of significant organic pathology. Our findings also support the use of pigs as animal models and may have implications for blastocystosis diagnosis/treatment.

We determined cytokines (e.g. interleukin-8, 10, 12 and TNF-α) expression by peripheral blood mononuclear cells (PBMCs) and in rectal mucosa in diarrhoea-predominant irritable bowel syndrome (D-IBS) with Blastocystis spp. Eighty patients with D-IBS and Blastocystis spp. infection were classified as 'cases' and 80 with D-IBS without Blastocystis spp. infection were classified as 'control'. Cases were subdivided into D-IBS and Blastocystis sp. defined type 1 (subtype-specific primer SB83) and type 3 (SB227). Stool microscopy and culture were performed. Rectal biopsies were obtained for histology and cytokines by real-time PCR for mRNA expression of cytokines. PBMCs IL-8 was similar in different groups but in type 1, IL-8mRNA was increased compared with type 3 (P = 0·001) and control (P = 0·001). In type 1, IL-10 by PBMCs had a low mean value (14·5±1·6) compared with (16·7±1·5) type 3 and (16±2·3) in controls (P<0·001 and P<0·001, respectively). In Blastocystis sp. type 1, low IL-10 was associated with lymphocyte and plasma cell infiltration (P = 0·015 and P = 0·002, respectively). In Blastocystis sp. type 1 and type 3, IL-12 was associated with goblet cell depletion 23 (85%) (P<0·001) and 8 (29%) (P = 0·037), respectively. In Blastocystis sp. type 1, low IL-10 was associated with a proinflammatory response characterized by IL-8.

Background: Blastocystis sp. is one of the most prevalent parasites found in human stool and has been recently considered an opportunistic emerging pathogen in immunocompromised individuals. However, cases of invasive intestinal infections and skin rashes have been attributed to infection by Blastocystis sp in immunocompetent individuals, suggesting that it is an emerging parasite with pathogenic potential., Findings: We present a case of a 22 year old female patient who complained of pain in the left hypochondrium. Ultrasonography and abdominal computed tomography scans showed two splenic cysts. The cyst fluid analysis demonstrated numerous Blastocystis sp.; PCR and DNA sequencing analyses confirmed the presence of Blastocystis subtype 3., Conclusions: This is, to our knowledge, the first case report of the presence of Blastocystis subtype 3 in extra-intestinal organs and is strong evidence that Blastocystis sp. is potentially pathogenic and invasive. However, further studies are required to determine the pathogenicity of the parasite.

The cases associated with the development of liver abscesses in a 64-year-old female patient after elective surgery for colon polyposis could form an opinion that extraenteric infection caused by Blastocystis spp. might develop in the immunocompromised host. The development of Blastocystis spp. in the presence of disintegrated liver tissue and inflammatory cells was verified by microscopic examination of liver abscess aspirates. The Romanovsky-Giemsa stained specimens exhibited typical amoeboid, vacuolar and, what is particularly important, dividing forms of Blastocystis spp. The patients full recovery after timely combination therapy with broad-spectrum antibiotics and imidazole group preparations also indirectly argues for the etiological role of Blastocystis spp. in the development of liver abscess with the signs of changes in both lungs (the signs of right lung compression and bilateral hydrothorax). Physicians' awareness of the potential clinical significance of Blastocystis spp. in immunodeficient patients is sure to expand the range of differential diagnostic studies of patients infected with Blastocystis spp.. particularly in case of gastrointestinal tract diseases of unknown etiology.

