TABLE 2.

FICs of natural fish antibiotics^a

Antibiotic	MIC (μg/ml)	FIC (μg/ml) with HSDF-1 concn (μg/ml) of:		FIC index with HSDF-1	FIC (μg/ml) with HSDF-2 concn (μg/ml) of:		FIC index with HSDF-2
		32	128		32	128
None
A. salmonicida		>1,024	>1,024		>1,024	>1,024
V. anguillarum		>1,024	>1,024		>1,024	>1,024
Pleurocidin
A. salmonicida	2	0.125	<0.12	<0.08	0.125	<0.12	<0.09
V. anguillarum	16	8	4	<0.31	4	1	<0.19
Hen egg white lysozyme (V. anguillarum)	>256	128	32	<0.25	128	64	<0.38
Mucus (V. anguillarum)b	>256	256	32	<0.25	256	64	<0.38
Serum (V. anguillarum)b	>256	128	32	<0.19	128	32	<0.25

^aInhibitory concentrations of natural fish antibiotics, as well as hen egg white lysozyme, in the presence of HSDF-1 or HSDF-2 are shown. Two concentrations of each histone peptide are presented for two separate bacteria: V. anguillarum and A. salmonicida. FIC indices for natural fish antibiotics and histone peptides have been calculated according to the previously described formula and are shown. See text for details of calculations. 

^bValues are lysozyme concentrations in mucus or serum. Estimates of lysozyme concentration in the extracts were performed using a standard M. lysodeikticus assay (22).