Epigallocatechin Gallate Synergistically Enhances the Activity of Carbapenems against Methicillin-Resistant Staphylococcus aureus

DOI: 10.1128/AAC.46.2.558-560.2002

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FIG. 1.
Synergistic anti-MRSA effects of combinations of IPM and EGCg. (A) Growth inhibition curves. ○, IPM alone; •, IPM plus EGCg at 1.56 μg/ml; ▴, IPM plus EGCg at 3.12 μg/ml; ▾, IPM plus EGCg at 6.25 μg/ml; ⧫, IPM plus EGCg at 12.5 μg/ml; ▪, IPM plus EGCg at 25 μg/ml; OD, optical density. (B) Time-kill curves. ○, no addition; ▵, IPM at 32 μg/ml alone; ▿, EGCg at 25 μg/ml alone; •, IPM at 4 μg/ml plus EGCg at 3.125 μg/ml (1/32 of their MICs); ▴, IPM at 8 μg/ml plus EGCg at 6.25 μg/ml (1/16 of their MICs); ▾, IPM at 16 μg/ml plus EGCg at 12.5 μg/ml (1/8 of their MICs); ▪, IPM at 32 μg/ml plus EGCg at 25 μg/ml (1/4 of their MICs).

TABLE 1.

Effects of carbapenems in combination with EGCg against 24 MRSA isolates

Combination	MIC₅₀ (μg/ml)^a of combination	% of MRSA isolates showing indicated effect:
Combination	MIC₅₀ (μg/ml)^a of combination	Synergistic	Additive	None	MIC of ≤4 μg/ml^b
EGCg 1.56 μg/ml
IPM	64	0	46	54	0
PAPM	32	4	33	63	4
MEM	64	0	42	58	0
EGCg 3.125 μg/ml
IPM	32	42	41	17	8
PAPM	16	29	63	8	21
MEM	32	38	62	0	4
EGCg 6.25 μg/ml
IPM	8	83	17	0	38
PAPM	8	75	17	8	46
MEM	8	83	17	0	25
EGCg 12.5 μg/ml
IPM	8	88	12	0	46
PAPM	2	83	9	8	67
MEM	8	88	12	0	42
EGCg 25 μg/ml
IPM	0.25	92	8	0	75
PAPM	0.5	88	12	0	75
MEM	2	83	17	0	71

↵ a MICs at which 50% of the isolates treated with carbapenem alone are inhibited: IPM, 128 μg/ml; PAPM 32 μg/ml; MEM, 64 μg/ml.
↵ b MIC susceptibility breakpoint is ≤4 μg/ml for IPM and MEM, as determined by NCCLS, but is not available for PAPM at present.