TABLE 2.

Checkerboard assay results for potentially synergistic and antagonistic agents^a

Reference	Agent	MIC (μM)	MIC (μg/mL)	∑FICminb	∑FICmaxc
Table 1; Fig. 1	Cloxacillin	35	15	0.21	1
	Cefotaxime	71	32	0.30	1
	Oxacillin	71	28	0.30	1
	Flucloxacillin	2.2	1.0	0.30	1
	Dicloxacillin	2.2	1.0	0.38	1
	Nafcillin	71	29	0.43	1
	Vancomycin	0.78	1.1	0.60	1
	Balofloxacin	0.02	6.7E–3	0.75	1
	Floxuridine	0.024	5.9E–3	0.75	1
	Rifaximin	0.049	3.9E–2	0.80	1
	Daptomycin	0.28	0.45	0.83	1.1
	Gemcitabine	0.024	6.3E–3	0.96	1.1
	Tetracycline	8.8	3.9	1	1.2
	Doxycycline	0.28	0.12	1	1.2
	Moxifloxacin	0.14	5.6E–2	1	1.2
	Sitafloxacin	0.035	1.4E–2	1	1.2
	Gatifloxacin	0.39	0.15	1	1.4
	Rifabutin	0.086	7.3E–2	1	1.4
	Mupirocin	0.78	0.39	1	2.7
Fig. 2	Imipenem	17	5.3	0.26	1
	Meropenem	31	12	0.38	1
	Ceftaroline fosamil	8.8	6.6	1	1.2
	Cefoxitin sodium	55	25	0.48	1
	Tazobactam	500	150	0.385	1
	Piperacillin Sodium	35	19	0.43	1
	Tazobactam/piperacillin (1:1 wt:wt)	58:32	18:18	0.50	1
Fig. 2e	Cloxacillin	0.54	0.23d	0.50	1

^aThe upper section lists agents identified in Table 1 and several additional β-lactamase-resistant β-lactams (Fig. 1) against MRSA (ATCC 43300). The middle section lists additional follow-up agents (Fig. 2) against MRSA. The bottom row shows the results of a test of the best MRSA synergistic agent (cloxacillin) against an MSSA strain (ATCC 25923) (Fig. 2e). The MIC for ceftobiprole was 2 μg mL⁻¹.

^bLower ∑FIC_min values indicate greater degrees of synergy, with values closer to 1 indicative of agent additivity (no synergy).

^cHigher ∑FIC_max values indicate greater degrees of antagonism, with values closer to 1 indicative of additivity (no antagonism).

^dMIC versus ceftobiprole = 0.25 μg mL⁻¹.