Table 1. Minimal inhibitory concentrations and minimal bactericidal concentration of peptides against standard bacterial strains.
| Gram-negative | Gram-positive | ||||||
|---|---|---|---|---|---|---|---|
| MIC (MBC)a (μM) | MIC (MBC) (μM) | ||||||
| Bacterial strains | Cecropin DH | Cecropin B | Melittin | Bacterial strains | Cecropin DH | Cecropin B | Melittin |
| E. coli ATCC25922 | 3.13 (6.25) | 1.56 (1.56) | 6.25 (6.25) | B. subtilis | 3.13 (3.13) | 6.25 (6.25) | 1.56 (1.56) |
| E. coli DH5α | 1.56 (3.13) | 0.78 (0.78) | 3.13 (6.25) | S. aureus | >100 (>100) | >100 (>100) | 3.13 (3.13) |
| P. aeruginosa | 6.25 (12.5) | 3.13 (12.5) | 6.25 (25) | M. luteus | 1.56 (1.56) | 0.78 (0.78) | 3.13 (3.13) |
| GMb | 3.65 | 1.82 | 5.21 | GM | 68.23 | 69.01 | 2.61 |
| MHCc | 400 | 400 | 0.78 | MHC | 400 | 400 | 0.78 |
| Therapeutic indexd (MHC/GM) | 109.59 | 219.78 | 0.15 | Therapeutic indexd (MHC/GM) | 5.86 | 5.80 | 0.30 |
Notes:
a
MICs was determined as the lowest concentration of peptides that prevented visible turbidity. MBC was taken to be the lowest concentration of peptides that prevent any residual colony formation. When no antimicrobial activity was observed at 100 μM, a value of 200 μM was used to calculate the therapeutic index.
b
The geometric mean (GM) of the MIC was obtained from bacterial strains are shown.
c
The MHC is the minimum hemolytic concentration that caused 10% hemolysis of mouse red blood cells (mRBCs). The MHC value of melittin is from reference (Kim et al., 2011). When it did not reach 10% hemolysis at 200 μM, a value of 400 μM was used to calculate the therapeutic index.
d
Therapeutic index is the ratio of the MHC value over GM.