Table 3.

In vitro frequency of resistance by C. difficile against RBx 14255 and other standard drugs

C. difficile strain/drug	Frequency of spontaneous resistance
	4× MIC (mg/liter)	16× MIC (mg/liter)
ATCC 43255
RBx 14255	2 × 10−8	<7.0 × 10−9
Vancomycin	3.5 × 10−9	<7.0 × 10−9
Metronidazole	2.0 × 10−9	6.0 × 10−9
Rifampin	1.0 × 10−7	3.5 × 10−7
6387
RBx 14255	1.5 × 10−9	4.0 × 10−9
Vancomycin	4.5 × 10−9	<6.5 × 10−9
Metronidazole	1.0 × 10−8	<6.5 × 10−9
Rifampin	1.5 × 10−7	2.0 × 10−7