Isolation and Characterization of Lytic Pseudomonas fluorescens Bacteriophage isolated from milk

Phage-based biocontrol is an alternative method for preventing and controlling the occurrence of Pseudomonas spp. in food products. However, the use of bacteriophages to control heat-stable protease Pseudomonas fluorescens is still rare. The objectives of this study were to isolate lytic bacteriophages of P. fluorescens, and to evaluate their efficacy in controlling P. fluorescens at the laboratory level. Among these strains, only one phage, ΦTIS1, was isolated by using P. fluorescens TISTR 1887 as the host. Further analysis using electron microscopy indicated that ΦTIS1 belongs to the Myoviridae family. This phage ΦTIS1 was relatively stable at pH and temperature ranges of 4.0 to 12.0 and 4, 30, 37, and 45°C, respectively, after 1.5 h incubation. The partial ΦTIS1 genome was a linear double-stranded with a total length of 87,646 bp and a G + C content of 54.71%. In vitro studies of the effect of bacteriophages against P. fluorescens TISTR 1887 with phage ΦTIS1 using various multiplicity of infection (MOI) values showed a significant decrease in bacterial numbers during 6-12 hours of incubation, followed by bacterial regrowth. However, the phage was still able to significantly reduce the bacterial numbers compared to the control without phage. These findings suggest that phage ΦTIS1 has the potential to be an effective method for controlling the prevalence of spoilage-causing P. fluorescens strains in dairy industries.