TABLE 4.

Dual-combination 24-h time-kill synergy results for 0.5× MIC^a

Drug at 0.0625× MIC	Change in log10 CFU/mL of strain
	Penicillin susceptible				Penicillin elevated
	JH2-2 (ampicillin MIC of 2 mcg/mL; penicillin MIC of 2 mcg/mL)		L2052 (ampicillin MIC of 0.5 mcg/mL; penicillin MIC of 2 mcg/mL)		L2068 (ampicillin MIC of 1 mcg/mL; penicillin MIC of 8 mcg/mL)		LS4828 (ampicillin MIC of 8 mcg/mL; penicillin MIC of 8 mcg/mL)
	Ceftriaxone	Ceftaroline	Ceftriaxone	Ceftaroline	Ceftriaxone	Ceftaroline	Ceftriaxone	Ceftaroline
Penicillin	−0.93	−3.04	−0.49	−0.17	−1.65	0.19	−0.49	0.10
Ampicillin	−4.21	−4.51	−0.24	−0.88	−0.56	−0.04	−0.04	−0.35
Piperacillin-tazobactam	−2.14	−0.78	−1.14	0.23	0.20	−0.44	−0.12	−0.44
Ertapenem	−3.26	−3.25	0.30	0.53	−3.31	−0.78	−0.10	−0.31
Imipenem-cilastatin	−1.84	−0.42	−0.26	0.26	−2.47	−1.35	−0.07	−0.40
Meropenem	−3.63	−4.20	−0.78	−0.15	−3.56	−0.83	−0.22	−0.43

^aShown are additional decreases in the log₁₀ CFU/mL of the combination compared to its most active single agent at 24 h. Synergy was defined as a ≥2-log₁₀ CFU/mL decrease of the combination compared to tits most active single agent (dark shading). Indifference was defined as a 1- to 2-log₁₀ CFU/mL decrease of the combination compared to its most active single agent (light shading).