Blastocystis sp. is one of the most common parasites in the human intestinal tract. This infection commonly is accompanied by diarrhoea and abdominal pain, but extraintestinal symptoms, such as skin lesions, may also accompany the disease. In this study, our aim was to assess the frequency, clinical symptoms and skin manifestations of confirmed positive Blastocystis sp. infections. Data of 80 patients with confirmed positive Blastocystis sp. infections were assessed retrospectively. The average age of the patients was 46.3 years of age (with a range between 13 and 85 years of age). The number of female patients was higher than the number of males (48 vs. 32; 60 vs. 40%). Gastrointestinal and dermatological symptoms and the results of routine biochemical and haematological blood tests of enrolled patients were collected and analyzed. The skin manifestations were analyzed using the data available (including descriptions, photos and histologies). We discovered that 11.25% of our enrolled patients exhibited skin manifestations associated to Blastocystis sp., mainly on the females. The occurrence of Blastocystis sp. was 6% in symptomatic patients who required medical attendance in the time period between 2005 and 2013. Of the 80 patients, 73.75% indicated that they had gastrointestinal symptoms: 40 patients complained of abdominal pain and 17 with blood in their stool, while other symptoms, such as meteorism (15 subjects), weigh loss (8 subjects), perianal pain or itching (6 subjects), passing stool with mucus (5 subjects), vomiting (2 subjects) and fever (2 subjects) were less frequent. The prevalence of abdominal pain in the cohort without skin lesions was higher compared to those patients with skin problems (p = 0.007). The mean value of C-reactive protein showed elevated levels, but eosinophils were within a normal range. In addition, we did not find significant difference in eosinophilia between patients with vs. without skin manifestations. Thus, we suggest that eosinophilia is not an obligatory laboratory finding in protozoon infections, such as Blastocystis sp. In the light of our results, we suggest a stool parasite examination for patients with skin lesions of unknown origin.

Blastocytis sp. is the most common enteric protozoan in human, but its pathogenesis is still unclear. To study the infectious effects of Blastocytis sp. on tissue damage, we orally challenged the Sprague Dawley (SD) rats with different doses of Blastocytis subtype1 (ST1) and examined the histological changes. We found that there was no difference of disease incidence among the Blastocytis ST1-infected groups challenged with different doses of the protozoan. Histological results showed that the lamina propria was infected by Blastocytis ST1 in the vacuolar form, along with the mucus membrane slough and inflammatory cell infiltration into the lamina propria. Compared to the uninfected group, the histological scores were significantly higher in the infected groups. However, groups infected with various doses of Blastocystis ST1 showed no difference in terms of histological scores. In conclusion, this study indicates that the SD rats can be easily infected with Blastocytis ST1 even with low dose of cysts, and the histopathological effects of the infection in the intestine of the infected rats show individual differences.

Background: Blastocystis sp. has a worldwide distribution and is often the most common human intestinal protozoan reported in children and adults in developing countries. The clinical relevance of Blastocystis sp. remains controversial. This study was undertaken to determine the prevalence of Blastocystis infection and its association with gastrointestinal symptoms among outpatients in Sebha city, Libya., Methods: A total of 380 stool samples were collected from outpatients attending the Central Laboratory in Sebha, Libya for routine stool examination. The presence of Blastocystis sp. was screened comparing light microscopy of direct smears against in vitro cultivation. Demographic and socioeconomic information were collected with a standardized questionnaire., Results: The overall prevalence of Blastocystis infection was 22.1%. The prevalence was significantly higher among patients aged ≥18 years compared to those aged < 18 years (29.4% vs 9.9%; x² = 19.746; P < 0.001), and in males compared to females (26.4% vs 17.5%; x² = 4.374; P = 0.036). Univariate analysis showed significant associations between Blastocystis infection and the occupational status (P = 0.017), family size (P = 0.023) and educational level (P = 0.042) of the participants. Multiple logistic regression analysis confirmed that the age of ≥ 18 years (OR = 5.7; 95% CI = 2.21; 9.86) and occupational status (OR = 2.2; 95% CI = 1.02, 4.70) as significant predictors of Blastocystis infection among this population. In those who had only Blastocystis infection but no other gastrointestinal parasitic infections, the prevalence of gastrointestinal symptoms was higher compared to those without Blastocystis infection (35.3% vs 13.2%; x² = 25.8; P < 0.001). The most common symptoms among these patients were abdominal pain (76.4%), flatulence (41.1%) and diarrhoea (21.5%)., Conclusions: Blastocystis sp. is prevalent and associated with gastrointestinal symptoms among communities in Sebha city, Libya. Age and occupational status were the significant predictors of infection. However, more studies from different areas in Libya are needed in order to delineate the epidemiology and clinical significance of this infection.

