Blastocystis infection has been reported to be associated with irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) and chronic diarrhoea. The availability of data on the subtypes of Blastocystis found in these patient groups would be of interest in understanding the significance of Blastocystis infection in chronic illness. In this study, we identify Blastocystis subtypes found in patients presenting with IBS, IBD, chronic diarrhoea and asymptomatic patients in Ankara, Turkey. Blastocystis was detected in 11 symptomatic patients by microscopy and 19 by stool culture. Stool culture was more sensitive than microscopy in identifying Blastocystis. Using standard nomenclature adopted in 2007, Blastocystis sp. subtype 3 was the most common in all groups, followed by Blastocystis sp. subtype 2. Identical subtypes of Blastocystis are found in patients with IBS, IBD and chronic diarrhoea. These particular subtypes show low host specificity and are carried by humans and some farm animals. The subtypes of Blastocystis that are commonly found in rodents and certain wild birds were not found in these patients. We suggest a model in which the severity of enteric protozoan infection may be mediated by host factors.

Blastocystis is the most common gastrointestinal protist found in humans and animals. Although the clinical significance of Blastocystis remains unclear, the organism is increasingly being viewed as a commensal member of the gut microbiome. However, its impact on the microbiome is still being debated. It is unclear whether Blastocystis promotes a healthy gut and microbiome directly or whether it is more likely to colonize and persist in a healthy gut environment. In healthy people, Blastocystis is frequently associated with increased bacterial diversity and significant differences in the gut microbiome. Based on current knowledge, it is not possible to determine whether differences in the gut microbiome are the cause or result of Blastocystis colonization. Although it is possible that some aspects of this eukaryote’s role in the intestinal microbiome remain unknown and that its effects vary, possibly due to subtype and intra-subtype variations and immune modulation, more research is needed to characterize these mechanisms in greater detail. This review covers recent findings on the effects of Blastocystis in the gut microbiome and immune modulation, its impact on the microbiome in autoimmune diseases, whether Blastocystis has a role like bacteria in the gut–brain axis, and its relationship with probiotics.

Introduction: The clinical significance ofBlastocystissp. andDientamoeba fragilisin patients with gastrointestinal symptoms is a controversial issue. Since the pathogenicity of these protists has not been fully elucidated, testing for these organisms is not routinely pursued by most laboratories and clinicians. Thus, the prevalence of these organisms and the subtypes ofBlastocystissp. in human patients in Turkey are not well characterized. This study aimed to determine the prevalence ofBlastocystissp. andD.fragilisin the diarrheic stool samples of immunodeficient and immunocompetent patients using conventional and molecular methods and to identifyBlastocystissp. subtypes using next generation sequencing.Material and methods: Individual stool specimens were collected from 245 immunodeficient and 193 immunocompetent diarrheic patients between March 2017 and December 2019 at the Gazi University Training and Research Hospital in Ankara, Turkey. Samples were screened forBlastocystissp. andD.fragilisby conventional and molecular methods. Molecular detection of both protists was achieved by separate qPCRs targeting a partial fragment of theSSUrRNA gene. Next generation sequencing was used to identifyBlastocystissp. subtypes.Results: The prevalence ofBlastocystissp. andD.fragiliswas 16.7% and 11.9%, respectively as measured by qPCR. The prevalence ofBlastocystissp. andD.fragiliswas lower in immunodeficient patients (12.7% and 10.6%, respectively) compared to immunocompetent patients (21.8% and 13.5%, respectively). FiveBlastocystissp. subtypes were identified and the following subtype distribution was observed: ST3 54.4% (n = 37), ST2 16.2% (n = 11), ST1 4.4% (n = 3), ST6 2.9% (n = 2), ST4 1.5% (n = 1), ST2/ST3 11.8% (n = 8) and ST1/ST3 8.8% (n = 6). There was no statistically significant difference in the distribution ofBlastocystissp. subtypes between immunocompetent and immunodeficient patients.Conclusion and recommendation: Our findings demonstrated thatBlastocystissp. andD.fragilisare commonly present in immunocompetent and immunodeficient patients with diarrhea. This study is the first to use next generation sequencing to address the presence ofBlastocystissp. mixed subtypes and intra-subtype variability in clinical samples in Turkey.

Purpose: To evaluate the in vivo efficacy of rose bengal (RB)-mediated photodynamic antimicrobial therapy (PDAT) for treatment of Acanthamoeba castellanii keratitis (AK). Materials and Methods: An animal (rabbit) AK model was successfully achieved via intrastromal inoculation of a suspension of A. castellanii cells and trophozoites. Prior to RB-PDAT (pre-treatment, day-5), the severity of the induced corneal infection was graded numerically for epithelial defects, stromal edema, neovascularity, and stromal opacity/infiltration. The right eyes of rabbits (n=18) were divided equally into three groups (n=6/group): control (no treatment); 0.1% RB+518 nm irradiation (5.4 J/cm²); and 0.2% RB+518 nm irradiation (5.4 J/cm²). On post-treatment day-5, animals were euthanized, after which corneal buttons were excised and submitted for real-time polymerase chain reaction (RT-PCR) analysis. Results: Post-treatment clinical scores of the 0.1 and 0.2% RB groups indicated significant improvement compared to control group scores (pre-treatment clinical scores; 5.17±0.98, 7.50±0.62, and 6.17±0.70 and post-treatment clinical scores; 4.50±0.56, (p=0.043), 3.50±0.99 (p=0.039), 6.83±1.66 (p=0.34), respectively). RT-PCR analysis revealed that the mean cycle threshold (Ct) values were significantly higher in treated-group corneas compared to control-group corneas, with no significant differences between treated-groups (Mean Ct values; 34.33, 34.5, and 29.67 for 0.1 and 0.2% RB, and control groups). There was a statistically significant negative correlation between post-treatment clinical scores and Ct values (r=-0.474, p-value 0.047). Conclusions: Our results demonstrate that RB-PDAT is effective in decreasing the parasitic load and clinical severity of AK.

Purpose: Cystic echinococcosis (CE) is caused by the larval form of Echinococcus granulosus. Clinical, radiologic, pathologic, and serologic findings should be evaluated together for the diagnosis of CE. The sensitivity and specificity oalf serologic tests may vary depending on the method used. In this study, we aimed to detect IgG antibodies specific to E. granulosus using indirect hemagglutination assay (IHA), enzyme-linked immunosorbent assay (ELISA), indirect fluorescent antibodies (IFA) and western blot (WB) tests. Methods: In our study, the serum samples of 74 patients sent to our laboratory with suspicion of CE were studied using two different commercial IHA tests, ELISA, IFA and WB test. The test results were evaluated along with radiological findings and histopathological examinations, the latter being the gold standard. Results: Of all the patients, 51 (69%) were female and 23 (31%) were male. There was a statistically significant difference between males and females (χ² = 9.7, p = 0.002). Out of 74 patients, positivity rates for Siemens IHA, Fumouze IHA, ELISA, IFA and WB test were positive as 33 (44.6%), 35 (47.3%), 43 (58.1%), 42 (56.7%) and 38 (51.3%), respectively. The sensitivity and specificity of the tests were as follows: 66.67 and 2.31% for Siemens IHA; 70.83% and 96.15% for Fumouze IHA; 85.42%, and 88.46% for ELISA; 83.33% and 88.46% for IFA; 72.92% and 88.46% for WB test. Conclusion: There were statistically significant differences in between all five methods (p < 0,001). While the tests with the highest specificity was Fumouze IHA, the test with the highest sensitivity was the ELISA test. It was concluded that IHA and ELISA tests were more practical in practice because of their greater applicability.