Lauric Acid Microemulsions Inhibit Staphylococcus aureus Through Cell Membrane Disruption and Potential Interference with Peptidoglycan Biosynthesis

A honokiol-derived cationic amphiphilic compound combats methicillin-resistant Staphylococcus aureus by disrupting membrane phospholipid homeostasis.

Methicillin-resistant Staphylococcus aureus (MRSA) remains a major threat owing to limited therapeutic options and increasing antimicrobial resistance. In this study, a new honokiol-derived amphiphilic compound, 5D, was developed and evaluated for its anti-MRSA activity. 5D exhibited potent activity against clinical MRSA isolates (MIC = 0.5-1 μg/mL), and rapidly killed MRSA N315 in both early and late growth phases. It also disrupted established biofilms, retained activity after plasma exposure, and showed a low propensity for resistance development. Mechanistic analyses revealed that 5D damages bacterial morphology, dissipates membrane potential, increases membrane permeability, and causes leakage of intracellular DNA and proteins. Untargeted metabolomics indicated that 5D markedly perturbs glycerophospholipid metabolism, while phospholipid supplementation and isothermal titration calorimetry suggested preferential interaction with phosphatidylglycerol. In a Galleria mellonella infection model, 5D improved 7-day survival to approximately 33% and reduced bacterial burdens by 0.7-1.2 log10 CFU/mL compared with untreated larvae. In a murine sepsis model, 5D increased survival to 83.3-100% and significantly reduced organ bacterial burdens. These findings identify 5D as a promising honokiol-derived anti-MRSA lead compound that acts mainly by disrupting membrane integrity and phospholipid homeostasis.

Chitosan-Based Composite Film Containing Cell-Free Supernatant of Lactiplantibacillus plantarum JC2211 for Chilled Pork Preservation

Traditional fermented vegetables are important resources for screening excellent antibacterial lactic acid bacteria (LAB). In this study, a strain of Lactiplantibacillus plantarum JC2211 with broad-spectrum antibacterial activity against Salmonella Typhimurium (S.T), Staphylococcus aureus (S.a), Listeria monocytogenes (L.m), and Pseudomonas aeruginosa (P.a) was isolated from Yangzhou pickles. The minimum inhibitory concentration (MIC) of its cell-free supernatant (CFS) against all four pathogens was 25 μL/mL. The strain exhibited favorable biosafety and strong environmental adaptability, tolerating 8% NaCl, pH 3.0–10.0, and 0.3% bile salt. The CFS exerted synergistic antibacterial effects via multiple pathways, including increasing cell membrane permeability, reducing membrane potential, decreasing intracellular ATP levels, and inducing ROS accumulation. Metabolite identification indicated that organic acids (dominated by D-lactic acid at 9.37%, citric acid at 8.00%, and phenyllactic acid at 4.42%) were the main components. Using chitosan (CS) as the base material, composite preservation films were fabricated by incorporating 10–50% CFS. The composite film containing 40% CFS (CS/CFS40) exhibited the optimal comprehensive performance, with ABTS and DPPH radical scavenging rates of 90.24% and 79.17%, respectively, along with satisfactory tensile strength (18.70 MPa) and elongation at break (22.93%). In chilled pork preservation, the CS/CFS40 film significantly inhibited the proliferation of spoilage microorganisms, and effectively retarded lipid oxidation. Moreover, the film suppressed the colonization of L.m and S.T on meat surfaces, with bacterial loads maintained at 2.07–2.67 lg CFU/g and 2.92–2.99 lg CFU/g, respectively, over 7 days of refrigeration. Collectively, the CS/CFS40 composite film extended the shelf life of chilled pork to approximately 6 days. This study provides a novel natural biological preservative and eco-friendly active packaging material for chilled meat preservation.

Niosomal Encapsulation of Geraniol Improves Antimicrobial Activity Against Selected Foodborne Pathogens

Phytochemical-mediated CuO nanoparticles disrupt bacterial membranes and promote dermal fibroblast migration.

