Blastocystis is a prevalent enteric protozoan that infects a variety of vertebrates. Infection with Blastocystis in humans has been associated with abdominal pain, diarrhea, constipation, fatigue, skin rash, and other symptoms. Researchers using different methods and examining different patient groups have reported asymptomatic infection, acute symptomatic infection, and chronic symptomatic infection. The variation in accounts has lead to disagreements concerning the role of Blastocystis in human disease, and the importance of treating it. A better understanding of the number of species of Blastocystis that can infect humans, along with realization of the limitations of the existing clinical laboratory diagnostic techniques may account for much of the disagreement. The possibility that disagreement was caused by the emergence of particular pathogenic variants of Blastocystis is discussed, along with the potential role of Blastocystis infection in irritable bowel syndrome (IBS). Findings are discussed concerning the role of protease-activated receptor-2 in enteric disease which may account for the presence of abdominal pain and diffuse symptoms in Blastocystis infection, even in the absence of fever and endoscopic findings. The availability of better diagnostic techniques and treatments for Blastocystis infection may be of value in understanding chronic gastrointestinal illness of unknown etiology.

Blastocystis sp. is the most common eukaryotic parasite in the intestinal tract of humans. Due to its strong impact in public health, in this study, we determined the frequency of different Blastocystis subtypes in patients in France. We hypothesized on the mode of transmission and tested a possible relationship between the subtype and symptomatic status. We obtained a total of 40 stool samples identified as positive for Blastocystis by microscopic examination of smears. Participants consisted of 25 symptomatic and 15 asymptomatic patients, for whom clinical and parasitological data were collected. For nested-polymerase chain reaction and genotyping, DNA was extracted directly from fecal samples or from fecal cultures. Morphological forms observed in fecal cultures were uncorrelated with symptomatic status. Genotyping using partial small subunit rRNA gene analysis identified a total of 43 Blastocystis isolates corresponding to 37 single infections and three mixed infections by two different subtypes. These 43 isolates belonged to five subtypes (1, 2, 3, 4, and 7) with predominance of subtype 3 (53.5%). Patient symptomatic status was uncorrelated with Blastocystis subtype.

Giriş: Blastocystis spp. neden olduğu klinik semptomlar nedeniyle günümüzde önem kazanan enterik bir protozoondur. Prevalansı dünyanın farklı bölgelerinde değişmekle birlikte gelişmekte olan ülkelerde daha sık görüldüğü bildirilmektedir. Bugüne kadar insanlarda 9 Blastocystis spp. alt tipi saptanmıştır ve bu lerin farklı klinik semptomlar ile ilişkili olabileceği öne sürülmüştür. Gereç Yöntem: Bu çalışmada formol-etil asetat yöntemi ile Blastocystis spp. varlığı saptanan 50 semptomatik hastadan elde edilen izolatlarının iki farklı besiyerinde kültürleri yapılmış, bu izolatların alt tip dağılımı sekanslama yöntemi ile belirlenmiş, alt tipler ile klinik bulgular arasındaki ilişkiler incelenmiştir. Bulgular: Örneklerden 40 (%80)'ı her iki besiyerinde de üremiş, 5 (%10)'i iki besiyerinde de ürememiş, 5 (%10) örnek ise iki besiyerinden sadece birinde üremiştir. 39 (%78) örnekte tek bir alt tip saptanırken, 11 (%22) örnekte birden fazla alt tip varlığı saptanmıştır. Örnekler arasında en sık ST3 saptanırken bunu sırasıyla ST1, ST5, ST2 ve ST4 takip etmiştir. Karın ağrısı 23 (%46) hastada olmak üzere en sık rastlanan klinik semptom olup, allerjik semptomlar ise 17 (%34) hastada gözlenmiştir. Bunun dışında hastalarda çeşitli gastrointestinal semptomlar ve eklem ağrısı varlığı da gözlenmiştir. Klinik semptomlar ile alt tipler arasında anlamlı bir ilişki saptanamamıştır. Sonuç: Çalışmamızda, gastrointestinal ve allerjik semptomları olan hastalarda ST3 alt tipi en sık saptanmıştır. Ayrıca her ne kadar az sayıda olgu bildirilmiş olsa da bir hastada eklem ağrısı saptanmış olması Blastocystis spp.'nin artrit ile ilişkisi olabileceğini ve klinisyenler tarafından göz önünde bulundurulması gerektiğini düşündürmektedir. Her ne kadar çalışmamızda klinik bulgular ile alt tipler arasında anlamlı bir ilişki bulunamamış olsa da Blastocystis spp. alt tiplerinin, klinik bulgularla ilişkilerinin anlaşılması için daha fazla araştırmaya ihtiyaç vardır. Anahtar Kelimeler: Blastocystis spp., alt tip, klinik belirtiler Introduction: Blastocystis spp. is an enteric protozoon that has grown in importance with recent knowledge of the symptoms, disorders it may cause. Its prevalence varies in different countries, but it is most frequently detected in developing countries. Nine subtypes (ST) of Blastocystis spp. have been detected in humans and it is suggested that these subtypes can be related to its varying clinical symptoms.

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

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.