Isolation of bacteriophages specific to Pseudomonas mosselii for controlling milk spoilage

Bacteriophages controlling heat-stable protease producing Pseudomonas mosselii were characterised and applied. Two Podoviridae family phages, designated ΦC106 and Φ21A, were isolated and shown to exhibit a broad host range. The optimal multiplicity of infection of both phages generating maximum titres was 10, latent periods were at 20 min and burst sizes were 1862 and 331 plaque-forming units per infected cell for ΦC106 and Φ21A, respectively. ΦC106 and Φ21A genomes did not encode known toxins, antibiotic-resistant genes, virulent factors of bacterial origin, or lysogenic markers such as integrase, recombinase, repressor/anti-repressor protein, and excisionase, guaranteeing their safety for addition into milk and dairy products. In vitro lytic activity and proteolytic activity of ΦC106 and Φ21A revealed a remarkable decrease in bacterial count and enzyme activity. These data suggest that ΦC106 and Φ21A are efficient in controlling the prevalence of spoilage-causing P. mosselii strains in dairy- and food-related environments.