TABLE 3.

Synergistic effects of S1, S1-Nal, and S1-Nal-Nal in combination with antibiotics against bacterial strains studied.

Strains	Antibiotics (μg/mL)	AMP (μg/mL) (¼ × MIC)
		S1		S1-Nal		S1-Nal-Nal
		+	FICIa	+	FICI	+	FICI
Enterococcus faecium BCRC 15B0132	Vancomycin	>64	1.25	8	0.31	2	0.27
	Ciprofloxacin	64	0.75	16	0.38	2	0.27
	Tetracycline	16	0.5	8	0.38	1	0.27
Acinetobacter baumannii BCRC 14B0091	Vancomycin	16	0.38	2	0.27	>64	1.25
	Ciprofloxacin	32	0.5	32	0.5	64	2.25
	Tetracycline	64	0.75	32	0.5	>64	1.25
Acinetobacter baumannii BCRC 14B0097	Vancomycin	32	0.5	2	0.27	2	0.27
	Ciprofloxacin	>64	1.25	64	0.75	2	0.27
	Tetracycline	64	0.75	64	0.75	2	0.27
Acinetobacter baumannii BCRC 14B0100	Vancomycin	32	0.5	2	0.27	4	0.28
	Ciprofloxacin	64	0.75	32	0.5	32	0.75
	Tetracycline	64	0.75	64	0.75	>64	1.25
Escherichia coli BCRC 13B0198	Vancomycin	32	0.5	32	0.5	32	0.5
	Ciprofloxacin	2	0.27	2	0.27	2	0.31
	Tetracycline	>64	1.25	64	0.75	64	0.75
Escherichia coli BCRC 13B0207	Vancomycin	64	0.75	>64	1.25	64	0.75
	Ciprofloxacin	0.02	0.31	0.06	0.5	0.13	0.75
	Tetracycline	64	0.75	64	0.75	64	0.75

^aFICI, fractional inhibitory concentration index, FICI ≤ 0.5, synergy; 0.5 < FICI ≤ 4, no interaction; FICI > 4, antagonism.

+, the MIC of antibiotic in combination with ¼ × MIC antimicrobial peptides (AMPs). Bold values indicated synergistic effects.