Table 2. Summary of the Potentiating Effects of Outer Membrane Permeabilizers.

no.	OM permeabilizers	molecular structure	combined drug	microbial species	proposed mechanisms	MICa of drug alone	MICa in combination	fold decrease	FIC	ref
a	pentamidine	Scheme 2a	novobiocin	A. baumannii	displace the ion cross-linkers in the OM	12	<0.2	>60	<0.258	(56)
b	colistin	Scheme 2b	rifampicin	P. aeruginosa	displace the ion cross-linkers in the OM	64	4	16	0.31	(59)
c	PMBN	Scheme 2c	fusidic acid	E. coli	displace the ion cross-linkers in the OM	100	1	100	<0.03	(67)
d	SPR741	Scheme 2d	rifampicin	A. baumannii.	displace the ion cross-linkers in the OM	4	0.5	8	0.14	(71)
e	SLAP-S25	Scheme 2e	colistin	Providencia alcalifaciens	displace the ion cross-linkers in the OM	16	0.016	1000	0.002	(73)
f	thanatin	Scheme 1k	meropenem	E. coli	sequester the ion cross-linkers in the OM	144*	18*	8	0.625	(42)
g	LABv2.1	Scheme 2f	erythromycin	E. coli	target 1-phosphor-GlcNAc of lipid A	200	<0.2	>1000	<0.251	(75)
h	LL-37	N.D.	histone	E. coli	pore formation in the OM and IM	N.A.b	N.A.b	N.A.b	N.A.b	(79)
i	PAS8-b-PDM12	Scheme 2g	rifampicin	E. coli	target lipid A in the OM	12.5	0.25	50	0.25	(82)
j	2,6-DAC	Scheme 2h	novobiocin	A. baumannii	enhance antibiotic penetration	8	0.5	16	0.312	(83)

^aThe MIC is given as μg/mL, except when specified by “*”, which indicates that the MIC is given as μM.

^bThe synergy was determined by the time-killing method; N.D., not determined; N.A., not available. OM, outer membrane; IM, inner membrane.