Isolation and characterization of bacteriophages of Salmonella enterica serovar Pullorum

In this study, 2 bacteriophages of Salmonella Pullorum were isolated using an enrichment protocol and the double agar layer method. They were named PSPu-95 and PSPu-4-116, respectively, against clinical isolates of Salmonella Pullorum SPu-95 and SPu-116. The host ranges of the 2 bacteriophages were determined by performing spot tests with 20 bacteria strains. Both bacteriophages had wide host ranges. Bacteriophage PSPu-95 had a lytic effect on 17 of the 20 isolates (85%), and PSPu-4-116 produced a lytic effect on 14 isolates (70%) and was the only bacteriophage that produced a clear plaque on enterotoxigenic Escherichia coli K88. Transmission electron microscopy revealed the bacteriophages belonged to the order Caudovirales. Bacteriophage PSPu-95 was a member of the family Siphoviridae, but bacteriophage PSPu-4-116 belonged to the family Myoviridae. Both had a double-stranded DNA, which was digested with HindIII or EcoRI, that was estimated to be 58.3 kbp (PSPu-95) and 45.2 kbp (PSPu-4-116) by 1% agar electrophoresis. One-step growth kinetics showed that the latent periods were all less than 20 min, and the burst size was 77.5 pfu/cell for PSPu-95 and 86 pfu/cell for PSPu-4-116. The bacteriophages were able to survive in a pH range between 4 and 10, and they were able to survive in a treatment of 70°C for 60 min. The characterizations of these 2 bacteriophages were helpful in establishing a basis for adopting the most effective bacteriophage to control bacteria in the poultry industry.