The present study is aimed to identify the prevalence of Blastocystis subtypes isolated from patients in a major hospital in northeastern Thailand. A total of 562 stool samples were examined by culture technique, and 56 Blastocystis-positive samples were analyzed further by the combination of restriction fragment length polymorphism (RFLP) followed by polymerase chain reaction with sequence-tagged site primers (PCR-STS). By RFLP profiles, Blastocystis genotypes were categorized into four groups: group A (12, 21.4%), group B (32, 57.1%), group C (10, 17.9%), and group D (2, 3.6%). By PCR-STS, only four subtypes were identified. All 12 (21.4%) isolates in group A were identified as subtype 1. Similarly, all 32 (57.1%) isolates in group B were subtype 3. In group C, 10 (17.9%) samples were all subtype 7, and two samples (3.6%) in group D were both subtype 6. Of 56 Blastocystis-positive patients, 31 (55.4%) were asymptomatic and 22 (39.4%) have gastrointestinal symptoms. No significant association was observed between the Blastocystis subtypes and the clinical features. Among the Blastocystis-positive patients, the most characteristic stool samples were loose (78.6%) and soft (17.9%). In conclusion, the most common Blastocystis spp. in northeastern Thailand was subtype 3 followed by subtype 1. Relatively minor subtypes, subtype 6 and subtype 7 which are considered as avian subtypes, were found for the first time in humans in Thailand.

Blastocystis is one of the most common enteric parasites present in humans. There is still much uncertainty about the pathogenic potential of this parasite, and it was suggested that its pathogenicity could be subtype-related. This report aimed to study 98 Blastocystis isolates found in human stool specimens to identify the subtypes present and carry out phylogenetic analysis on these isolates. This study also aimed to show the relationship between subtype and symptoms. Five-hundred and thirteen stool samples were submitted to five different diagnostic techniques for the detection of Blastocystis. Polymerase chain reaction (PCR)-positive samples were then sequenced and the small subunit (SSU) rDNA sequences were aligned and submitted to phylogenetic analysis. Ninety-eight samples were positive by any of the diagnostic methods for Blastocystis and 96 were positive by PCR. There were seven different subtypes (1, 2, 3, 4, 6, 7 and 8) identified by PCR and sequencing. This is the first large-scale study to examine the occurrence of Blastocystis in Australia. This study reports the high incidence of subtype 3 (44 %) in this population and discusses the emerging idea of subtype-dependent pathogenicity.

Blastocystis is an unusual enteric protozoan parasite of humans and many animals whose pathogenic potential is still controversial. To increase the understanding of the molecular epidemiology of this emerging parasite and due to its potential impact on public health, its subtypes (STs) in Iranian symptomatic and asymptomatic individuals were determined. A total of 100 Blastocystis isolates by microscopy and culture methods were obtained. DNA was extracted from the positive culture isolates, and the Blastocystis subtypes were identified using seven subtype-specific sequenced-tagged site (STS) primers. Four subtypes, ST3 as dominant (53 %), followed by ST1 (48 %), ST5 (33 %), and ST2 (7 %) were identified. In this study, ST1 in gastrointestinal patients compared to asymptomatic individuals was significantly dominant (p = 0.001). From 33 (33 %) mixed subtype infections, ST1, 3 (14 %) was significantly related to GI symptoms (p = 0.045), and eight mixed infections with three different STs, which are under reported, were also identified.

Because of their limitations, current subtyping methods likely underestimate mixed human intra- and inter-subtype infections with Blastocystis sp. leading to erroneous data in the context of epidemiological studies. We confirmed this hypothesis by the identification of several isolates belonging to three subtypes in a patient considered at high risk of mixed infection through her lifestyle in rural area and long history of travelling., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

In this study, we collected data on the incidence of enteric parasites in healthcare-seeking individuals along with their symptoms to quantify the potential roles of factors such as age, sex, and seasonality in infection. We performed analysis to identify factors which could help differentiate parasitic infection from other causes of gastrointestinal illness in a community. The size of the patient population (n = 339), patient selection methodology, collection methods, and statistical analysis followed approaches from similar studies in core clinical journals. Ethical approval was obtained from the University of Karachi's Ethical Review Board. Fecal specimens (n = 339) submitted by symptomatic patients were collected from two clinical laboratories, along with information about the patients' age, sex, and symptoms. We found that symptoms of fever, vomiting, and constipation were 100 % predictive of finding a parasitic infection, while diarrhea was 88 % predictive of a parasitic infection. Gastrointestinal parasite-positive patients reported diarrhea (~60 %), vomiting (~30 %), fever (~25 %) and constipation (~25 %), while parasite-negative patients exhibited a symptomatic profile without fever, vomiting, and constipation. The distribution of symptoms in parasite-positive patients remained relatively invariant regardless of the parasite identified. Blastocystis spp.-mono-infected patients reported a similar profile to patients positive for Entamoeba histolytica/Entamoeba dispar and Cryptosporidium spp. Most parasitic infections exhibited a strong seasonal pattern, with a peak incidence in summer months. Infection by Blastocystis spp. was the most prevalent, and it was the only infection mathematically correlated to rainfall by Pearson's method. We observed no increase in healthcare-seeking behavior following a stressful community event, namely, the attempted assassination of Benazir Bhutto in Karachi. The data suggest that parasitological testing would produce a high yield of positive results when performed on healthcare-seeking patients in Karachi in 2007 with symptoms of fever, vomiting, or constipation and a low yield when performed on patients noting only abdominal pain. Parasitological testing also produces a higher yield on patients seen in summer months.

