Biological and genomic characterization of a polyvalent phage PSH-1 against multidrug- resistant Salmonella

Background Bacteriophage has been renewed attention as a new antibacterial agent due to the limitations of antibiotic treatment. Through the biological characterization and genome analysis of the isolated Salmonella phage, the bacteria can be specifically killed through the advantages of safe, efficient and fast bacteriophages in the future, so as to reduce or even solve the current drug resistance and safety problems of Salmonella bacteria. Results In this study, a virulent lytic bacteriophage (named Salmonella phage PSH-1) of Salmonella was isolated from the sewage samples of a large-scale pig farm, it can not only lyse multidrug-resistant Salmonella but also E. coli , and then its biological characteristics, genome and bacteriostatic ability were investigated. The results showed that the initial titer of PSH-1 was 1.15x10 ¹⁰ PFU/mL and the optimal multiplicity of infection (MOI) was 0.01, PSH-1 has stable activity in the range of pH 3.0–11.0. One-step growth curve showed that its latent period was 20 min, burst time was 80 min, and the burst was 495 particles. The whole-genome sequencing results revealed phage PSH-1 had a linear dsDNA with 48466 bp length. The G/C content was 45.33%. Non-coding RNA genes and virulence factors were not found. Eighty- five open reading frames (ORFs) were identified after online annotation. By tests, the use of phage could succeed in controlling the artificial salmonella contamination in milk at a range of temperatures. Conclusions This study reports a novel Salmonella phage PSH-1, which has a robust lytic ability, no virulence factors, and good stability. The characterization and genomic analysis of PSH-1 will develop our understanding of phage biology and diversity and provide a potential arsenal for controlling of salmonellosis.