Characterizations of the endolysin Lys84 and its domains from phage qdsa002 with high activities against Staphylococcus aureus and its biofilms.

Staphylococcus aureus (S. aureus), particularly methicillin-resistant S. aureus (MRSA), and its biofilms are great threats in the food industry. Bacteriophage-encoded endolysins are promising tools to inhibit pathogens and to eliminate their biofilms. In this work, a virulent phage qdsa002 against S. aureus ATCC43300 (MRSA) was isolated, and the phage's endolysin (Lys84) and its domains were expressed and purified. Morphological and genome analyses demonstrated that qdsa002 is a Twort-like phage from Myoviridae. Lys84 contains two catalytic domains (CHAP and Amidase_2) and one cell binding domain (SH3b). This endolysin exhibits a strong lytic activity against S. aureus and has a wider bactericidal spectrum than qdsa002. Moreover, Lys84 exceed 10 μM effectively removed around 90 % of the biofilms of S. aureus. Besides, CHAP and Amidase_2 domains remained 61.20 % and 59.46 % of lytic activity as well as 84.31 % and 70.11 % of anti-biofilm activity of Lys84, respectively. The lytic and anti-biofilm activities of the combination of CHAP and Amidase_2 were close to 90 % of those of Lys84. These results indicated that Lys84 and its domains might be alternative antimicrobials for controlling S. aureus and its biofilms.