Blastocystis hominis transmission by non-potable water: a case report in Italy.

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.

[Concurrent lymphocytic colitis and microscopic enteritis in patients with chronic diarrhea]. / Coexistencia de colitis linfocítica y enteritis microscópica en pacientes con diarrea crónica.

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.

Blastocystis in Health and Disease: Are We Moving from a Clinical to a Public Health Perspective?

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.

Characteristics of Factors of Protozoa Blastocystis hominis Persistence.

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.

Cytokine changes in colonic mucosa associated with Blastocystis spp. subtypes 1 and 3 in diarrhoea-predominant irritable bowel syndrome.

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.

Do not forget the stool examination!-cutaneous and gastrointestinal manifestations of Blastocystis sp. infection.

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.

[Extraenteric infection caused by Blastocystis spp. in a female patient with liver abscess].

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.

Subtype distribution of Blastocystis isolates identified in a Sydney population and pathogenic potential of Blastocystis.

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.

A rat model to study Blastocytis subtype 1 infections.

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.

Subtype identification of Blastocystis spp. isolated from patients in a major hospital in northeastern Thailand.

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: to treat or not to treat...

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.

Genetic variability of Blastocystis sp. isolated from symptomatic and asymptomatic individuals in Iran.

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.

Blastocystis spp., Cryptosporidium spp., and Entamoeba histolytica exhibit similar symptomatic and epidemiological patterns in healthcare-seeking patients in Karachi.

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.

[Blastocystis hominis in symptomatic celiac patients]. / Blastocystis hominis en pacientes celíacos sintomáticos.

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.

Proteaese activity of Blastocystis hominis subtype3 in symptomatic and asymptomatic patients.

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.

Colorectal cancer and Blastocystis sp. infection.

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.

Urinary hyaluronidase activity in rats infected with Blastocystis hominis--evidence for invasion?

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.

Pathogenic potential of Blastocystis hominis in laboratory mice.

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.

Fecal dysbiosis associated with colonic hypersensitivity and behavioral alterations in chronically Blastocystis-infected rats.

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.