Introduction: Celiac disease (EC) not diagnosed or treated affect histological, immunological and nutritional status of patients who suffer it. These changes allow infection by parasites that cause no symptoms in immunocompetent patients, such as Blastocystis hominis (Bh). OBJETIVE. To analyze the presence of Bh in symptomatic celiac patients and describe the clinical, histological, immune and nutritional status in these patients. MATERIAL AND METHOD An observational descriptive cross sectional study was performed. Thirty symptomatic celiac patients (18 women, mean age 41 years old, range 19-68 years), assisted at the Institute of Gastroenterology of Cuba from January to December 2009, entered the study., Results: Diarrhea and chronic anemia were the most commonly reported clinical manifestations (22 and 4 patients, respectively). The analysis of more than five Bh per field was more frequent in the group ofpatients studied (63.3%), with statistically significant difference in patients with vilous atrophy and low weight (P < 0.03) compared to cases with less than five Bh per feld. No significant differences were found when the immune status of patients was analyzed. CONCLUSIONS. In symptomatic celiac patients with subtotal-total villous atrophy and low weight the finding of more than five Bh perfield should be considered as opportunistic.

Parasites in the genus Blastocystis comprise several subtypes (genotypes) and have a worldwide distribution. In some surveys, these are the most common parasites found in human stool specimens. An emerging literature suggests that the pathogenicity of Blastocystis is related to specific subtypes and parasite burden, although even individuals with small numbers of cysts may be symptomatic. Some data suggest an association between infection with Blastocystis and irritable bowel syndrome. However, there are few clinical studies demonstrating a direct relationship between the presence of this parasite and disease, few animal models to explore this relationship, and no consensus as to appropriate treatment. We recommend that asymptomatic individuals with few cysts not be treated. However, those who have gastrointestinal or dermatologic signs and symptoms and many cysts in stool specimens may require treatment. Metronidazole is the drug of choice. Additional studies are required to determine pathogenicity and appropriate therapy.

Despite accumulating evidence indicating that Blastocystis hominis is pathogenic and that cysteine proteases are involved in its pathogenesis, few researches discussed the protease activity of B. hominis genetic subtypes. Therefore, the present study aims to identify the underlying pathogenic role of the proteases of B. hominis subtype 3 at different molecular weights in correlation to gastrointestinal symptoms. Of 65 patients with various clinical presentations referred to our laboratory for stool examination, 26 (40%) were B. hominis positive by stool culture. Of 26 (group I) B. hominis patients, 18 (69.2%) were symptomatic (group IA) and 8(30.8%) were asymptomatic (group IB). Of 25 normal control group (group II), 5 (20%) were B. hominis positive. Subtype 3 was the only genotype recovered by polymerase chain reaction. Of 26 patients in group I, 19 (73.1%) were immunocompetent and 7 (26.9%) were immunocompromised. Protease activities of B. hominis subtype 3 were recognized at 32-kDa (46.2%), 39-kDa (7.7%), 120-kDa (38.5%), 140-kDa (11.5%), and 215-kDa (19.2%) bands in gelatin sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Proteases were recognized in 17 (94.4%) out of 18 symptomatic Blastocystis patients versus 2 (25.0%) out of 8 asymptomatic patients. Proteases at 32 kDa were reported in 61.1% of symptomatic versus 12.5% of asymptomatic patients. It was concluded that proteases of B. hominis genetic subtype 3, particularly those at 32 kDa, could be considered a virulence factor that is responsible for protein degradation and have a possible pathogenic role in host immune evasion.

