الفهرس 
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Abstract
Food-borne diseases are a persistent challenge to the public health worldwide. New and emerging pathogens appears, and new food vehicles continue to be implicated as a result of the changing industrial ecology of food production and consumption. Recent outbreaks of food-borne disease associated with fresh products have raised concern that these food may be an increasing source of food-borne infections. Fresh and minimally processed fresh (MPF) fruits and vegetables are good media for growth of microorganism. They have been involved in outbreaks because of the consumption of products contaminated by pathogens. They are also sensitive to various spoilage microorganisms such as pectinolytic bacteria, saprophytic Gram-negative bacteria, lactic acid bacteria, and yeast. Contamination of these products occurs at every stage of the food chain, from cultivation to consumption. Polluted environments during cultivation or poor hygienic conditions in processing increase the risk of contamination with food-borne pathogens. This study aimed to assess the microbiological quality of some fruits in different districts in Alexandria and search for possible organisms causing food-borne disease such as Salmonellae, and Shigellae. The study was performed on 150 fruit samples (50 strawberry, 50 cantaloupe, 25 date and 25 fig) as well as 50 MPF fruits (fruit salad) collected from different sources and localities in Alexandria (Misr Station, Ramleh Station, El-Manshia, Boulkley, Smouha, El-Hadara, Sidi Gaber, El-Saa, Asafra, El-Ibrahimia, Roushdy and Cleopatra) in the period from spring to summer 1998. Twenty five grams of each sample were weighted under aseptic condition, transferred to a stomacher bag with 225 ml buffered peptone water and mixed thoroughly in a stomacher for 2 minutes. Then each food sample was subjected to: 1- Total aerobic plate count determination: On plate count agar after transferring 1 ml from food homogenate to 9 ml of peptone water to obtain 3 dilutions for each sample. Appropriate amount of melted plate count agar were transferred into two sterile dry Petri-plate containing a proper amount of each dilution. The plates were incubated at 37°C for 3 days. The plates were counted with the aid of Quebec counter, and the total aerobic bacterial count per gram of the tested sample was calculated. 2- Total coliform most probable number (MPN) determination: Presumptive test was preformed by pipetting aseptically 1 ml of each of the prepared dilutions of food into each of three tubes of LSTB. Tubes were incubated at 35°C and examined after 24 and 48 h. Positive tubes – as denoted by gas formation were confirmed by subculturing a loopful from each tube into a tube of brilliant green lactose bile broth. These were incubated at 35°C for 48 h and positive tubes showing gas production were recorded. The total coliform counts were estimated and reported as the most probable number present in 1 g of the original sample using the MPN table. 3- E.coli MPN determination; The positive presumptive LST tubes were subcultured into EC broth tubes and incubated at 45.5°C for 48 hours. Each gas positive EC tube were subcultured onto L-EMB agar plate and all plates were incubated at 37°C for 24 hours. The suspected E.coli colonies were subjected to Gram-stain and biochemical identification (Indol, Methyl red etc). MPN of E.coli per g were computed according to Gram stain and biochemical tests. 4- Salmonella and Shigella determination: a- Pre-enrichment. The previous fruit homogenate bottle was incubated at 37°C for 24 hours. b- Enrichment; from each pre-enrichment bottle 10 ml were transferred to each of 100 ml Tetrathionate broth and 100 ml Selenite cystine broth for isolation of Salmonella and 100 ml GN broth and another 100 ml Selenite cystine broth for isolation of Shigella. The formal bottles were incubated at 42°C and the later at 37°C for 48 hours. Three- Plating out. A loopful from each Salmonella enrichment bottle was subcultured on BG and XLD agar and from each Shigella enrichment bottle was subcultured on MacConkey, XLD, and DCA agar plate. All plates were incubated at 37°C for 24 hours. All suspected colonies of Salmonella and Shigella were identified by biochemical and serological tests. The results of this study showed that: 1- The total aerobic bacterial count among different types of fresh fruits were ranging from 102 to 107 cfu/g. 2- The mean total coliform MPN among different types of fresh fruit samples were ranging from 2.2x101 to 2.2x103 coliform/g.