The application of adaptively evolved thermostable bacteriophage?YMFM0293 to control Salmonella spp. in poultry skin

Bacteriophages, bacterial viruses, are now being re-highlighted as one of the promising alternative antimicrobial agents to control bacterial pathogens in various fields, including the food industry. However, wild-type (WT) phages isolated from nature are vulnerable to external stresses such as heat, limiting the usability of phages in thermal processing. Here, we applied an adaptive laboratory evolution approach to improving the heat stability of newly isolated Salmonella-infecting lytic phage phi YMFM0293 and examined its application in the poultry scalding process. After 15 cycles of exposure to sub-lethal temperature, the obtained adaptively evolved (AE) phages maintained approximately 3-log more infectious particles at 73 or 74 degrees C than the WT and non-heat -treated control phages. Missense mutations mainly concentrated in the genes related to the phage tail module were identified from the independently obtained heat-challenged phages, regardless of host Salmonella's heat -shock protein chaperone induction. These results demonstrated the necessity and sufficiency of the phage ex-posures to heat for thermal adaptation and suggested the involvement of the phage tail in heat stability. No significant physiological or morphological changes except the mutually offsetting phage replication parameters were observed in the AE phages. Accordingly, hot water supplemented with the AE phages significantly reduced the number of artificially contaminated Salmonella cells on chicken and duck skin in the mimicked scalding process. The AE strategy used here could be applied to other WT phages to improve their usability as more feasible antimicrobials for food safety.

Automated summary

Bacteriophages are being reconsidered as a potential alternative to control bacterial pathogens in the food industry. By implementing an adaptive laboratory evolution approach, the heat stability of a newly isolated Salmonella-infecting phage was improved and demonstrated its efficacy in the poultry scalding process.