Isolation and Characterization of Salmonella Typhimurium Lytic Bacteriophages from Fermented Shrimp Paste (Terasi)

Fermented shrimp paste (terasi) is one of Indonesian naturally fermented products, and mainly still produced traditionally. The traditional terasi is a high potential to be contaminated by pathogenic bacteria such as Salmonella. Lytic bacteriophage can be used to control Salmonella in the terasi, before the product is accessible for consumption. This study was aimed to isolate lytic bacteriophage specific for Salmonella Typhimurium, and characterize the lytic bacteriophages towards a range of temperatures, pH, and salinity. Lytic bacteriophages were isolated from terasi products (modern and traditional made), poultry litter, and river water using the double-layer agar method. Salmonella Typhimurium was used as the main host since this species was found in traditional terasi. The determination of the host-range of lytic bacteriophages against other pathogenic bacteria was carried out by the spot test method, and then the lytic bacteriophages were characterized towards variation of temperatures (30 °C, 40 °C, 60 °C, 70 °C, 80 °C), pH (2, 4, 8, 10, 12), and salinity (0.1 g/mL, 0.15 g/mL, 0.2 g/mL, 0.25 g/mL). The bacteriophages exhibiting lytic activities against Salmonella Typhimurium were found in traditional terasi, poultry litter, and river water. However, they could not lyse the other tested bacteria. These lytic phages demonstrated relatively similar degrees of resistant to a range of temperature (30-70°C), pH (4-10), and salinity (0.1 g/mL – 0.2 g/mL). These results indicate that traditional terasi is a potential lytic bacteriophage reservoir, and future work is required to formulate cocktail bacteriophages incorporated into the traditional terasi to improve the product safety and quality.