Melcrova, A. | bioRxiv Science

bioRxiv2025

Treating the untreatable: Reversing β-lactam resistance in MRSA by membrane-domain-dissolving antibiotics

Antimicrobial resistance is one of the most serious threats to global health with methicillin-resistant Staphylococcus aureus (MRSA) being the leading Gram-positive pathogen. Recently we discovered a new antimicrobial target for small antibiotics -- dissolution of functional domains in the bacterial membrane without pore formation. Here we apply this mechanism to reverse {beta}-lactam resistance in MRSA. We show that supplementation with a membrane-domain-dissolving antibiotic lowers the susceptibility of both a MRSA clinical isolate and the methicillin-susceptible S. aureus (MSSA) to multiple {beta}-lactams several folds. In particular, full reversal of resistance to oxacillin and penicillin in MRSA is achieved. We provide evidence on the nano-scale (atomic force microscopy), living bacteria (fluorescence microscopy), and bacterial cultures (microbiology assays) that the {beta}-lactam resistance reversal is linked to dissolution of membrane domains. A general nature of this principle is expected, and could be applied using various membrane-domain-dissolving antibiotics to reverse {beta}-lactam resistance in various bacteria. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/684379v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@1608f24org.highwire.dtl.DTLVardef@55b460org.highwire.dtl.DTLVardef@b54337org.highwire.dtl.DTLVardef@4fef04_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOTOC Figure:C_FLOATNO Model of -lactam susceptibility renewal in MRSA based on data presented in this study. C_FIG

biophysics↗

bioRxiv2023

Lateral membrane organization as target of an antimicrobial peptidomimetic compound

Antimicrobial resistance is one of the leading concerns in medical care. Here we resolve the functional mechanism of the antimicrobial action of the cationic tripeptide AMC-109 by combining high speed-atomic force microscopy, molecular dynamics, fluorescence assays, and lipidomic analysis. We show that AMC-109 activity on the negatively charged plasma membrane of Staphylococcus aureus consists of two crucial steps. First, AMC-109 self-assembles into stable aggregates with specificity for negatively charged membranes. Second, by incorporation into the S. aureus membrane the lateral membrane organization is affected, dissolving membrane nanodomains. Domain dissolution affects membrane functions such as protein sorting and cell wall synthesis, and is suggested to cause a loss of resistance of methicillin-resistant S. aureus (MRSA) to methicillin. As the AMC-109 mode of action is similar to the activity of the disinfectant benzalkonium chloride (BAK), a broad applicability, but with low cytotoxicity to human cells, is expected.

biophysics↗