TABLE 1.

Effects of antimicrobial agents on MP and permeability of S. aureus

Drug	MIC (μg/ml)	Dose (μg/ml)	Drug effect
			MP	Permeability
Amoxicillin	1.0	0.25, 0.5	Little or no change	At 2 h, 33% permeabilized; at 3 to 4 h, <8% permeabilized
		1.0	At 3 h, >99% depolarized	At 3 h, 69% permeabilized
		4.0	At 3 h, >99% depolarized	At 3 h, 29% permeabilized
Chloramphenicol	NDa	4.0b	No change after 4 h	No change after 4 h
Erythromycin	4.0	<1.0	No change after 4 h	No change after 4 h
		4.0	Depolarization by 4 h	20% permeabilized at 4 h
Streptomycin	ND	5.0b	Depolarization by 1 h	No change after 4 h
Tetracycline	0.25	<1.0	No change after 4 h	No change after 4 h
		4.0	Depolarization by 4 h	50% permeabilized at 4 h

^aND, not determined. 

^bThe dose completely inhibited bacterial growth.