Isolation and partial characterization of ΦSP-1, a Salmonella specific lytic phage from intestinal content of broiler chicken

Salmonella enterica subsp. enterica serovar Enteritidis is a major causative agent of gastroenteritis with contaminated eggs and chicken meat being the major source of infection. Phages are seriously being considered as a safe and cheaper alternative to antibiotics. The intestinal content of chicken was used as source for isolating phages. Phage designated as Phi SP-1 was selected for the study. Transmission electron microscopy (TEM) of phage Phi SP-1 revealed that it belonged to family Podoviridae. The optimal multiplicity of infection (MOI) was 5 phages/cell. Latent and rise period were calculated to be 30 and 55 minutes respectively, while burst size was 44 phages/bacterial cell. The genome size of Phi SP-1 was estimated to be 86kb from pulsed-field gel electrophoresis analysis (PFGE). The effect of different physical and chemical parameters like temperature, pH, salinity and CaCl2 were analyzed to optimize the conditions for large scale production of phages and to check the viability of Phi SP-1 under different physiochemical conditions. A temperature of 40 degrees C, pH 8 and 0.25M NaCl were found to be optimum for phage adsorption and it was able to survive up to a temperature of 50 degrees C for 3min. Capability to survive under hostile environmental conditions, absence of virulence genes in genome and genus specificity suggest suitability of Phi SP-1 to be used as a biocontrol agent.