Table 2.

Fractional inhibitory concentration index (FICI) for antibiotics paired with LL-37 against E. coli and P. aeruginosa lab strains.

	FICI
Bacterial Strain	Ampicillin	Tetracycline	Ciprofloxacin	Gentamicin	Aztreonam	Polymyxin B
E. coli MG1655	1	1	0.5	1	0.75	0.37
P. aeruginosa PAO1	n.d.	0.56	0.56	1.5	2	0.31

FICI ≤ 0.5 is synergistic, 0.5 < FICI ≤ 1.0 is additive, 1.0 < FICI ≤ 4.0 is indifferent, and FICI > 4.0 is antagonistic. n.d.: not determined.