Efficacy of Linezolid and Fosfomycin in Catheter-Related Biofilm Infection Caused by Methicillin-Resistant Staphylococcus aureus

Table 1

Minimum inhibitory concentration (MIC) and fractional inhibitory concentration index (FICI) of antibiotics against three methicillin-resistant staphylococcus aureus strains.

Strain	MIC				FICI
	LIN	FOS	LEV	RIF	LIN-FOS	LIN-LEV	LIN-RIF
154311	2 (S)	64 (R)	0.25 (S)	>128 (R)	0.375; (synergism)	0.25; (synergism)	>1; (no interaction or antagonism)
152898	2 (S)	32 (R)	0.25 (S)	>128 (R)	0.5; (synergism)	0.75; (no interaction)	>1; (no interaction or antagonism)
159228	2 (S)	64 (R)	0.25 (S)	>128 (R)	0.375; (synergism)	0.75; (no interaction)	>1; (no interaction or antagonism)

LIN: linezolid; FOS: fosfomycin; LEV: levofloxacin; RIF: rifampin
S: susceptible; R: resistant. MIC was according to CLSI standards: Clinical and Laboratory Standards Institute.
FICI = FIC + FIC = (MIC A/MIC A) + (MIC B/MIC B) = (MIC of drug A in combination/MIC of drug A alone) + (MIC of drug B in combination/MIC of drug B alone).
FICI values were interpreted as follows: synergy, FICI ≤ 0.5; no interaction, 0.5 < FICI ≤ 4.0; antagonism, FICI > 4.0.