TABLE 3.

The best synergistic concentrations of Rifampin-Melittin based on MIC against selected isolates.

MRSE 1 and 4a		ATCC 35984		MSSE 1		MRSE 8
Rif + Mel (μ g/ml)	FIC indices	Rif + Mel (μg/ml)	FIC indices	Rif + Mel μg/ml	FIC indices	Rif + Mel (μg/ml)	FIC indices
122b + 0.625	0.61	0.0078 + 1.25	2.5	0.0312c + 0.312	0.74	0.0312c + 1.25	0.74
124 + 0.312	0.37	0.0078 + 0.625	2.25	0.0312 + 0.156	0.62	0.0312 + 0.625	0.49
126 + 0.156	0.24	0.0078 + 0.312	2.12	0.0312 + 0.078	0.55	0.0312 + 0.312	0.37
128 + 0.009	0.13	0.0078 + 0.156	2.06	0.0312 + 0.039	0.53	0.0312 + 0.156	0.31
128 + 0.004	0.12	0.0078 + 0.078	2.02	0.0312 + 0.019	0.51	0.0625 + 0.625	0.75
−	−	0.0078 + 0.039	2.01	0.0312 + 0.009	0.5	0.0625 + 0.312	0.62
−	−	0.0078 + 0.019	2	0.0312 + 0.004	0.502	0.0625 + 0.156	0.56
−	−	0.0078 + 0.009	2	−	−	0.0625 + 0.078	0.52
−	−	0.0078 + 0.004	2	−	−	0.0625 + 0.039	0.51
−	−	0.0039 + 1.25	1.5	−	−	0.0625 + 0.019	0.5
−	−		−	−	−	0.0625 + 0.009	0.5
−	−	−	−	−	−	0.0625 + 0.004	0.5

FIC, fractional inhibitory concentration; MRSE, methicillin-resistant S. epidermidis; ATCC, American type culture collection; MSSE, methicillin-susceptible S. epidermidis; Rif, rifampin; Mel, melittin; FIC, fractional inhibitory concentration. ^aThese isolates had the same MIC and MBC results, that way, the same synergism formulation was used, and surprisingly, the same results were found again. ^bThe conventional serial dilution for the antibacterial agent interaction assessment has wide intervals for choosing the concentrations needed to enter the antibacterial agents’ interaction, that way, we selected and used novel concentrations other than conventional serial dilutions. ^cIt should be noted various synergism formulations were used for the survey of antibacterial agents’ interaction because of different MIC results for various selected isolates.