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 ΦSP-1 was selected for the study. Transmission electron microscopy (TEM) of phage ΦSP-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 ΦSP-1 was estimated to be 86 kb 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 ΦSP-1 under different physiochemical conditions. A temperature of 40 °C, pH 8 and 0.25 M NaCl were found to be optimum for phage adsorption and it was able to survive up to a temperature of 50 °C for 3 min. Capability to survive under hostile environmental conditions, absence of virulence genes in genome and genus specificity suggest suitability of ΦSP-1 to be used as a biocontrol agent.