The strategy of biopreservation of meat product against MRSA using lytic domain of lysin from Staphylococcus aureus bacteriophage

Abstract Staphylococcus aureus is a notorious foodborne pathogen capable of producing various toxins including heat-stable enterotoxin, forming biofilm, evolving to multidrug-resistant strains including methicillin-resistant S. aureus (MRSA) against antibiotics, and threatening public health, of which the biocontrol garners increasing interest from both researchers and food industry. Recently, bacteriophage lysins, degrading cell wall that is indispensable for bacteria, are deemed promising antimicrobial agents. In this work, the lysin LysGH15 from MRSA phage GH15 demonstrated a broad lytic spectrum to S. aureus, cleaving six test S. aureus strains including MRSA, as well as its catalytic domain CHAPLysGH15 alone. LysGH15 and CHAPLysGH15 exhibited different characteristics to one MRSA strain (MRSA 2701), reaching the highest activity at different conditions (35 °C and pH of 6.0 for LysGH15, 40 °C and pH of 9.0 for CHAPLysGH15). Especially, the different sensitivities of two enzymes to NaCl concentration in foods were found, where 500 mM of NaCl was indispensable for LysGH15’s efficient lytic action while high concentration of NaCl impaired the activity of CHAPLysGH15. The susceptibility to NaCl and high optimal antimicrobial pH (9.0) of CHAPLysGH15 enabled its application in low-salt and non-acid foods such as fresh meat, of which the preservation is always an issue in food industry. LysGH15 and CHAPLysGH15 presented a promising biocontrol effect in high-salt food and low-salt food, respectively. The 0.4 nmol/cm2 of LysGH15 and CHAPLysGH15 were applied in Chinese bacon and fresh pork, where they could efficiently decrease MRSA from 104 to 0 CFU/cm2 after 2 h (LysGH15 to bacon, and CHAPLysGH15 to fresh pork).