Fig. 5.

Synergistic action of lugdunin and human antimicrobial peptides (AMPs) kills methicillin-resistant S. aureus (MRSA). a, c Logarithmically grown (3 × 10⁶) S. aureus were incubated with indicated combinations of lugdunin and human AMPs in phosphate-buffered saline (PBS) containing 0.1% tryptic soy broth (TSB) at 37 °C orbital shaking (white bar, untreated; dark gray bars, AMP treatment; middle gray bars, lugdunin treatment; light gray bars, AMP and lugdunin combination treatment). After 3 h of incubation, several dilutions of the bacterial suspensions were plated onto TSB agar plates and incubated overnight at 37 °C. The next day S. aureus colony-forming units (CFUs) were counted. Each experiment was performed in triplicates. Data represent the percentage of CFU of at least three independent experiments normalized to the untreated control ± s.e.m. Significant differences to control treatments were analyzed by ordinary one-way analysis of variance (ANOVA) followed by Dunnett’s multiple comparisons test (*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001). b Combination indices (CIs) were calculated using CompuSyn (ComboSyn Inc.) and indicated in median effect plots as a function of the bacteria fractions affected by the combinatorial peptide treatment. CI values of 1 indicate additive effects, whereas values <1 and >1 indicate synergistic and antagonistic effects, respectively. Source data are provided as a Source Data file