Chronic wound repair is frequently impaired by bacterial infection, creating a need for antibacterial materials that can suppress microbial growth without compromising skin-cell function. In this study, phytochemical-mediated copper oxide nanoparticles (CuO NPs) were synthesized using Aegle marmelos leaf extract and investigated for their antibacterial mechanism and effects on adult dermal fibroblasts. Structural and surface analyses confirmed the formation of monoclinic CuO NPs with particle dimensions of approximately 18-22 nm, Cu2+-rich surface states, and oxygen-containing phytochemical functionalities. The CuO NPs exhibited concentration-dependent antibacterial activity against Escherichia coli and Staphylococcus aureus, with S. aureus displaying greater susceptibility. Colony-forming unit analysis confirmed a marked reduction in bacterial survival. Ultrastructural examination revealed close nanoparticle cell association, deformation of the bacterial envelope, membrane discontinuity, and loss of intracellular contents. Consistently, increased extracellular nucleic-acid release demonstrated that the antibacterial activity was associated with disruption of membrane integrity and increased cellular permeability. The nanoparticles additionally exhibited concentration-dependent radical-scavenging activity, indicating retention of redox-active phytochemical constituents on their surfaces. At biologically compatible concentrations, the CuO NPs maintained adult dermal fibroblast viability and enhanced fibroblast migration in an in vitro scratch assay. The concentration-dependent erythrocyte response observed in the hemolysis assay emphasized the importance of dose optimization. Collectively, these findings demonstrate that phytochemical-mediated CuO NPs combine membrane-disruptive antibacterial activity with fibroblast-compatible, migration-supporting effects, supporting their further investigation as bioactive materials for infected wound management.

Characterization of a lytic Staphylococcus aureus phage JAsa55 and its biocontrol potential in milk.

Staphylococcus aureus (S. aureus) is a prominent foodborne pathogen that frequently causes food poisoning by contaminating various foods, particularly dairy products, and poses severe threats to food safety and public health. The increasing prevalence of multidrug-resistant S. aureus strains has further limited the efficacy of conventional interventions. In this study, we isolated and characterized a novel lytic phage JAsa55 using an MDR S. aureus strain as host. Transmission electron microscopy showed that JAsa55 possesses an icosahedral head and a long non-contractile tail, consistent with a siphovirus-like morphology. Notably, JAsa55 retained detectable activity after exposure to 4-60°C and remained active under pH 3.0-11.0. One-step growth analysis indicated a latent period (15 min) and an estimated burst size (∼500 PFU/cell) based on the first rise phase. Genome annotation did not identify obvious integrase genes, known virulence factors, or antimicrobial-resistance genes. In artificially contaminated milk, phage JAsa55 reduced S. aureus populations by up to ∼1.6 log CFU/mL at 4°C and ∼3.3 log CFU/mL at 25°C within 24 h. These findings suggest that JAsa55 has lytic activity against selected MDR S. aureus strains and may be further evaluated as a candidate component for phage-based control strategies in milk.

Antibiofilm activity of a recombinant mussel-derived antimicrobial protein through surface charge-mediated hydration layer formation.

Biofilm formation on biomedical devices remains a major cause of persistent infections and antibiotic resistance. In this study, we developed a charge-mediated, anti-adhesive platform by immobilizing recombinant mussel adhesive protein-antimicrobial peptide fusions (MAP-AMPs) on solid substrates via a simple EDC/NHS covalent coupling reaction. Using recombinant MAP-foot protein-151 (MAP-fp-151) as a versatile scaffold, immobilized MAP-AMPs were characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and Coomassie brilliant blue staining. While soluble MAP-AMPs exhibited potent bactericidal activity against both reference and antibiotic-resistance clinical E. coli strains, their immobilized forms primarily inhibited biofilm formation rather than exhibiting direct bactericidal activity. Computational simulations and experimental surface analyses revealed that the cationic MAP-AMPs formed island-like clusters that elevated surface positive potential and organized a dense, long-range hydration layer extending beyond the clusters into the bare surface regions. This mechanism was experimentally validated using Kelvin probe force microscopy (KPFM) and contact angle analysis, which showed elevated surface potential, increased water retention, and reduced water contact angles. Bacterial adhesion on the MAP-AMP2-immobilized surface was significantly suppressed, with adhesion rates reduced to 27.62-45.16% across all tested strains. These results indicate that MAP-AMP-immobilized surfaces provide a versatile, biocompatible, and resistance-independent strategy for preventing biofilm formation through charge-mediated hydration, offering broad potential for biomedical device coatings and antifouling applications.