Inhibiting Peptidoglycan Hydrolase Alleviates MRSA Pneumonia Through Autolysin-Mediated MDP-NOD2 Pathway

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a cause of staph infection that is difficult to treat because of resistance to some antibiotics. A recent study indicated that diarylurea ZJ-2 is a novel antibacterial agent against multi-drug resistant Enterococcus faecium . In this work, we refined the bactericidal mechanism of ZJ-2 as a peptidoglycan (PG) hydrolase by affecting AtlA-mediated PG homeostasis. Methods: A wild-type strain (WT) and a mutant strain (Δ atlA ) were used to investigate the effects of ZJ-2 on the cell wall, PG, and autolysin regulatory system by antimicrobial susceptibility testing, hemolytic toxin assay, microanalysis, autolysis assay, qRT-PCR, ELISA and mouse model of pneumonia. Results: The results revealed that ZJ-2 down-regulated the expression of genes related to peptidoglycan hydrolase (PGH) ( sprX, walR, atlA , and lytM ), and reduced the levels of PG, muramyl dipeptide (MDP), cytokines, and hemolytic toxin, while Δ atlA interfered with the genes regulation and PG homeostasis. In the mouse MRSA pneumonia model, the same trend was observed in the nucleotide oligomerization domain protein 2 (NOD2) and relative proinflammatory factors. Conclusion: ZJ-2 may act as a novel inhibitor of PG hydrolyse, disrupting autolysin-mediated PG homeostasis, and reducing inflammation by down-regulating the MDP-NOD2 pathway.