الفهرس 
TitleOnly 14 pages are availabe for public view
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Abstract
prevalence up to 10% in developed countries rising to 50% in developing ones. It is a
highly polymorphic organism that takes different shapes during its life cycle. The
pathogenicity of this protozoan is still controversial with prevailing non-specific symptoms
as abdominal pain, nausea, vomiting, anorexia, weight loss, flatulence and acute or chronic
diarrhea. B. hominis is mainly transmitted by the fecal-oral route.
Diagnosis of B. hominis depends on different techniques such as direct microscopy
culture technique, immunoassay techniques and molecular analysis. Molecular
characterizations of Blastocystis have revealed extensive genetic diversity with 17 subtypes
(STs) being recognized based on SSU rRNA gene sequence.
Colorectal cancer is a major cause of morbidity and mortality throughout the world,
and the relation between B. hominis infection and CRC is not clear but infectious agents
such as bacteria, viruses and parasites may have an oncogenic potential. Recent studies
have suggested that B. hominis may possess the ability to induce the growth of colorectal
cancer cells. It is postulated that antigens isolated from B. hominis promote the
proliferation of cancer cells via the down-regulation of host immune cellular response
The aim of this study was to assess the possible association between B. hominis
infection and colorectal cancer
The current study was conducted on 100 participants recruited from the Oncology
Department of Alexandria Main Hospital, and were classified as group I which represents
CRC patients not receiving chemotherapy and group II represents patients on
chemotherapy treatment. In addition to 50 apparently healthy controls (group III) of
matching age and sex without a diagnosis of colorectal cancer and no history of cancer at
the time of the study
Stool samples were collected from all participants and were divided into two
portions. Part was used for microscopic stool examination and xenic culture and the other
part for DNA extraction and molecular analysis.
Among the examined participants, subjects aged from 25-<45 years represented the
highest prevalence of CRC (45%). With females having more participation than males
(62%).
Demographically in the current study the B.hominis infected patients aged from 25-
<45 years represented the highest prevalence (50%), However no statistical significant
difference was observed among the 40 B. hominis infected patients in the three studied
groups regarding neither age nor gender
Summary, Conclusion and Recommendations
57
Concerning the clinical manifestations in the present study there was no statistical
significant difference between three studied groups regarding symptoms including
abdominal pain nausea, vomiting and diarrhea.
Iodine wet mount revealed an overall parasitic infection rate of 34%. The frequencies
of parasitic infections in a decreasing order were: B. hominis; the most frequently detected
with infection rate (26.7%) of all cases 38%, 30% and 12% in groups I, II and III
respectively, followed by E. histolytica/E dispar. (4.7%), and G. lamblia (2%) while A.
lumbricoides (0.6%).
The culture examination of stool sample collected from the150 studied participants
revealed that the prevalence of B. hominis among them was 23% (n=35). .Sometimes it is
difficult to exclude the potential effects of other microbes during the culture technique
which inhibits the growth of organism.
In comparing the performance of microscopy and culture technique in the detection
of B.hominis among the 150 stool samples examined. It was noticed that direct wet mount
technique detected the highest percentage of positive cases (26.7%), followed by culturing
of stool samples which was positive for B. hominisin (23.3%) of cases.
Agreement analysis between microscopy and culture in the diagnosis of Blastocystis
was done by comparing the results of both techniques, the following was revealed: 33
samples out of the 150 examined cases were positive by both techniques (concordant
positive results). On the other hand, 108 cases were true negatives by both techniques
(concordant negative results). By analysis of the discordant results, 7 cases were positive
by microscopy were missed by culture, on the other hand, only 2 cases positive by
culture were negative by wet mount. A very good agreement between the two diagnosing
methods in the detection of B. hominis was observed
In the present study, the rate of B. hominis infection detected among CRC patients
group was 32% that was higher than recorded among healthy control group (12%), with a
statistical significant difference of B. hominis infection in groups (P=0.016). This finding
might support the association risk of the parasite with CRC
Out of 42 microscopically positive samples, B. hominis DNA was successfully
amplified by conventional PCR in 26 cases (60.5%),
In the current study PCR-RFLP analysis revealed that most of the obtained isolates
from suspected patients with gastrointestinal CRC belonged to group A (60%),group B
(24%) while group C (16%).
Further subtyping of obtained isolates was carried out using PCR-STS assay that
recorded the presence of five different subtypes (ST1, ST2, ST3, ST5 and ST7) among
investigated participants. The current study showed the predominance of ST1 (52%)
among targeted patients followed by ST3 (24%).
In the present study, There was no statistical significant difference between all
detected B. hominis subtypes in the three studied groups [ = 0.718)]
However, it is still debated whether distinct genotype(s) of human B. hominis
correlate with the pathogenic potential of this parasite
Summary, Conclusion and Recommendations
58
Conclusion
The present work studied the prevalence of B. hominis among colorectal cancer
patients and revealed:
There was no significant association between B.hominis infection and symptoms.
Significant statistical difference of B. hominis infection in CRC patients group as
compared to controls group which suggest possible association between B. hominis
and CRC, and postulate a potential risk of this parasite on carcinogenesis of Colon
and rectum.
A very good agreement between the two studied techniques (Direct wet mount smear
& culture) used in the present study.
PCR-RFLP analysis in present study classified B.hominis into three groups (A, B and
C) and revealed that the most of the obtained isolates from suspected patients with
CRC belonged to group A (60%) followed by group B (24%).
PCR-STS assay recorded the presence of five different subtypes (ST1, ST2, ST3,
ST5 and ST7) among investigated participants, and showed the predominance of ST1
(52%) among targeted patients.
Recommendations
Based on the findings of the present study, the following suggested items could be
recommended:
1. These findings need to be confirmed via further controlled epidemiologic
investigations to confirm the proposed association risk and to reveal other possible
risk factors that could contribute to the condition.
2. Further epidemiological studies needed to provide additional evidences for the
postulated role of zoonotic transmission of the disease to human population in
Egypt
3. Further study with more focus on chemotherapy and Blastocystis is therefore
suggested.