ISOLATION AND INITIAL CHARACTERIZATION OF A Myoviridae PHAGE FOR CONTROLLING ZOONOTIC Salmonella Typhimurium AND Salmonella Enteritidis FROM BROILERS IN EGYPT

This study targeted isolation and characterization of phage against multidrug resistant (MDR) Salmonella Typhimurium and Salmonella Enteritidis recovered from broilers and to evaluate the lytic effect of the phage on growth of Salmonella serovars. Salmonella isolates were recovered from caecal contents, liver and breast meat of broiler chickens from retail outlets at Sharkia Governorate, Egypt. Salmonella Typhimurium (n=14) and S. Enteritidis (n=11) were tested for their antimicrobial susceptibilities against 15 antimicrobials by disc diffusion method. Isolates of S . Typhimutium and S. Enteritidis were 100% resistant to seven antimicrobial agents. The phage was isolated from Zagazig sewage water by spot test and double over layer agar assay. The phage designated as phiSalmchick1showed an icosahedral head and contractile tail structure in electron microscopy, indicating a member of the family Myoviridae . The phage was a polyvalent infecting a wide host range of all MDR strains of S . Typhimurium, S . Enteritidis, S . Paratyphi, E. coli serotypes O26 and O168 and Klebsiella pneumoniae. Myovirus phage had burst size of 100 plague forming unit (PFU)/cell with latent period of 60 min. The phage genome had double-stranded DNA by molecular analysis. The lytic effect of phiSalmchick1 phage was in vitro assessed on growth of S . Typhimurium and S . Enteritidis isolates by measuring the optical density (OD) of the liquid media during Salmonella growth at 37 °C and the multiplicity of infection (MOI) was equal to 1.0. Significant reductions were observed in OD of S . Typhimurium and S . Enteritidis treated with the phage after 24 hrs incubation compared to the controls (P<0.05). The myovirus has a high potential for phage application to control zoonotic and MDR Salmonella serovars isolated from broiler chickens in Egypt. Key words: multidrug resistant; Salmonella serovars; Myoviridae phage; broiler chickens; in vitro control