Blastocystis is a common unicellular intestinal parasite in humans. Its clinical relevance is still subject to discussion with numerous conflicting reports on its ability to cause disease. A remarkable genetic heterogeneity among isolates suggests an association between distinct subtypes (STs) and pathogenicity, although a clear correlation between symptoms and subtype is lacking. Here, we report on a clinical case which possibly links Blastocystis sp. ST2 infection with the simultaneous occurrence of gastrointestinal illness and generalized chronic urticaria. Despite repeated chemotherapy with different antimicrobial drugs, both the gastrointestinal and cutaneous disorders reoccurred after short symptom-free intervals. Eradication of the parasite and permanent resolution of the patient's medical condition was finally achieved with the combined application of metronidazole and paromomycin.

Blastocystis hominis is a ubiquitous enteric protozoan whose pathogenic potential is still controversial. This study was carried out to clarify the pathogenecity of B. hominis infection and to study the proper number of parasites for mice infection. A total of 15 albino mice were orally inoculated with B. hominis and divided according to the inoculums, 10(2), 10(5), and 4 x 10(7) B. hominis forms/100 microl saline, into three groups consisting of five mice each, GI, GII GIII, respectively. In addition with group IV (uninfected control) consisting of five mice. All mice were sacrificed 2 weeks post-infection. The results revealed that all mice of GIII and two mice of GII got the infection while all mice of GI showed a completely negative result. Histopathological examination of large intestine on highly infected group (GIII) showed that B. hominis infiltrated the lamina propria, the submucosa, and the muscle layers in the form of collection of vacuolar forms. This was accompanied by active colitis with infiltration of mixed inflammatory cells. In conclusion, this study revealed that large number of B. hominis is essential for oral infection of mice and that vacuolar forms of B. hominis can invade the lamina propria, the submucosa, and even the muscle layers.

The fact whether Blastocystis hominis can invade has always been in question. Apart from a few sporadic studies such as that done on gnotobiotic guinea pigs which showed surface invasion and mucosal inflammation of the host's intestine caused by B. hominis infection, no real documentation of invasion has been proven. Studies have shown that hyaluronidase is secreted during the penetration into the host's skin and gut by nematode parasites. Hyaluronidase activity in protozoa namely Entamoeba histolytica has also been described previously. This study attempts to determine hyaluronidase in urine samples of B. hominis-infected rats. The presence of hyaluronidase in urine provides an indirect evidence of invasion by B. hominis into colonic epithelium causing the degradation of extracellular matrix proteins namely hyaluronic acid (HA). HA is depolymerized by hyaluronidase which may be used by organisms to invade one another. In this study, the levels of urinary hyaluronidase of Sprague-Dawley rats infected with B. hominis were monitored for 30 days. Hyaluronidase levels in the infected rats were significantly higher on days 28 and 30 compared to the day before inoculation (P < 0.01 and P < 0.05, respectively). During this stage, parasitic burden in infected stools was also at a high level. Proinflammatory cytokines, interleukin-6 and interleukin-8, were also significantly higher (P < 0.05) in the serum of infected rats. The study demonstrates that since no other pathogen was present and that amoeboid forms of the parasites have been shown to exist previously, the elevated levels of hyaluronidase in this preliminary finding suggests that the organism is capable of having invasion or penetration activity in the hosts' intestine.

Blastocystis is a polymorphic intestinal parasite that is common in humans. A total of 51 asymptomatic and symptomatic patients positive for Blastocystis only were included in the study. Symptoms were mainly nonspecific gastrointestinal symptoms. Blastocystis isolates were xenically cultured and subtyped. Blastocystis species subtype 3 was the predominant subtype. Intrasubtype differences (vacuolar/amoeboid presence) in subtype 3 morphotypes were observed in 32 asymptomatic and symptomatic subtype 3 cases and could possibly be related to Blastocystis pathogenic potential. Diverse morphologic features (vacuolar transiting to amoeboid), probably reflecting the progression from an asymptomatic to a symptomatic state, were observed in an asymptomatic subtype 3 carrier who later had symptoms. Searching for amoeboid forms might be helpful to presumptively screen symptomatic patients with subtype 3 or to follow up an asymptomatic subtype 3 carrier in case symptoms become evident before antiprotozoal treatment was attempted. Further studies on the roles of morphologic features and variation within Blastocystis species subtypes as predictors of symptoms are encouraged.

