Table 2.

Antibacterial activities of R-Pro9-3 peptides in comparison with those of Pro9-3 peptides against of standard Gram-negative bacteria and carbapenem-resistant Gram-negative bacteria.

Microorganisms	Minimal Inhibitory Concentration (MIC) in μM
	Pro9-3	Pro9-3D	R-Pro9-3	R-Pro9-3D	Melittin	Imipenem	Meropenem
Standard Gram-negative bacteria
E. coli	16	8	16	8	8	0.5	0.25
A. baumannii	16	4	16	4	4	1	0.5
P. aeruginosa	64	8	64	8	16	1	1
K. pneumoniae	64	8	32	8	32	<0.25	<0.25
Carbapenem-resistant Gram-negative bacteria
CREC E1	16	8	16	8	8	>128	>128
CREC E2	16	8	16	8	8	16	16
CRAB C0	8	4	8	4	4	>128	128
CRAB C1	16	8	32	8	4	>128	>128
CRAB C2	16	8	32	4	4	>128	128
CRAB C3	16	8	32	8	4	128	128
CRAB C4	16	8	32	4	4	128	>128
CRAB C5	16	8	32	4	4	128	>128
CRAB C6	16	8	32	4	4	128	>128
CRAB C7	16	8	32	4	4	128	128
CRAB C8	16	8	32	4	4	>128	>128
CRAB C9	16	8	16	4	4	>128	>128
CRAB C10	16	8	16	4	4	>128	>128
CRKP K1	64	16	32	16	64	32	64
CRKP K2	64	8	32	8	64	>128	>128
a GM	25.6	8.0	27.4	6.3	13.1	90.3	91.9
b HC10	200	200	200	200	3.1	na	na
c Relative selective index	7.8	25.0	7.3	31.7	0.2	na	na

^a The geometric means (GM) are the mean minimum inhibitory concentrations (MICs) values of all bacterial strains. ^b HC₁₀ is the degree of peptide concentration inducing 10% hemolysis of heparinized sheep red blood cells in vitro. ^c Relative selective index is the minimal peptide concentration that produces 10 percent hemolysis. When no detectable hemolysis was observed at 100 μM, a value of 200 μM was used to calculate the selective index and was calculated using HC₁₀/GM of the MIC (μM). The larger values indicate greater cell selectivity and na, not applicable. CREC, Carbapenem-resistant E. coli; CRAB, Carbapenem-resistant A. baumannii; CRKP, Carbapenem-resistant K. pneumoniae.