الفهرس 
AIM OF THE WORKOnly 14 pages are availabe for public view
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Abstract
5-Summary
This study was conducted to isolate and identify E. coli from different sources during the period of September 2008 till October 2009 and characterize their ability to produce Enterotoxins and also the antibiogram of the isolates. A total of 384 samples were collected from different sources, Ismailia, Egypt 283 E. coli isolate were isolated and identified by cultural, biochemical, tests (IMVC) and Multiplex PCR technique for detection of stx1, stx2, eaeA, and EHEC hlyA gene which obtain only12 E. coli isolate.
The overall prevalence of E. coli was 100%. Among the isolates of E. coli, 31.43% isolates from human stool17.3%from raw water, 17.3% from animal stool, 16.5% from human urine, and 6.02% from processed meat product, 1.1% from poultry product 6.4% from sea food and 3.9% isolates from diary products. While the prevalence of E. coli positive for virulence genes were completely different based on the PCR assay. The antibiotic sensitivity pattern showed that the isolates were highly sensitive to Imipenem, Nitrofurantion, Gentamicin, Nitrofloxacin, Spectinomycin and Tetracycline and an increasing trend of resistance was recorded to Ampicillin, Vancomycin, Penicillin, Erythromycin and Rifampin. Serotyping was conducted only for the 12 E. coli isolate that positive for virulence genes. Only 10 strains with a percentage of 3.53% from the identified E. coli were found to be shiga toxin producer (owning Enterohemorrahgic characters).
198 isolates from total 284 with percentage of 70% were positive to Congo red indicator showing obvious invasive phenotype pattern on agar. While 75 isolates from total isolates with percentage of 26.6% were Enteroheamolysin producers causing clear blood lysis.
The present study investigated the PFGE profiles as the molecular typing technique for Shiga toxin producing Escherichia coli owning different genes and belonged to five different serogroups (O157, O158, O114, O124 and O26) isolated from different sources. 12 E. coli strains with characterized varied virulence genes (Stx1-Stx2- Eae hlyA) were subjected to finger printing by PFGE with Xba1 restriction enzyme to digest the genomic DNA. A total of 4 macrorestriction patterns were detected among the 12 virulent strains. PFGE types were recorded as I, II, III, and IV. Six strains were belonged to pattern I ,4 strains to pattern II while each of pattern III , IV were represented by one individual strain.
In a Pathogenicity test conducted for three weeks on Rats model challenged with Shiga toxin producing strains through intraperitoneal injection the result indicated marked damages, lesions and necrosis in the examined colon, kidney and liver and in the assayed animals. The Histologic investigations clearly reported that the degree of vascular damage and necrosis were greatly (related) dependant on the amounts of toxins produced by the pathogen.