Control of Salmonella Enteritidis on ready-to-eat fresh produce using a lytic bacteriophage

Bacteriophages can prevent the spread of foodborne pathogens. Salmonella is a foodborne pathogen posing a global public health risk, evidenced by frequent outbreaks due to ready-to-eat (RTE) produce consumption. Using tomato as a model crop, this study aimed to isolate and characterize a lytic bacteriophage against Salmonella Enteritidis (ATCC13076) (SE), one of the major serovars linked to salmonellosis in Sub-Saharan Africa.

Salmonella phage SCF was isolated from chicken feces using Salmonella Enteritidis as a host. Based on its icosahedral capsid and long, thin tail detected by transmission electron microscopy, the phage was assigned to the class Caudoviricetes. Its genome has 108.56 kb, a G+C% of 39.02, and is closely related to Salmonella phage SE11 (Genbank: NC048786). Virulence or lysogenic genes were not detected. It lysed Salmonella Typhimurium (ATCC14028) but not other γ-Proteobacteria (e.g., E. coli, S. marcescens, E. cloacae, P. aeruginosa, K. pneumoniae). The one-step growth curve revealed a burst size of around 72 virus particles/host cell and a latency time of ~20 minutes. The phage SCF was stable between 8˚C-50˚C and pH 4-8. Phage SCF prevented biofilm formation and significantly decreased existing 72 h biofilms generated by SE. It was used successfully to control SE on the tomato surface. A 2-hour treatment of SE-contaminated tomatoes with phage SCF at ambient temperature reduced SE counts by up to 5.3 log₁₀ units.

These findings demonstrate that Salmonella phage SCF could be employed as a biocontrol agent to tackle SE and improve the safety of RTE produce such as tomatoes.