Characterization of a novel endolysin LysSA11 and its utility as a potent biocontrol agent against Staphylococcus aureus on food and utensils

- LysSA11 endolysin is derived from the Staphylococcus aureus virulent phage SA11.
- LysSA11 is comprised of an CHAP domain and a novel cell wall binding domain.
- It rapidly killed MRSA in milk or on ham both at refrigeration and room temperature.
- LysSA11 endolysin also worked efficiently on utensils as a sanitizer.

Here we show that the LysSA11 endolysin, derived from the virulent Staphylococcus aureus phage SA11, has lytic activity against staphylococcal strains. Bioinformatics analysis revealed an enzymatically active CHAP (cysteine, histidine-dependent amidohydrolases/peptidases) domain at the N-terminus of LysSA11 that showed amidase activity. A novel cell wall binding domain (CBD) in the C-terminus could bind to a broad spectrum of staphylococcal cells. The bactericidal activity of LysSA11 was determined in food and utensils artificially contaminated with methicillin-resistant S. aureus (MRSA). The amounts of MRSA bacteria in milk and on ham were significantly reduced by 1.44-log CFU/mL and 3.12-log CFU/cm3, respectively, within 15 min at refrigeration temperature (4 °C) and by 2.02-log CFU/mL and 3.37-log CFU/cm2, respectively, within 15 min at room temperature (25 °C). Moreover, a polypropylene plastic cutting board and a stainless steel knife artificially contaminated with approximately 4-log CFU/cm2 of MRSA also showed complete bacterial elimination after a 30-min treatment with 1.35 μM of LysSA11. The data presented here strongly suggest that the novel CBD-containing staphylococcal endolysin LysSA11 can be used both as a food antimicrobial and as a practical sanitizer for utensils.