Evaluation of the potential of phage phSE-5 to fight Salmonella Typhimurium in milk, liquid whole egg, and eggshell

Aims This study aimed to evaluate the potential of phage phSE-5 to inactivate Salmonella enterica serovar Typhimurium in milk (at 4, 10, and 25 degrees C), liquid whole egg, and eggshell (at 25 degrees C for both matrices).Methods and results Since the success of phage treatment in food depends on maintaining phage viability towards different food conditions, firstly the stability of phage phSE-5 at different temperatures and pHs was assessed. The effect of phage phSE-5 against S. Typhimurium was then assessed in vitro (liquid culture medium-TSB) and finally in the selected food matrices. Phage phSE-5 was stable for long storage periods (56 days) at pH 7-8 and 4-25 degrees C. At 25 degrees C, the efficacy of phage phSE-5 was matrix-dependent with differences in the sample, relatively to the bacterial control, of 2.7, 4.6, 1.8, and 1.3 log colony-forming units (CFU) ml-1 in TSB, milk, liquid whole egg, and eggshell, respectively. Also, phage phSE-5 led to reductions relatively to the initial bacterial concentration only in TSB and milk with 1.9 and 2.1 log CFU ml-1 reduction, respectively. Additionally, this phage was more efficient at 25 degrees C in the tested matrices than at 10 degrees C (no reduction and 1.7 log CFU ml-1 reduction in TSB and milk, respectively; maximum difference of 1.7 and 3.3 log CFU ml-1 in TSB and milk, respectively) and 4 degrees C (no bacterial reduction/difference was observed in both TSB and milk). However, the decrease in temperature from 25 to 10 degrees C slowed down bacterial regrowth after phage treatment.Conclusions Our results show that phages are promising and environmentally friendly candidates for use as biocontrol agents against S. Typhimurium in milk, liquid whole egg, and eggshell, allowing a reduction in energy costs if carried out at 10 degrees C.