الفهرس 
Introduction and aim of workOnly 14 pages are availabe for public view
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Abstract
A total of 400 food samples including 200 meat (luncheon, frozen lean beef, raw lean beef and frozen chicken meat) and 200 dairy products (white cheese, kareesh cheese, turkey cheese and pasteurized milk) were examined for Salmonella prevalence. Salmonella could be detected in 14 (28%), 4 (8%), 11 (22%) and 7 (14%) of luncheon, frozen lean beef, raw lean beef and frozen chicken meat samples, respectively. The results of antibiotics susceptibility profiles highlighted the presence of multi-drug resistance by several serovars of Salmonella, especially S. Typhimurium. Regarding the formation of the biofilm, the obtained results showed that the serovars were differed in their ability to form it where S. Typhimurium was the strongest producing serovars with 10 isolates (10/35; 28.57%), followed by S. Enteritidis were 3 isolates (3/16; 18.75%). The presence of Salmonella in Egyptian foods it raises the alarm that control over food quality and safety must be tightened. New and natural antimicrobials as an alternative control system are now an urgent need to overcome stubborn bacterial infections. Salmonella Typhimurium has become the most frequent serovar responsible for salmonellosis in humans around the world. The high antimicrobial resistance and biofilm production make this pathogen more dangerous. We aimed to isolate a broad lytic phage to prevent Salmonella infection and reduce its biofilms. Using S. Typhimurium (ST-4) as a host, seven phages were isolated, and only three phages showed clear lytic plaques, two members of the Siphoviridae family (vB_STM-1 and vB_STM-3) and one of the Myoviridae family (vB_STM-2). The vB_STM-2 phage was the most potent broad lytic phage, infecting 100% of tested S. Typhimurium serovars and non-Salmonella strains. Eventually, the vB_STM-2 phage showed significant (p < 0.05) efficacy in the elimination of S. Typhimurium (ST-4) from contaminated chicken breasts at both storage periods with high titer stability. The Salmonella count showed a severe decline from 7.00 ± 0.63 log10 CFU/cm2 to 0.88 ± 0.17 log10 CFU/cm2 on the seventh day of the short-term storage, and from 5.13 ± 0.44 log10 CFU/cm2 to 1.10 ± 0.12 log10 CFU/cm2 on day 27 of the long-term assay. In both periods, the phage titers remained stable, with insignificant (p < 0.05) loss. Therefore, this phage is considered a prime candidate to combat multi-drug-resistant S. Typhimurium and its biofilms.