Isolation and Characterization of a Novel Salmonella Phage vB_SalP_TR2

Abstract

Salmonella is a widely distributed foodborne pathogen. The use of Salmonella phages as biocontrol agents has recently gained significant interest. Because the Salmonella genus has high diversity, efforts are necessary to identify lytic Salmonella phages focusing on different serovars. Here, five Salmonella phages were isolated from soil samples, and vB_SalP_TR2 was selected as a novel phage with high lytic potential against the host Salmonella serovar Albany, as well as other tested serovars, including Corvallis, Newport, Kottbus, and Istanbul. Morphological analyses demonstrated that phage vB_SalP_TR2 belongs to the Podoviridae family, with an icosahedral head (62 ± 0.5 nm in diameter and 60 ± 1 nm in length) and a short tail (35 ± 1 nm in length). The latent period and burst size of phage vB_SalP_TR2 was 15 min and 211 PFU/cell, respectively. It contained a linear dsDNA of 71,453 bp, and G + C content was 40.64%. Among 96 putative open reading frames detected, only 35 gene products were found in database searches, with no virulence or antibiotic resistance genes being identified. As a biological control agent, phage vB_SalP_TR2 exhibited a high temperature and pH tolerance. In vitro, it lysed most S. Albany after 24 h at 37°C with multiplicities of infection of 0.0001, 0.001, 0.01, 0.1, 1, 10, and 100. In food matrices (milk and chicken meat), treatment with phage vB_SalP_TR2 also reduced the number of S. Albany compared with that in controls. These findings highlighted phage vB_SalP_TR2 as a potential antibacterial agent for the control of Salmonella in food samples.

Bacteriophages Isolated From Turkeys Infecting Diverse Salmonella Serovars

“…Heating could cause irreversible damage to phage particles, such as irreversible unfolding and dissociation of structural proteins, damage to the portal complex, disintegration of phage into head and tail, and leakage of DNA ( Ahmadi et al, 2017 ). Shang et al (2021) visualized the heat-treated phages with a transmission electron microscope. The detrimental effects of heat on phage structure were evidenced by phage tail aggregation, detachment of phage head and tail, and empty capsid.…”

“…It is expected that higher MOI and longer incubation time may be needed to achieve the same log reduction in cell concentration if using solid food matrices. Shang et al (2021) evaluated the ability of phage vB_SalP_TR2 to reduce Salmonella Albany contamination in pasteurized milk and chicken meat stored at 37°C for 6 h. They found that the phage was much more effective against S . Albany in pasteurized milk than in chicken meat ( Shang et al, 2021 ).…”

“… Shang et al (2021) evaluated the ability of phage vB_SalP_TR2 to reduce Salmonella Albany contamination in pasteurized milk and chicken meat stored at 37°C for 6 h. They found that the phage was much more effective against S . Albany in pasteurized milk than in chicken meat ( Shang et al, 2021 ).…”

A Cocktail of Three Virulent Phages Controls Multidrug-Resistant Salmonella Enteritidis Infection in Poultry

“…The filtrate (5 mL) was then mixed with 5 mL double-strength TSB pre-inoculated with 1% of overnight-cultured host strain and incubated at 37°C in a shaker at 160 rpm for 12 h. After the mixture had been centrifuged at 8000 rpm and filtered, phage presence was verified using the conventional double-layer agar method ( Van Twest and Kropinski, 2009 ; Guo et al, 2021 ). Double-layered agar plates were incubated at 37°C for 18 ± 2 h for visualization and single plaques on the plates were purified five times to obtain a pure phage isolate ( Duc et al, 2020 ; Shang et al, 2021 ). Phage propagation was performed as described previously ( Lu et al, 2020 ).…”

“…During the incubation period, 100 μL of the mixture was collected at 10 or 20 min intervals to calculate phage titer using the double-layer agar assay. Phage survival at different temperatures and pH values was assessed as described previously ( Shang et al, 2021 ). Briefly, phage suspensions (approximately 10 9 PFU/mL) were incubated at 30, 40, 50, 60, 70, or 80°C for 1 h to test thermal stability and at pH levels from 2 to 12 for 12 h to test pH stability.…”