Characterization of a novel Siphoviridae Salmonella bacteriophage T156 and its microencapsulation application in food matrix.

Salmonella is one of the most common causes of foodborne diseases and can cause severe economic loss. Increased antibiotic resistance, particularly of multidrug-resistant strains, has led to the use of phages as substitute agents. However, bacteriophages are usually sensitive to harsh environments. At present, microencapsulation is one of the methods to solve this problem. But there are few studies on the application of microencapsulated bacteriophages in food matrix. In this study, a novel Salmonella phage T156 was firstly studied for its biological characteristics. T156 belongs to the T5-like Siphoviridae family, with broad host spectrum and potent lytic ability against tested Salmonella strains, including multiple antibiotic-resistant Salmonella. It also showed valuable characteristics such as high pH (3.0-12.0), thermal tolerances (30-50 °C) and a short latent period (10 min). Genome analysis indicated T156 genome comprised a 123,849 bp DNA with 176 putative open reading frames, of which 56 ORFs were annotated to known functions. No genes associated with antibiotic resistance, virulence factor and lysogeny were found in T156 genome. Then, orifice-coagulation bath method was used to microencapsulate bacteriophage T156. Microencapsulated bacteriophage can effectively inhibit the growth of Salmonella in artificially contaminated milk and lettuce at 4 °C and 25 °C. At 25 °C, the maximum antibacterial efficacy of phage in milk and lettuce were 57.93% and 55.47%, respectively. This is the first report about microencapsulated bacteriophage infecting Salmonella in food matrix. It can provide insights into fundamental researches on microencapsulated bacteriophage for future utilization in food.