TABLE 2.

Inhibitory concentrations of DCD-1L, SSL-25, and LL-37 on S. aureus 113 wild-type strain and mutants lacking cell envelope modifications

S. aureus strainaIC90 (μg/ml)b
DCD-1LSSL-25LL-37
113 wild type12.5 (±0.7)12 (±2.8)0.6 (±0.2)
113 Δatl8 (±2.4)8 (±2.8)0.5 (±0.1)
113 Δsrt11 (±1.4)9 (±1.4)0.7 (±0.1)
113 ΔspA9.5 (±0.7)9 (±1)1.5 (±0.7)
113 ΔypfP12 (±1.7)10 (±0.3)0.5 (±0.1)
113 ΔtagO18 (±1.7)15 (±1)1.5 (±0.7)
  • a The following defined S. aureus mutants were used: Δatl mutant, deficient in autolysin; Δsrt mutant, deficient in sortase; ΔspA mutant, deficient in protein A; ΔypfP mutant, reduced level of LTA; ΔtagO mutant, deficient in WTA.

  • b IC90 designates the concentration of peptide in μg/ml able to kill 90% of the microorganisms (1 × 106 CFU/ml) in 10 mM sodium phosphate-10 mM NaCl in a CFU assay compared to the control incubated only in buffer without peptide. The values are means ± standard deviations of at least three independent experiments. There is no significant change of antimicrobial activity for the mutant strains compared to the wild-type S. aureus strain 113 (P > 0.05).