Despite years of study, the pathogenic role of Blastocytis hominis is still controversial. Genotypic differences between the asymptomatic and symptomatic isolates should assist in determining the pathogenicity of Blastocystis. In this study, we genotyped 32 Blastocystis isolates obtained from 12 asymptomatic healthy individuals and 20 symptomatic patients pain by polymerase chain reaction using known seven kinds of sequence tagged site primers in this study. When we compared genotype of Blastocystis isolates between the symptomatic and asymptomatic patient group, we found that subtype3 is the most dominant genotype in asymptomatic individual (9/12) and subtype1 determined all of symptomatic patients (20/20).

Blastocystis hominis is a zoonotic intestinal protozoan parasite whose pathogenic potential is still controversial. The aim of the present study was to clarify the pathogenicity of Blastocystis parasites in rats. Oral inoculation with 1 x 10(5) cysts of Blastocystis sp. strain RN94-9 in rats resulted in chronic infection in the cecum at least until 4 weeks after infection. Histological examination revealed neither mucosal sloughing nor inflammatory cell infiltration but showed a slight but significant increase in goblet cell numbers in the cecal mucosa 1-3 weeks post-infection. Differential staining of acidic and neutral mucins by the alcian blue-periodic acid-Schiff method showed that the predominantly increased cells were neutral mucin(+) but not acidic mucin(+) goblet cells. Reverse transcription real-time polymerase chain reaction studies demonstrated significant upregulation of the expression of interferon-gamma, interleukin (IL)-12, and tumor necrosis factor alpha, but not IL-6 or granulocyte-macrophage colony-stimulating factor, in the cecal mucosa at 2 and/or 3 weeks post-infection. The induction of local host responses, including mild goblet cell hyperplasia, and significant upregulation of type-1 and proinflammatory cytokines, suggest that Blastocystis sp. strain RN94-9 is a weakly pathogenic organism that could elicit proinflammatory as well as protective responses in local tissues.

Background: Blastocystis hominis is the most common parasite identified in s worldwide. Although it is commonly identified in stool preparations, unusual to encounter B hominis in abdominal fluid., Case: A 46-year-old woman presented with the clinical impression of acute peritonitis. The initial radiologic evaluation showed free air in the abdominal cavity and an abdominal mass. Abdominal fluid submitted for cytologic examination was diagnostic of acute inflammation with mixed bacteria and abundant cystlike forms of B hominis. The patient underwent an exploratory laparotomy that revealed a poorly differentiated adenocarcinoma involving her bowel and peritoneum., Conclusion: The present case highlights the unusual identification ofextraintestinal forms of B hominis in a peritoneal fluid sample from a patient with invasive, poorly differentiated adenocarcinoma and associated bowel perforation.

The effect of exogenous nitric oxide (NO) on growth, viability and ultra-structural of B. hominis was assessed in vitro by sodium nitrite (NaNO2) in 0.6 mM, 0.8 mM & 1 mM concentrations. The viability of B. hominis was identified using neutral red stain. The role of NO as an endogenous oxidant was assessed by identifying its level in cecum tissue, ileum tissue, blood and stool elutes of mice infected with B. hominis symptomatic human isolates using reactive nitrogen assay compared to control. In vitro study revealed that NaNO2 inhibited the growth and decreased viability of B. hominis with minimal lethal concentra-tion dose 1 mM on the 4th day while, minimal effects were detected with 0.6 and 0.8 mM. Transmission electron microscopy study proved that apoptotic-like features were observed in growing axenic culture of B. hominis upon exposure to NaNO2. These changes were not only found on the vacuolar (central body) form but also they were detected on granular, multi-vacuolar and cyst forms. In vivo study proved that high levels of NO were found in infected mice compared to low changes in control group. The high levels were in cecum tissue particularly. The mean levels of NO among infected mice were 211.8 +/- 20.7 microM in cecum, 90.4 +/- 11.6 microM in ileum, 60.1 +/- 4.7 microM in blood and 63.6 +/- 7.3 microM in stool elutes while, the mean levels of NO in control mice were 70.2 +/- 3.1 in cecum, 67.8 +/- 4.7 microM in ileum, 30.9 +/- 4.2 microM in blood and 28.1 +/- 2.9 microM in stool elutes. The differences were statistically highly significant. NO-donor drugs proved useful in treatment and increase the host resistance to B. hominis.

