الفهرس 
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Abstract
Blastocystis species are unicellular parasites that inhabit human GIT. Its pathogenic potential is still a debated issue due to the fact that it is the most frequently encountered parasite in healthy individuals as well as in patients with GIT symptoms. Several studies showed that Blastocystis infection can be associated with IBS, and the molecular studies demonstrated its extensive genetic diversity with at least 9 genotypes infecting humans. Thus, it was hypothesized that certain genotypes may possess clinically relevant differences. Therefore, the present study aimed to find out if certain Blastocystis genotypes have a relation with different clinical presentations in Blastocystis spp. infected individuals.
Three patient groups with different clinical presentation were included in the study; IBS, acutely GIT symptomatic and asymptomatic groups. Stool samples were collected from patients attending Suez Canal University Hospital, Ismailia, Egypt from the period of October, 2011 to May, 2012 and examined using wet mount and iodine staining with quantitative estimation of Blastocystis parasites (×400), FEAS and culture into Jones’ medium. Other protozoan infections were excluded by staining with Wheatley`s and acid fast trichrome stains. Salmonella-Shigella and Mac-Conkey agar were used to exclude common pathogenic bacteria. Only positive samples for Blastocystis without associated parasites or bacteria were included in the study. A total of 305 stool samples were examined to collect 57 positive cases of Blastocystis spp. infection with 19 cases in each group.
Subtyping using PCR with seven STS primers was done on isolates after in vitro propagation in Jones’ medium. Oral inoculation of culture forms (5×106) of a representing isolate for each of the detected subtypes, in each group of patients, were then used to evaluate the infectivity in experimentally infected rats followed by histopathological examination of their large intestine to evaluate pathogenicity of these subtypes.
This study showed the following results:
Diarrhea-predominant IBS (IBS-D) was the most frequent IBS clinical subtype detected among IBS patients with Blastocystis spp. infection.
Abdominal pain followed by diarrhea was the most frequently reported symptoms among patients of acutely GIT symptomatic group.
No correlation was found between parasite abundance and clinical presentation of different groups.
The amoeboid form was detected mainly in culture from most of the acutely GIT symptomatic group.
Three subtypes were detected among the study population (subtypes 1–3) with subtype 3 being the most predominant, followed by subtype 1. No significant difference was observed in the distribution of the detected subtypes among the study groups.
No statistically significant differences were observed between the detected Blastocystis subtypes and age, sex, residence, contact with specific animals or parasite abundance. No significant difference was found between Blastocystis subtypes detected in IBS group (subtypes 1 and 3) and IBS clinical subtypes.