Synergistic Antibiofilm Effect of Thymol and Piperine in Combination with Aminoglycosides Antibiotics against Four Salmonella enterica Serovars

Table 2

Minimum biofilm inhibitory concentration (MBIC) and effects of the combination of thymol/piperine with amikacin, kanamycin, and streptomycin against biofilm formation of four Salmonella enterica serovars.

Isolates	Antibiotics	MBIC (µg/mL)							MBIC reduction fold (antibiotic)		FICI/INT
		Alone			Combined
		ATB	Thy	Pip	ATB/Thy	Thy	ATB/Pip	Pip	ATB/Thy	ATB/Pip	ATB/Thy	ATB/Pip
S. Typhi ATCC 6539	Amikacin	8	256	1024	0.5	32	1	512	16	8	0.19/S	0.63/Ad
	Kanamycin	8	256	1024	1	64	2	128	8	4	0.38/S	0.38/S
	Streptomycin	8	256	1024	0.5	256	2	1024	16	4	1.06/I	1.25/I
S. Enteritidis	Amikacin	8	1024	1024	0.25	64	0.5	512	32	16	0.09/S	0.56/Ad
	Kanamycin	8	1024	1024	8	256	2	512	1	4	1.25/I	0.75/Ad
	Streptomycin	4	1024	1024	0.5	512	0.25	256	8	16	0.63/Ad	0.31/S
S. Typhi	Amikacin	4	256	1024	0.25	64	1	512	16	4	0.31/S	0.75/Ad
	Kanamycin	8	256	1024	2	128	1	1024	4	8	0.75/Ad	1.13/I
	Streptomycin	16	256	1024	8	64	4	1024	2	4	0.75/Ad	1.25/I
S. Typhimurium	Amikacin	8	256	1024	1	8	0.5	256	8	16	0.16/S	0.31/S
	Kanamycin	8	256	1024	0.5	16	1	1024	16	8	0.13/S	1.13/I
	Streptomycin	8	256	1024	8	64	0.5	512	1	16	1.25/I	0.56/Ad
S. Choleraesuis	Amikacin	8	256	1024	0.25	64	1	256	32	8	0.28/S	0.38/S
	Kanamycin	16	256	1024	2	256	4	128	8	4	1.13/I	0.38/S
	Streptomycin	8	256	1024	0.25	64	1	512	32	8	0.28/S	0.63/Ad

MBIC: minimum biofilm inhibitory concentration, Thy: thymol, Pip: piperine, ATB/Thy: combination of antibiotic with thymol, ATB/Pip: combination of antibiotic with piperine, FICI: fractional inhibitory concentration index, INT: interpretation, S: synergy, Ad: additivity, I: indifference.