الفهرس 
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Abstract
Blastocystis is the most common intestinal parasite worldwide and has been gaining much attention from parasitologists. Individuals infected with Blastocystis are susceptible to dehydration, weight loss, flatulence and acute or chronic diarrhea, yet, many infections go undetected.
Methods such as microscopy, cultivation techniques, immunoassay methods, and molecular analysis are used in the diagnosis of B. hominis. Blastocystis spp. was reported to include at least 17 separate subtypes (STs) that were initially proposed among mammalian and avian isolates (ST1 to ST17) with varying frequency in host species. Recently, 15 new STs (ST18–ST32) were discovered in birds. Four of these additional STs (ST18-ST20 and ST22) are not yet regarded as valid because they are probable chimaeras emerging during PCR amplification. Hence, this study was designed to identify and compare the genetic subtypes of Blastocystis among primary schoolchildren in El-Beheira and Kafr El Sheikh governorates, Egypt.
To fulfill this aim, stool samples were collected from 150 school children residing in rural areas in Kafr El-Sheikh and El Beheira governorates (75 children from each) their ages ranged between (6-12) years. The collected stool samples were examined microscopically after FEACT and were cultivated in Jones’ medium supplemented with 10% human plasma for 72 hrs. PCR assay was performed on all microscopy and/or culture Blastocystis positive samples (single or combined). Sequencing was performed on 10 random PCR Blastocystis positives samples for further grouping and subtyping.
In the present study, stool results revealed an overall parasitic infection rate of 56.0% and 32.0% by FEACT, in which Blastocystis amounted to 34.7% (26/75) and26.7% (20/75) in Kafr El Sheikh and El Beheira respectively. However, cultivation on Jones’ medium generated better results than microscopy in the detection of Blastocystis with infection rates of 40.0 %and30.7%in the two governorates correspondingly.
To compare the outcomes of microscopy and culture, an agreement analysis between the two methods was conducted. Microscopy and culture shared the detection of 46 positive cases as well as 97 negative ones pointing to a very good agreement between both techniques. However, culture revealed seven samples not detected by microscopic examination, these seven missed cases are most probably due to erratic shedding.
In the current study, the 53 Blastocystis positive samples were subjected to a confirmatory conventional PCR analysis which resulted in 40 positives; 25 (83.3%)from Kafr El-Sheikh and 18(78.3%) from El Beheira, results were statistically significant.
In the two different governorates: In Kafr El Sheikh B. hominis (ST3) (two samples) were found to be the most common, followed by ST1, ST2, one sample for each. In El Beheira children (ST3) (three samples) were found to be the most common, followed by ST10 (one sample); this is the first occurrence of ST10 in humans in Egypt. It is possible that differences in exposure to environmental and/or animal infection sources account for the documented heterogeneity in frequency of the four major STs among Egyptian regions or
even within the same country. This variation was also described in the area of Kafr El-Sheikh and El Beheira, which is where the current survey was conducted. The10 sequenced samples were submitted in BLAST. Eight isolates were identified with ST3 representing 62.5% of the detected isolates. In Kafr El-Sheikh, subtypes ST1, ST2 and ST3 were detected (ST1 and 2 in males only, ST3 one in each gender). In Al Beheira children ST3 and ST10 were detected (ST3 in one male and two females but ST10 were detected in one male).
Conclusively, ST3 was the most commonly detected ST (5 and 2 isolates in Kafr El Sheikh and El Beheira governorates respectively), in addition to ST1 and ST2 (one isolate each) in Kafr El-Sheikh only. A single isolate in El Beheira was identified as ST10, it is the first and exclusive occurrence of ST10 among humans in Egypt. This implies a possible concurrent exposure of the villagers to different sources of infection or few sources containing several genotypes.