Characterization and bioinformatic analysis of a new chimeric endolysin against MRSA with great stability

Antibiotics become less effective in treating infectious diseases as resistance increases. Staphylococcus aureus is a global problem due to its ability to form biofilms and resistance mechanisms. Phage endolysin is one of the most promising methods for combating antibiotic resistance. ZAM-MSC chimeric endolysin has three domains derived from SAL1 and lysostaphin, which target the peptide bridge of peptidoglycan. In this study purified ZAM-MSC (with yield of 30 mg/lit) had bactericidal activity against methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) at low concentrations (2.38 μg/ml and 1.88 μg/ml, respectively). The antibacterial spectrum revealed that ZAM-MSC was active against diverse Staphylococci. it has maintained 100% stability after 24 h incubation in pH 5 to 10 against S. aureus, as well as demonstrated significant thermostability and maintained nearly its full activity at different temperatures (4-42 °C) up to 1 day of incubation. The anti-biofilm activity of various concentrations of ZAM-MSC against MSSA and MRSA biofilms was not dose-dependent, and antibiofilm activity was observed even at low concentrations (14 μg/ml). Further, the molecular dynamics simulations demonstrated that the ZAM-MSC chimer and its parent proteins remained dynamically stable, showing similar flexibility despite the size and hydrogen bond number differences. In conclusion, the study reveals that chimeric ZAM-MSC is a distinctive enzyme with exceptional biochemical properties and rapid lytic activity against Staphylococci.