A total of 180 children of age group 5-12 years old in both sexes, of whom 90 were symptomatic and negative for other parasites, rotavirus or pathogenic bacteria. Another 90 children were asymptomatic, but with B. hominis in stools. Direct smear, formaline-ethyl acetate sedimentation concentration, kinyon carbol-fuchin stain, stool culture, enzyme immunoassay, culturing, morphometric study, gel electrophoresis and experimental infection of mice were done. The results showed that the central body cysts (CB), granular and multivacuolar forms isolated from symptomatic patients were larger than those from asymptomatic ones. The CB form was common compared to other forms and isolated from 104 cases. B. hominis infection was prevalent among males rather than females (60.5% versus 39.5%). The clinical data showed that diarrhea was the most common symptom (58.9%). The infection intensity had a direct relation with illness duration. The polyacrylamide gel electrophoresis showed that isolates from symptomatic and asymptomatic patients ranged between 24-130 kDa. All isolates showed similar banding patterns. Only minor differences was in low MW (30, 50 kDa) and in high MW (118 kDa) in samples from symptomatic patients. The histopathological examination of caecum, colon and small intestine of B. hominis mice infected from symptommatic patients showed infiltration with inflammatory cells and tissue invasion by the parasite.

The effect of exogenous administration of antioxidant (Anttox) on the course of B. hominis in experimentally infected mice was studied. B. hominis isolates were obtained from 10 gastrointestinal symptomatic adult patients. Three groups of 30 infected mice (3/isolate) were used. GI was untreated infected, GII was treated by antox for 4 weeks after infection diagnosis (treatment strategy), and GIII antox treated by for 4 weeks before infection (prophylactic strategy). Mild pathological changes were detected on 13.4%, 19.9% & 86.8% of mice in Gs I, II & III, respectively. Moderate pathological changes were found in 29.9%, 26.6% & 6.6% of mice in Gs I, II & III, respectively. While, the majority of severe pathological changes were in Gs I & II (56.7% & 53.5%) as compared to GIII (6.6%). Meanwhile, 86.8% of mice in GIII had B. hominis forms > 10/high power field compared to 3.3% in Gs I & II, respectively. Although 19.8% of mice in GII were positive for B. hominis by direct smear, no growth resulted in vitro and all the forms were non-viable by using neutral red stain. All the differences were statistically significant. So, antioxidant exacerbated B. hominis intensity but it decreased the pathological changes.

The aim of this study was to investigate the importance of the increase in intraepithelial lymphocytes (IELs) in the mucosa of the appendix. One hundred and four retrospective appendectomy specimens were examined to evaluate the IELs. Intraepithelial lymphocytosis was identified in 11.5% (12 cases) of the specimens. Of these 12 cases, 6 cases with intraepithelial lymphocytosis were associated with parasitic infection. No increase in IELs was found in the 36 appendices that were removed in other primary operations. A wide range of immunologic stimuli can raise IELs in the gastrointestinal system. However, in appendectomies with clinical signs of acute appendicitis, an increase in IELs is more likely to be related to parasitic infection. This increase should be considered for the diagnosis of parasitic infections.

Objective: To observe the ultrastructural change ot intestinal mucosa in mice infected with Blastocystis hominis, and to study the pathogenic mechanism of B. hominis infection., Methods: 20 Kunming mice were randomly divided into 4 groups: group A treated with immunosuppressant (dexamethasone), group B without immunosuppressant, group C as normal control and group D as immunosuppressant control. Groups A and B were then orally infected with 20(4) cysts of B. hominis. Groups C and D were treated as control by infusing same volume of Locke's solution. Six days after inoculation, mice in each group were killed and mucosa of ileocecum was observed by transmission electron microscope (TEM) and scanning electron microscope (SEM)., Results: Under SEM, B. hominis located in enteric cavity and on the surface of ileocecum mucosa. Individual parasites also invaded into mucosa and its fold. Partial destruction of microvilli on the mucosa was observed. TEM observation indicated a reduction of microvilli on the surface of absorptive cells. Mitochondrial edema, rough endoplasmic reticulum dilatation and degranulation were found on absorptive cells and goblet cells. Lymphocyte infiltration and eosinophilia were found in intercellular stroma. Pathological changes in group A were more serious than that of group B. No abnormal change on the mucosal ultrastructure was found in groups C and D., Conclusions: B. hominis infection causes significant ultrastructural lesion on the ileocecal mucosa in mice. Immune status of the mice can affect the degree of the lesion due to infection.

