TABLE 2.

Resistance incidence of C. difficile BI, BK, K, and QC strains against surotomycin, vancomycin, and rifampin

C. difficile strain	Antibiotic	Concn(s) tested (× MIC)	RIa
			Sample A	Sample B
BI	Surotomycin	8	4.4E−09	<5.4E−09
		16, 32	<4.4E−09	<5.4E−09
	Vancomycin	8, 16, 32	<4.4E−09	<5.4E−09
	Rifampin	8	<4.4E−09	3.2E−08
		16	1.3E−08	5.4E−09
BK	Surotomycin	8	<4.2E−08	<6.0E−08
		16	<4.2E−08	6.0E−08
		32	<4.2E−08	<6.0E−08
	Vancomycin	8, 16, 32	<4.2E−08	<6.0E−08
	Rifampin	8	<4.2E−08	1.2E−07
		16	4.2E−08	<6.0E−08
K	Surotomycin	8, 16, 32	<5.8E−09	<4.9E−09
	Vancomycin	8, 16, 32	<5.8E−09	<4.9E−09
	Rifampin	8	<5.8E−09	9.9E−09
		16	1.7E−08	9.9E−09
QC	Surotomycin	8, 16, 32	<6.5E−09	<5.5E−09
	Vancomycin	8, 16, 32	<6.5E−09	<5.5E−09
	Rifampin	8	1.3E−08	1.1E−08
		16	2.6E−08	5.5E−09

^aRI, resistance incidence. The average numbers of CFU/ml plated for the C. difficile strains were as follows: 1.9E+08 to 2.3E+08 for strain BI, 1.7E+07 to 2.4E+07 for strain BK, 1.7E+08 to 2.0E+08 for strain K, and 1.6E+08 to 1.8E+08 for strain QC.