Antibiotic-Potentiating Effect of Some Bioactive Natural Products against Planktonic Cells, Biofilms, and Virulence Factors of Pseudomonas aeruginosa

Table 3

Mean of the minimum biofilm inhibitory concentration (MBIC), fractional inhibitory concentration (FIC), and fractional inhibitory concentration index (FICI) of antibiotics (ATB) and natural products (NPs) in combination against nineteen P. aeruginosa isolates.

Antimicrobial agent combination	MBIC (μg/mL)				FIC		MBIC reduction fold of ATB	FICI/interpretation
	Alone		Combined
	ATB	NPs	ATB	NPs	ATB	NPs
Cef+Cur	175.16	566.21	43.79	168.42	0.25	0.30	4.00	0.55/A
Cef+Pip	175.16	>2048	78.32	592.84	0.45	0.29	2.24	0.74/A
Cef+Plu	175.16	>1280	64.84	646.74	0.37	0.51	2.70	0.88/A
Cef+Thy	175.16	464.84	50.95	148.21	0.29	0.32	3.44	0.61/A
Cef+Que	175.16	52.21	73.68	22.32	0.42	0.43	2.38	0.85/A
Cef+Sin A	175.16	74.11	29.89	13.68	0.17	0.18	5.86	0.36/S
Ami+Cur	45.47	566.21	8.74	83.26	0.19	0.15	5.20	0.34/S
Ami+Pip	45.47	>2048	15.68	350.32	0.34	0.17	2.90	0.52/A
Ami+Plu	45.47	>1280	24.42	794.95	0.54	0.62	1.86	1.16/I
Ami+Thy	45.47	464.84	15.58	162.53	0.34	0.35	2.92	0.69/A
Ami+Que	45.47	52.21	4.42	14.11	0.10	0.27	10.29	0.37/S
Ami+Sin A	45.47	74.11	1.38	5.37	0.03	0.07	32.95	0.10/S
Nor+Cur	106.95	566.21	7.77	42.95	0.07	0.08	13.76	0.15/S
Nor+Pip	106.95	>2048	49.68	485.05	0.46	0.24	2.15	0.70/A
Nor+Plu	106.95	>1280	50.53	848.84	0.47	0.66	2.12	1.14/I
Nor+Thy	106.95	464.84	30.32	104.42	0.28	0.22	3.53	0.51/A
Nor+Que	106.95	52.21	14.95	14.11	0.14	0.27	7.15	0.41/S
Nor+Sin A	106.95	74.11	8.42	13.89	0.08	0.19	12.70	0.27/S

ATB: antibiotics; NPs: natural products; MBIC: minimum biofilm inhibitory concentration; Cef: ceftazidime; Ami: amikacin; Nor: norfloxacin; Cur: curcumin; Pip: piperine; Plu: plumbagin; Thy: thymol; Que: quercetin; Sin A: sinapic acid; S: synergy; A: additivity; I: indifference.