. 2023 Apr 18;11(3):e04702-22. doi: 10.1128/spectrum.04702-22

TABLE 2.

Baicalein enhances the antimicrobial activity of doxycycline against Gram-negative pathogens

Strain	Genotype^a	Resistance pattern	Doxycycline		Baicalein		FICI^b
Strain	Genotype^a	Resistance pattern	MIC (μg/mL)	FIC	MIC (μg/mL)	FIC	FICI^b
A. baumannii
AB9	tetA⁺ tetB⁺	MDR	128	0.0625	250	0.25	0.3125
AB24	tetB ⁺	PDR	128	0.125	500	0.25	0.375
AB27	tetA⁺ tetB⁺	MDR	128	0.03125	250	0.125	0.15625
AB32	tetA⁺ tetB⁺	PDR	128	0.25	250	0.25	0.5
AB43	tetA tetB	Sensitive	1	0.25	250	0.125	0.375
AB145	tetA ⁺	MDR	128	0.03125	250	0.0625	0.09375
AB146	tetB⁺	PDR	128	0.25	250	0.125	0.375
AB151	tetA tetB	PDR	64	0.125	500	0.125	0.25
AB152	tetA⁺ tetB⁺	MDR	64	0.03125	500	0.25	0.28125
ATCC 19606	tetA tetB	Type strain, non-MDR	1	0.25	250	0.25	0.5
K. pneumoniae
KP1	tetA ⁺	MDR	128	0.125	250	0.0625	0.1875
KP2	tetA ⁺	PDR	128	0.25	500	0.125	0.375
KP6	tetA ⁺	PDR	64	0.125	500	0.25	0.375
KP10	tetA ⁺	MDR	64	0.0625	125	0.125	0.1875
KP12	tetA ⁺	MDR	64	0.03125	250	0.25	0.28125
KP13	tetA ⁺	PDR	64	0.0625	500	0.25	0.3125
KP14	tetA ⁺	PDR	32	0.125	500	0.25	0.375
KP15	tetA ⁺	MDR	32	0.125	250	0.125	0.25
E. coli
E.col-1	tetA ⁺	MDR	32	0.125	250	0.25	0.375
E.col-2	tetA ⁺	MDR	64	0.0625	500	0.0625	0.125
E.col-3	tetA ⁺	MDR	32	0.125	250	0.125	0.25
P. aeruginosa
PA-1	tetA ⁺	MDR	64	0.125	250	0.125	0.25
PA-2	tetA ⁺	MDR	128	0.125	500	0.125	0.25

+, presence; no symbol, absence.

The FICI is the sum of the FICs of doxycycline and baicalein. All effects shown here are defined as synergistic (FICI ≤ 0.5).