Characterization of phage-derived endolysin LysD6E against foodborne Escherichia coli

Foodborne Escherichia coli is one of the health-threatening pathogens existing on the surface of vegetables and fruits. Although antibiotics are the first line of defence against bacteria, increasing concerns are awake about the multidrug resistance caused by overuse and misuse of antibiotics. Therefore, alternative antibacterials are urgently necessary. In this context, we identified, cloned and expressed a novel endolysin LysD6E derived from marine phage D6E for its potential antibacterial action against E. coli . LysD6E consists of an Amidase_3 domain belonging to the N-acetylmuramoyl-L-alanine amidase family. LysD6E was stabile between 4 and 70 °C, and pH between 6 and 10. It had strong lysogenic activity against E. coli and Salmonella typhi . Furthermore, when applying 0.5 μM of LysD6E together with 5 mM EDTA on lettuce for 2 h, viable counts of E. coli ATCC 25922 reduced by 2.05 Log CFU/mL. Our findings suggest that phage-derived LysD6E has the potential against foodborne E. coli in raw vegetables.