الفهرس 
Review of LiteratureOnly 14 pages are availabe for public view
Abstract
6. English Summary
The antibiotic resistance crisis is represented as one of the major health threats in world. The misuse of antibiotics in animal and agriculture over several years has been affected in the development of drug resistance in many foodborne pathogens that cause many animal and human infections.
Recently, many researchers have been looking at the utilization of phage as prospective strategy to overcome the multidrug resistant bacteria that cause infections in poultry. Bacteriophages are viruses that specifically infect and lyse their hosts. Most of phages are safe, because they are very specific to their bacterial hosts. Therefore, it would fruitful to utilize them to prevent many bacterial diseases.
Thus, the aim of this study was to investigate the occurrence of antibiotic resistance pathogenic bacteria isolated from broiler chickens and use their phages as an alternative means to combat these multidrug resistant pathogens.
The results summarized in the following:-
1. Different food borne pathogens were isolated and identified in the samples collected from infected broiler chicken farms in Sharkia samples. These foodborne pathogens were Salmonella spp., E.coli, Proteus spp., S.aureus and B.cereus.
2. The results showed that the most prevalent Salmonella serovars were S. Typhimurium (7.5%), S. Enteritidis (5.0%), and S. Kentucky (3.0%). The prevalence of E. coli in collected samples was (4.5 %), For Proteus spp. the percent of their prevalence was 7.5 %. Other bacterial pathogens were present in low numbers.
S. aureus represents 4% and B. cereus percentage was 1.5% from collected samples.
3. All pathogenic bacterial strains were tested for their sensitivity to different antibiotics. The results indicated that these bacteria were resistant to at least 3 tested antibiotics confirmed that these strains were multidrug resistant strains.
4. Antibiotic resistance genes were detected on resistant isolates, the screened genes was VIM, blaTEMand IMP; PCR results indicated that all tested pathogenic isolates contained antimicrobial resistance gene (blaTEM, which are known to exhibit the resistance. B. cereus showed only the presence of IMP and VIM resistant genes, while mecA gene was found in methicillin resistant S. aureus (MRSA) isolates.
5. Six bacteriophages of different plaques morphology and size targeting these multidrug resistant bacteria have been isolated and characterized from different sewages samples in 10th Ramadan city, Egypt.
6. The isolated phages showed variations in their capabilities to infect and lysate the target pathogen. Six phages were selected for characterization-included phages active against Salmonella serovars (Salmacey1, Salmacey2, and Salmacey3), Proteus (Protmacey), S. aureus (Staphmacey), and Bacillus (Bacmacey).
7. The electron microscopy of the six selected phages revealed that they related to Myoviridae, Podoviridae, Siphoviridae families. Two Salmonella phages (Salmacey1, Salmacey2) and Bacmacey phage were morphologically characterized and relate to the family Siphoviridae, while, Salmacey3 and Staphmacey were belonging to the family myoviridae. Protmacey appeared to be a member of the family Podoviridae morphotype C3 based on their structure in electron micrograph.
8. All isolated phages had different host range against tested bacteria, Salmonella bacteriophages had lytic effect on four Salmonella serovars, S. Typhimurium, S. Enteritidis, S. Kentucky and S. Typhi and one strain of Citrobacter freundii.Moreover, only (Salmacey1, Salmacey2) had a lytic effect on Enterobacter cloacae and Salmacey3 was able to infect E.coli suggesting that these bacteriophages are polyvalent. While the others phages (Protmacey, Staphmacey, and Bacmacey), were active against their hosts only indicated that these phages had a narrow host range.
9. The growth kinetics of the isolated phages was determined and the results of burst sizes and latent periods were determined for all phages with burst size varied between 80 and 120 pfu per infected cell with latent period 30-60 min respectively.
10. All the isolated phages were stable, between temperature ranges of 30–70°C. The viability of isolated bacteriophages was significantly decreased with increasing the temperature until completely disappeared at certain temperature degree called thermal inactivation point, which was ranged between (60-80ºC). All isolated phages were active at room temperature, with no significant loss in phage titers, which is a very important factor for therapeutic application.
11. The viability of phages was rapidly decreased toward acidity compared to pH7. The optimum pH value for the phages stability was at pH 7, all phages completely inactivated at pH 2 and pH10.
12. The genomic DNA from each phage was isolated and digested with different restriction enzymes. The results of the digestion patterns of genomic DNA with different restriction endonuclease showed different banding patterns for the phage DNA, indicated that genomic materials of the isolated phages was represented as dsDNA.
13. The lytic activity of the isolated phages was also evaluated in vitro to confirm their potential as biocontrol agents. Phages (Salmacey1, Salmacey2, and Salmacey3) were able to lyse the growth of S. Kentucky compared with that seen in untreated control at 37°C. Furthermore, Phages (Protmacey, Staphmacey, and Bacmacey) were able to reduce the growth of their hosts (Proteus, S.aureus and B. cereus respectively. The results demonstrated a quick reduction of bacterial cells after treatment with theses phages.
14. About future study, a priority objective of our future research will be to identify the nucleotide sequence and protein of the isolated phages and the use of phage mixtures to cover a wider inhibitory spectrum and to avoid, at least to some extent, the development of resistance. In summary, this study provides polyvalent lytic bacteriophages that can be employed to treat the multi-drug resistance pathgogenic bacteria isolates in broiler chickens in different regions of Egypt for which there are no longer any efficient treatments available.