الفهرس 
مقدمه الدراسهOnly 14 pages are availabe for public view
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Abstract
The objective of this study was to investigate intestinal bacteria in chickens because of the resulting increase in chicks mortality rate and reduction in hatchability and fertility. it was also intended to study the distribution of different enterobacteriaceae within orangs and of different sampled chikens. finally, the effectiveness of eleven antibiotics on these bacteria were tested and evaluated
During the last decade, a marked increase in focusing on the importance of meat and meat products has evolved (Ali, 1989). It has been anticipated that by the year 2020 the population of Egypt will have grown by 50 % and access to both global communications and commerce is raising the expectations of the population for more and better care and for new expensive health care technology (El-Henawy, 2000).
Such increase in population will undoubtedly be associated with an increase in consumption of meat as well as all other food products. It seems advisable to diversify the sources of animal protein, by encouraging the raising of breeds of farm animals that have a high potential in converting nutrients into animal protein and those animals suitable for our environment. Nowadays, poultry industry is considered one of the main sources of animal protein not only in Egypt put also all over the world due to efficiency cost of production and its short life cycle (Ali, 1989).
The production of poultry and poultry products has increased over the last several decades while the number of poultry producers has decreased (CAST, 1996). Total annual world poultry meat and egg production changed from 2.2 million operations producing 5.8 billion pounds of meat and 5.3 million dozen eggs yr-1 in 1960 to 91.000 operations producing 28.8 billion pounds of meat and 6.2 million dozen eggs yr-1 in 1990 (CAST, 1996; Marks and Knuffke, 1998).
Today in the U.S.A, 10 companies produce 92 % of the nation’s poultry. These companies are vertically integrated, meaning that they control all aspects of production, including hatcheries, feed mills, and processing plants (Marks and Knuffke, 1998). All of these statistics indicate that the poultry industry is consolidating into “factory farms”, or concentrated animal feeding operations (CAFO’s) with increased operation size and management intensiveness, CAFO’s are capable of producing more poultry from less input at a much lower cost to the consumer (Marks and Knuffke, 1998).
As poultry breeders continue to use population genetics in improving economically efficient stocks, undesirable correlated responses will occur. Selection for increased muscle may result in undesirable syndromes such as deep muscle myopathy (Siller et al., 1978; Grunder et al., 1984) and reduced immunological competence (Dunnington et al., 1987). These potential difficulties can be exacerbated when diets are formulated to maximize growth potential of these stocks (Katanbaf et al., 1989; Praharaj et al., 1996). A biological imbalance now expressed after generations of intense selection for rapidly growing, well-muscled broilers. It demonstrates a biological imbalance that is a consequence of allomorphic differences in heart and lung growth relative to the size of the animal (Dunnington et al., 1987).
In the United States, many food animals-poultry, swine and cattle are routinely treated with antibiotics in order to grow animals faster and to compensate for unsanitary conditions on many industrial farms (GAO, 2004). Recently, major increases in antibiotic-resistant bacterial infections in human populations have led to public health concerns regarding antibiotic use for such non-therapeutic purposes in animals destined for food production (GAO, 2004).
Organic and other non-conventional meat products are now available in developed countries to satisfy consumers’ demand for high-quality products that meet the following requirements: (i) guaranteed animal welfare during production; (ii) absence of chemical agents during animal feeding; (iii) environmentaly-friendly, and (iv) better taste than conventional products (Dransfield et al., 2005). However, little is known about the microbiological status of organic animal products and the potential microbiological risks linked to organic meat production. Currently, it is well known that several antibiotic-resistant bacteria isolated from humans originate primarily from animals raised for human consumption (Aarestrup, 2000; Sa´enz et al., 2001; Miranda et al., 2008).
1.2: Enterobacteriaceae:
The Gram-negative bacilli belonging to the Enterobacteriaceae are the most frequently encountered bacterial isolates recovered from clinical specimens (Winn et al., 2006). Widely dispersed in nature, these organisms are found in soil and water, on plants, and, as the family name indicates, within the intestinal tracts of humans and animals (Winn et al., 2006). Before the advent of antibiotics, chemotherapy and immunosuppressive measures, the infectious diseases caused by the Enterobacteriaceae were relatively well defined. Diarrhea and dysenteric syndromes accompanied by fever and septicemia, in classic case of typhoid fever, were known to be caused by Salmonella and Shigella species (Winn et al., 2006). Classic cases of pneumonia were known to be caused by Klebsiella pueumoniae, E. coli, Proteus species, along with various members of the Klebsiella and Enterobacter group (Winn et al., 2006). These bacteria were commonly recovered from traumatic wounds contaminated with soil or vegetative matter or from abdominal wound incisions following gastrointestinal surgery (Winn et al., 2006).