الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Food-borne diseases are a gastrointestinal infection caused by foods containing harmful bacteria that caused by fecal contamination. Salmonella spp. are a most common cause of food-borne bacterial infections. This study aimed to detect Salmonella spp. in food product by phages. from 41 environmental and plant samples 22 bacterial isolates showed typical colonies on specific media XLD and Bismuth Sulphite agar. Tenisolates were confirmed as S. enterica using16S rRNA gene sequencing. Three highly lytic phages were detected against these strains. These phages named as Ø sal-1, Øsal-2 and Ø sal-3 Salmonella phages. They were isolated from the same samples collected to isolate Salmonella spp. Transmission electron microscopy revealed that, one of these phages (Øsal-1) has contractile tail and therefore belongs to the family Myoviridae, while the other two isolates (Ø sal-2 and Ø sal-3) had non-contractile tails, and therefore belong to the family Siphoviridae, these phages could infect S. enterica subsp. Enterica serotype. Typhimuriumbut couldn’t infect E.coli,Enterococcus and Enterobacter isolates .Phages were stable under different physical and chemical conditions. They endured high temperatures up to 72°C and pH ranged from 5 - 11, while they retained activity in NaCl solutions up to 3%. The phage Ø sal-3 was particularly interesting because it had higher rate and capacity of adsorption than the other two phages. Burst sizes were 124,121and 133 PFU and latent periods ranged from 45-50min observed for all isolate phages for phages Ø sal-1, Ø sal-2 and Ø sal-3 respectively.Result the total protein contentof the three phages were 0.21, 0.13 and 0.23 mg/ml, respectively. Results showed that DNA was intact and no digestion.The genomes of Salmonella phages were sequenced and it was found that, the size of Ø sal-1is 158,006bp with a G+C content of 50.4% and the genome is terminally redundant with 3.5Kb redundant regions and it has 247 ORFs. The genome size of Ø sal-2 is 42,391bp in length with a mean G+C content of 49.79%, and the genome contains 57 ORFs.The Ø sal-3 genomic sequence was 40,149bp in size with an overall G+C content of 51.3% and it contains 79 ORFs.
This study developed an application of bacteriophage as detection system for Salmonella, applied it to artificiallycontaminated fresh products by using phage amplification assay and were able to detect 10 CFU /g (1.0 log CFU/g)of S. Typhimurium after 24 h in fresh products. Whereas, the cultural enrichment method required 3 to 5days for detection. This method was effective for detection maybe valuable tool for assessment of the safety of food products with potential low cost compared to sophisticated rapid detection methods.