Table 3.
Minimum inhibitory concentration (MIC) of α-helical peptide derivatives against 12 strains of human pathogenic Gram-positive and -negative bacteria.
| MIC (µg/ml) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| P0 | P7 | A0 | A3 | P7A3 | PA-18 | PA-17 | PA-16 | PA-15 | PA-14 | PA-13 | Melittin | |
| Gram-negative bacteria | ||||||||||||
| Pseudomonas aeruginosa ATCC 27853 | >250 | 7.81 | >250 | >250 | 7.81 | 7.81 | 7.81 | 7.81 | 7.81 | 3.91 | 3.91 | 15.63 |
| Escherichia coli ATCC 25922 | >250 | 15.63 | >250 | >250 | 15.63 | 31.25 | 15.63 | 7.81 | 15.63 | 15.63 | 31.25 | 31.25 |
| Escherichia coli O157:H7 MT strain | >250 | 125 | >250 | >250 | 250 | 250 | 62.5 | 62.5 | 15.63 | 62.5 | 31.25 | 7.81 |
| Shigella sonnei ATCC 11060 | >250 | 3.91 | >250 | >250 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 |
| Salmonella Typhimurium ATCC 13311 | >250 | 7.81 | >250 | >250 | 7.81 | 3.91 | 3.91 | 1.95 | 1.95 | 1.95 | 1.95 | 3.91 |
| Vibrio cholera O1 Inaba DMST 16261 | >250 | 31.25 | >250 | >250 | 7.81 | 7.81 | 7.81 | 3.91 | 3.91 | 7.81 | 31.25 | 3.91 |
| Acinetobacter baumannii MT strain | >250 | 7.81 | >250 | >250 | 7.81 | 15.63 | 7.81 | 7.81 | 3.91 | 3.91 | 7.81 | 7.81 |
| Gram-positive bacteria | ||||||||||||
| Staphylococcus aureus ATCC 25923 | >250 | 62.5 | >250 | >250 | 15.63 | 15.63 | 15.63 | 7.81 | 7.81 | 15.63 | 62.5 | 3.91 |
| Staphylococcus epidermidis ATCC 12228 | >250 | 3.91 | >250 | >250 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 |
| Bacillus cereus ATCC 11778 | >250 | 31.25 | >250 | >250 | 7.81 | 7.81 | 7.81 | 3.91 | 3.91 | 7.81 | 15.63 | 3.91 |
| Enterococcus faecalis ATCC 29212 | >250 | >250 | >250 | >250 | 31.25 | 31.25 | 31.25 | 15.63 | 31.25 | 125 | 250 | 1.95 |
| Listeria monocytogenes 10403 s | >250 | 7.81 | >250 | 250 | 3.91 | 1.95 | 1.95 | 3.91 | 1.95 | 1.95 | 3.91 | 3.91 |
| MHCa (µg/ml) | >250 | 250 | >250 | >250 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 15.63 | 125 | ˂0.98 |
| GMb (Gr.− strains) | >250 | 28.46 | >250 | >250 | 42.97 | 45.76 | 15.63 | 13.67 | 7.54 | 14.23 | 15.90 | 10.60 |
| Therapeutic index (TI)c (Gr.− strains) | 1.00 | 8.78 | 1.00 | 1.00 | 0.09 | 0.09 | 0.25 | 0.29 | 0.52 | 1.10 | 7.86 | 0.05 |
| GMd (Gr.+ strains) | >250 | 121.09 | >250 | >250 | 12.50 | 12.11 | 12.11 | 7.03 | 9.77 | 30.86 | 67.19 | 3.52 |
| Therapeutic index (TI)e (Gr.+ strains) | 1.00 | 2.06 | 1.00 | 1.11 | 0.31 | 0.32 | 0.32 | 0.56 | 0.40 | 0.51 | 1.86 | 0.14 |
aMHC is the minimum concentration that caused 10% hemolysis of human red blood cells (hRBC). When no 10% hemolysis was observed at 250 µg/ml, a value of 500 µg/ml was used to calculate the therapeutic index.
bGM (Gr.- strains) denotes the geometric mean of MIC values from all Gram-negative strains.
cTherapeutic index (Gr.- strains) is the ratio of the MHC to the geometric mean of MICs from Gram-negative strains.
dGM (Gr.+ strains) denotes the geometric mean of MIC values from all Gram-positive strains.
eTherapeutic index (Gr.+ strains) is the ratio of the MHC to the geometric mean of MICs from all Gram-negative strains.