TABLE 3.

Comparison of radial diffusion and broth microdilution assays^a

Organism	MIC (μg/ml) by the following assay with the indicated medium:
	LL-37			PG-1
	Radial diffusion assay with 100 mM NaCl	Broth microdilution with refined MHB	Broth microdilution with standard MHB	Radial diffusion assay with 100 mM NaCl	Broth microdilution with refined MHB	Broth microdilution with standard MHB
E. coli ML-35p	7.6	6.0–8.0	24–32	0.7	0.75–1.0	2.0–3.0
P. aeruginosa MR 3007	3.8	8.0–12.0	>32	0.7	1.5–2.0	6.0–8.0
B. subtilis	0.5	0.18–0.25	2.0–3.0	0.3	0.023–0.03	0.5–0.75
S. aureus 930918-3	9.2	2.0–3.0	>64	0.7	0.375–0.5	4.0–6.0

^aBroth microdilution assays were performed according to NCCLS guidelines with standard MHB or MHB that had been refined by anion-exchange chromatography, as described in the text. Two concentrations are given for broth microdilution results. The lower one is the highest concentration that allowed growth, and the higher one is the lowest concentration that prevented it, i.e., the MIC. By subculturing the MIC wells, we determined that these MICs corresponded to minimal bactericidal concentrations. Radial diffusion assays were performed with 5-μl samples.