الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Summary
Bacteria are one of the most common causes of food poisoning. Unlike food spoilage bacteria, food poisoning bacteria do not affect the taste, smell or look of food. Food poisoning bacteria may cause problems in one of four main ways. They may transfer from raw to ready-to-eat foods due to poor handling and storage practices or may transfer onto foods from food handlers, pests or dirty equipment and utensils or may survive in food that is undercooked or may grow in food that is not stored at the correct temperature. E. coli, which are normal flora of the human and animal intestine, have been identified as a leading cause of food borne illness all over the world.
Most significant of this study is the fact that E. coli was isolated from “ready to eat” food. This result is even higher than that recorded for open market fresh meat which will still be processed before consumption.
The thesis was divided into two main sections:
The first section (Microbiological Analyses):
This section was focused mainly on the screening for the prevalence of E. coli isolates in food, Identification of the selected bacterial isolates, selection of the most related organisms that have the features of E. coli O157. The selected organisms were subjected to further morphological as well as physiological and biochemical identification. Also they were tested for the production of shiga toxin. All these steps could be summarized as the following:
Results of this section showed that, different bacterial isolates (100 in total) were found in Luncheon (31 isolates), Basturma (18 isolates), Salami (10 isolates), Fesikh (21 isolates) and Ringa (20 isolates). The Preliminary identification of the originated isolates was depended mainly on the selection of Gram negative isolates (the general feature of E. coli). Forty five Gram negative isolates were selected, 21 isolates were obtained from Luncheon, while 9 and 15 isolates were originated from Fesikh and Ringa respectively.
The bacterial isolates (45) were subjected for phenotypic identification. The identification was carried out to determine the morphological as well as the motility characters of the selected isolates. Results revealed that, 20 isolates (8 and 12 were isolated from Luncheon and Ringa respectively) were characterized as short rods and motile and selected as they showed some features of E. coli O157.
In a trial to identify the most likely isolates that may be suggested as E. coli 0157, 20 isolates (8 Isolates form Luncheon and 12 Isolates from Ringa) were allowed to grow on different selective (EMB, MAC and SMAC) media. The results showed that, only 2 isolates among the 20 bacterial isolates were suggested to be E. coli 0157, one isolate was obtained from Luncheon (L18) and one was from Ringa (R12). The suggested isolates were characterized by their abilities to ferment lactose (pink colonies) in MAC media and to exhibit the feature of green metallic sheen on EMB media while they were unable to ferment sorbitol (blue colonies). All these characters were promising to consider these isolates as E. coli 0157.
Confirmation tests for E. coli were applied using API 20E kit system which is a biochemical panel for identification and differentiation of members of the family Enterobacteriaceae. The most important feature that determines E. coli O157 is that its inability to ferment sorbitol which appeared obviously among the 2 bacterial isolates which suggesting that these isolates may be belongs to E. coli O157.
The two bacterial isolates which were previously identified by morphological, physiological and biochemical tests using API 20E system were subjected for further biochemical identification using automated Biomerieux Vitek-2 system. The 2 bacterial isolates showed inability to ferment sorbitol; on the other hand the L18 isolate was identified as β-Glucoronidase producer while the other isolate (R12) was unable to produce the same enzyme. This result strictly supports the suggestion of latter isolate (R12) to be identified as E. coli O157 strain.
Data obtained from the device revealed that, the identification of the tested isolates (R12 and L18) was classified as excellent identification (99% and 97 for R12 and L18 respectively) and indicated that the two isolates were identified as E. coli.
The bacterial isolates (R12 and L18) were allowed to grow on the production media (LB) and screened for their abilities to produce endotoxin using endpoint chromogenic limulus amebocyte lysate (LAL) QCL-1000 Reagents. The results (data not shown) revealed that, R12 isolate was able to produce endotoxin at concentration of 3457EU/ml while the toxin was not detected in the other isolate (L18).
Endotoxin from the isolate R12 was extracted, purified and identified by using of HPLC instrument. Shiga toxin standard (Stx 1 B subunit- SML0562 recombinant in E. coli, Sigma Aldrich Corporation, Saint Louis, USA) was used for the identification of the crude toxin extracted from the R12 isolate. Data obtained indicated that the R12 isolate was able to produce shiga toxin and the isolate was confirmed to be identified as shiga toxin producing E. coli (E. coli -O157/R12) strain.
The second section (Biological Analyses):
The results were focused on different items i.e. Food intake, body weight gain, feed efficiency ratio, biochemical analysis (liver and kidney functions) and histological examination.
Forty adult male albino (Sprague Dawley) rats weighing 175±25g were divided into 4 groups. Normal control (group I) were fed on standard diet only. The second group was considered as Positive Control (group II) where the rats were fed on standard diet for 4 weeks then intraperitoneally injected with 7mg/Kg (125 Units using Insulin syringe) of extracted shiga toxin for 24 hours. The third group (group III) was designed on rats which were fed on standard diet supplemented with fish oil for 4 weeks. At the end of incubation, the rats were intraperitoneally injected with 7mg/Kg (125 Units using Insulin syringe) of extracted shiga toxin for 24 hours. The last group (group IV) was designed on rats which were fed on standard diet supplemented with flax seed oil for 4 weeks. At the end of incubation, the rats were intraperitoneally injected with 7mg/Kg (125 Units using Insulin syringe) of extracted shiga toxin for 24 hours. The Positive control group was carried out at the same time with negative control and compared with other groups.
Feed intake, body weight gain, feed efficiency ratio were evaluated at the end of experiment. Results showed that there were no significant differences among groups may be due that the exposure time to the effect of the toxin was insufficient to cause an obvious change.
On the other hand determination of serum urea, creatinine, ALT, AST and Alkaline Phosphatase values revealed a statistically significant increase (p<0.05).
The histological examination of kidneys for both treated as well as control groups (group I, III and IV) showed no pathological appearance except for group II (positive control) which showed congestion of renal blood vessel and focal mononuclear inflammatory cells infiltration.
In the quantitative evaluation of liver histological changes, vacuolization, hydropic degeneration as well as slight activation of Kupffer cells of hepatocytes were observed in Stx treated rats (group II). While the histological examinations of livers for both treated as well as control groups (group I, III and IV) showed no pathological appearance.
Finally, it is concluded that Escherichia coli is still a major concern in the food industry and research, such as the research performed in this thesis, is necessary for helping researchers, food industry employees, and consumers become aware of the issues surrounding foodborne disease and what is being done to help control outbreaks in the future. We must continue to learn about and perform research on E. coli O157 and other foodborne pathogens so that we might drive the food industry, and potentially policy, in the right direction for reducing the risk of foodborne disease and making food safer for everyone to enjoy. At The end of experiment Fish oil was found to be more efficient in improving the liver as well as kidney functions than flaxseed oil