Table 4. Susceptibility of bacitracin-treated and vraDE-overexpressing S. aureus to nisin A and nukacin ISK-1.

		MIC (mg/L)
Strain	Relevant Genotype	Bacitracin (−)		Bacitracin (+)
		Nisin A	Nukacin ISK-1	Nisin A	Nukacin ISK-1
MW2	Wild-type	6.4	64	12.8	128
FK64	ΔapsRS in MW2	3.2	32	12.8	128
FK72	ΔvraSR in MW2	6.4	32	12.8	128
FK77	ΔbraRS in MW2	3.2	16	3.2	16
		IPTG (–)		IPTG (+)
Strain	Relevant Genotype	Nisin A	Nukacin ISK-1	Nisin A	Nukacin ISK-1
MM31	vraDE in FK64	3.2	32	12.8	128

Expression of braR, graR, vraR, braA, vraD, and vraF was determined using the method described in the Materials and Methods. (A) braA, vraF, vraD, braR, graR, and vraR expression in S. aureus MW2 exposed to various concentrations of nisin A (5 min exposure). *, statistically significant difference from the wild-type as tested using Dunnett’s method (p<0.05). (B) Time course experiment of braA, vraF, and vraD expression in S. aureus MW2 exposed to nisin A (16 µg/ml). (C) braA, vraF, and vraD expression in S. aureus MW2 and three mutants (braRS, graRS, and vraSR mutant) exposed to nisin A (16 µg/ml). *, statistically significant difference from the wild-type as tested using Dunnett’s method (p<0.05).