Table 3.

Combination index (CIn) values for the equimolar mixture of 2 and 4 in MRSA.^a

Test organism	CIn values
MRSA (ATCC 43300)	2.0
CIMRSA 1	2.0
CIMRSA 2	2.2
CIMRSA 3	1.7
CIMRSA 4	1.6
CIMRSA 5	1.9
CIMRSA 6	2.2
CIMRSA 7	2.3

^aCIn vales were determined by using the following equation: $\mathrm{CIn}=\left(\frac{\left[2\right]}{\left[2\right]x}\right)+\left(\frac{\left[4\right]}{\left[4\right]x}\right)+\left(\frac{\left[2\right]x\left[4\right]}{\left[2\right]x\mathrm{x}\left[4\right]x}\right)$, where [2] and [4] are concentrations of 2 and 4 in combination, inhibiting 50% of cell viability, while [2]_x and [4]_x are the doses of 2 and 4 alone, respectively, inhibiting 50% of cell viability.