Application of phage cocktail for control of shiga toxin-producing Escherichia coli in foods and food contact surfaces

Abstract

Background: Shiga toxin-producing Escherichia coli; STEC remains a global public health and food safety challenge. Despite the various control measures available, there are still reports of outbreak and illness caused by this pathogen. Therefore, it is important to reduce this pathogen along the food chain. Methods and materials: In this study, seven STEC phages were isolated from irrigation ponds and streams. The host range and lytic activity of phages were characterized using 120 STEC strains previously isolated from foods. CFM1, WWM1 and WWM6 showed a wide host range and broad lytic activity. A phage cocktail designated CCD1 containing the three lytic phages for STEC was tested for its ability to reduce contamination of hard surfaces (gypsum board), fresh vegetables (lettuce, cabbage, cucumber and carrot). The samples were experimentally contaminated using a mixture of five STEC strains and were treated with CCD1 (test sample) and sterile SM buffer (control samples) at 4 °C and 25 °C. Results: After 10 minutes of treatment with the CCD1 cocktail using different phage concentration (1010, 109, and 108 PFU/ml), statistically significant reductions (P = < 0.05) of 99.50%, 97%, and 95%, respectively were observed in the number of viable STEC recovered from the gypsum board surface. Also, reduction was observed in the fresh vegetables samples ranging from 95% (at 30 mins) to 99.99% (at 12 hours). Conclusion: Findings from this study suggest that phages can be used to decontaminate vegetables and food contact surfaces. Its application as biocontrol could be useful in the prevention of food borne illnesses and outbreaks.