Blastocystis infection has been reported to be associated with irritable bowel syndrome (IBS)

Blastocystis hominis is one of the most common eukaryotic organisms in the intestinal tract of humans, while its pathogenic potential is still controversial. A total of 286 stool samples obtained from adult and pediatric patients with or without gastrointestinal symptoms in two hospitals in Manisa, Turkey, were cultured to detect B. hominis infection. Forty-one and 51 isolates were obtained from the adults and children, respectively, and these isolates were subjected to subtyping by polymerase chain reaction (PCR) with the known sequence-tagged site primers. The correlation between the genotype and the symptoms was evaluated. PCR subtyping indicated that subtype 3 was the most common genotype in both symptomatic and asymptomatic groups, and the second common genotype was subtypes 1 and 2 in symptomatic and asymptomatic groups, respectively. A significant correlation between subtype 2 and the asymptomatic groups was found among both in pediatric and adult patients (chi(2) (cal) = 4.38, df = 1, p = 0.044). However, there were no significant differences between the other genotypes and the symptomatic or asymptomatic groups, as well as both the age and sex of the patients. The present study suggests that subtype 2 is a non-pathogenic genotype of B. hominis.

BackgroundThis study compared diagnostic methods for identifying Blastocystis in stool samples, and evaluated the frequency of detection of Blastocystis in patients with irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).Results and DiscussionFrom a set of 105 stool specimens submitted for routine parasitological analysis, 30 were identified as positive for Blastocystis by the culture method. From that group of 30 positives, Lugol's stain, trichrome staining, and an immunofluorescence assay identified 11, 15, and 26 samples as positive respectively. Using culture as a standard, the sensitivity of Lugol's stain was 36.7%, trichrome staining was 50%, and the IFA stain was 86.7%. The specificity of Lugol's stain was 91%, trichrome staining was 100%, and the IFA stain was 97.3%. In the group of 27 IBS and IBD patients, using all methods combined, we detected Blastocystis in 67% (18/27) of the patients. Blastocystis was detected in 33% (2/6) of IBD patients and 76% (16/21) of IBS patients. For comparison, trichrome staining alone, the method most frequently used in many countries, would have only identified Blastocystis infection in 29% (6/21) of the IBS patients. No parasitic co-infections were identified in the IBS/IBD patients. Most Blastocystis-positive IBS/IBD patients were over 36 with an average length of illness of 4.9 years.ConclusionsMost IBS patients in this study were infected with Blastocystis. IFA staining may be a useful alternative to stool culture, especially if stool specimens have been chemically preserved.

Blastocystis sp. is now recognized as one of the most common intestinal parasite in human fecal examinations. Recently, PCR-based diagnostic methods of Blastocystis infection using direct DNA extraction from fresh fecal samples with commercially available kits are reported. Several kits have been developed, but little has been done in comparing the detective sensitivity between PCR methods using the commercial kits. In this study, we compared the detective sensitivity among five commercially available kits (MagNA Pure LC DNA Isolation Kit I, Roche; QuickGene SP Kit DNA, FujiFilm; NucleoSpin Plant II, Macherey-Nagel; QIAamp DNA Stool Mini Kit, Qiagen; ZR Fecal DNA Kit, Zymo Research) and fecal culture method. In a preliminary test, the DNA isolated with two kits (FujiFilm and Macherey-Nagel) showed negative PCR, while the other three kits showed positive PCR. Then, DNA from 50 clinical samples that was Blastocystis-positive in the examination of fecal culture method were isolated with the three kits and 1.1 kbp SSU rRNA gene was detected with PCR. The positive rates of the three kits (Roche, Qiagen, and Zymo Research) were 10, 48 and 94%, respectively. The present study indicated that there is different detective sensitivity among the commercial kits, and fecal culture method is superior in detection rate and cost performance than DNA-elution kits for diagnosis of Blastocystis sp. subtypes.

Introduction The clinical significance of Blastocystis sp. and Dientamoeba fragilis in 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 of Blastocystis sp. in human patients in Turkey are not well characterized. This study aimed to determine the prevalence of Blastocystis sp. and D. fragilis in the diarrheic stool samples of immunodeficient and immunocompetent patients using conventional and molecular methods and to identify Blastocystis sp. 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 for Blastocystis sp. and D. fragilis by conventional and molecular methods. Molecular detection of both protists was achieved by separate qPCRs targeting a partial fragment of the SSU rRNA gene. Next generation sequencing was used to identify Blastocystis sp. subtypes. Results The prevalence of Blastocystis sp. and D. fragilis was 16.7% and 11.9%, respectively as measured by qPCR. The prevalence of Blastocystis sp. and D. fragilis was lower in immunodeficient patients (12.7% and 10.6%, respectively) compared to immunocompetent patients (21.8% and 13.5%, respectively). Five Blastocystis sp. 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 of Blastocystis sp. subtypes between immunocompetent and immunodeficient patients. Conclusion and recommendation Our findings demonstrated that Blastocystis sp. and D. fragilis are commonly present in immunocompetent and immunodeficient patients with diarrhea. This study is the first to use next generation sequencing to address the presence of Blastocystis sp. mixed subtypes and intra-subtype variability in clinical samples in Turkey.