A 24-year-old woman had a 9-week history of second to third daily urticaria that began after an episode of contact urticaria to topical bufexamac. She was found to have an underlying gastrointestinal infection with Blastocystis hominis. This was thought to be clinically relevant as she had a history of mild chronic diarrhoea. After treatment of the Blastocystis hominis, her urticaria ceased. This could indicate the importance of performing stool microscopy and culture on all patients with chronic urticaria of unknown aetiology. The relationship of urticaria to intestinal parasites and the possibility that non-steroidal anti-inflammatory medications could act as cofactors that help precipitate an urticarial reaction is discussed.

Objective: To seek a better pathway and proper number of parasites for Blastocystis hominis (B.h) infection in normal and immunocompromised ICR mice., Methods: (1) 10(4), 10(5) and 10(6) B.h, cultured in RPMI 1640 medium from 3 generations were used to infect mice through oral and rectum; (2) 10(6) B.h were used to infect immunocompromised mice through rectum. The reproduction of B.h in gastrointestinal tract and the pathologic changes in the tissues were observed., Results: Mice were infected by B.h through either oral or rectum. The infected immunocompromised mice showed slow locomotion, depressed, lethargy, and descended body weight. Some infected mice discharged mucus feces, a few of them died during the experiment. Parasites were found in the whole gastrointestinal tract. Severe edema, hyperemia and congestion were observed in the tissues of jejunum, ileum, cecum and colon. The epithelia of small intestine and colonic mucous membrane showed exfoliation, inflammatory cell infiltration in submucosa, and structural changes in glands., Conclusion: Mice were more susceptible to Blastocystis hominis infection through rectum than orally. The parasites can be found in the whole gastrointestinal tract of mice, and can breed rapidly and cause significant pathological change in the gastrointestinal mucosa in immunocompromised mice.

Blastocystis hominis is now getting acceptance as an agent of human intestinal disease. B. hominis in stool samples of symptomatic and asymptomatic individuals was evaluated as a possible cause of gastro-intestinal troubles. B. hominis was found in 106 (10.1%) out of 1050 individuals examined from six villages and one city in Talkha Center, Dakahlia Governorate. The highest infection rate was in Manshayt El-Badawy village (25.47%), whereas Talkha City showed the lowest rate (4.73%). Age group 10-20 years had higher infection (13.3%). In twenty-three symptomatic patients, B. hominis represented the only causative parasitic agent. The most common symptoms were diarrhoea (30.4%), abdominal pain (26.1%), flatulence (21.7%). vomiting (13.1%) and fatigue (8.7%). High concentrations of B. hominis were found in symptomatic patients than in asymptomatic ones with statistical significant difference (8.2 cells/100 x field versus 3.8 respectively). The mean number of B. hominis was significantly high in patients complaining of diarrhoea and abdominal pain.

Ninety-nine individuals with stools positive for Blastocystis hominis but negative for other parasites were identified from medical records of healthy adults who had received a physical examination at Taipei Veterans General Hospital from November 2000 to October 2002. The medical records of these 99 positive cases and 193 randomly selected controls, matched for age, sex, and date of examination, were retrospectively reviewed. The pathogenicity of B. hominis could not be demonstrated due to a lack of association with the development of gastrointestinal symptoms or pathologic findings on endoscopic examination. Multivariate analyses revealed that chronic hepatitis B infection was a predisposing condition to the acquisition of B. hominis (odd ratio = 2.848, 95% confidence interval = 1.299-6.242, P = 0.009), and concentration of urate was significantly lower in B. hominis-positive individuals (mean +/- SD = 361.64 +/- 87.44 versus 392.57 +/- 93.38 micromol/L; P = 0.009). Among the 64 individuals who underwent gastric biopsy, Helicobacter pylori was found more frequently in the individuals harboring B. hominis (19 of 26 versus 15 of 38; P = 0.017).