TABLE 1.

Oxacillin MICs and FICs in the presence of vancomycin determined by E-test and checkerboard titration

Species	MIC (μg/ml) by E-test			Value by checkerboard titrationa
	Vancomycin alone	Oxacillin alone	Oxacillin with vancomycinb	FIC index	Synergy
S. epidermidis	2	24	0.5 (1)	NDc	ND
S. epidermidis	3	>256	0.38 (1)	0.56	No
S. epidermidis	3	>256	0.75 (1)	0.13	Yes
S. epidermidis	3	64	0.38 (1)	0.63	No
S. epidermidis	3	>256	3 (1)	0.26	Yes
S. epidermidis	3	>256	48 (2)	ND	ND
S. epidermidis	2	3	0.19 (1.5)	0.63	No
S. epidermidis	2	24	1 (0.75)	0.38	Yes
S. epidermidis	1.5	>256	0.5 (0.75)	0.27	Yes
S. epidermidis	2	32	0.75 (0.75)	0.31	Yes
S. epidermidis	1.5	64	0.5 (0.75)	0.27	Yes
S. epidermidis	2	3	0.5 (1)	0.75	No
S. epidermidis	3	3	0.5 (1.5)	0.28	Yes
S. epidermidis	2	32	0.5 (0.75)	0.28	Yes
S. haemolyticus	2	>256	0.38 (1)	0.28	Yes
S. hominis	3	>256	0.5 (1)	0.26	Yes
S. hominis	ND	ND	ND (ND)	0.33	Yes
S. aureus	1	24	0.25 (0.5)	0.5	Yes
S. aureus	1.5	64	6 (0.5)	0.27	Yes
S. aureus	1	>256	128 (0.5)	0.53	No
S. aureus	0.5	>256	>256 (0.25)	1	No
S. aureus	1	48	6 (0.5)	0.31	Yes
S. aureus	1.5	>256	64 (0.5)	0.53	No

^aFIC index indicates synergy when value is ≤0.5 or antagonism when value is >4. 

^bValues in parentheses are concentrations (micrograms per milliliter) of vancomycin added to agar. 

^cND, not done.