TABLE 1.

MICs for the six Clostridium difficile test strains

Antibiotic	MIC (μg/ml) for strain:a
	1	2	3	4	5	6
Ciprofloxacin	16	128	128	128	>256	32
Levofloxacin	8	256	256	>256	>256	8
Gatifloxacin	<2	32	64	32	256	4
Moxifloxacin	<2	32	64	64	256	2
Ceftriaxone	32	64	32	32	16	32
Clindamycin	>256	>256	>256	>256	2	2

^aMICs were determined by broth dilution. Strains 3, 4, and 5 were epidemic strains. The resistance breakpoints (μg/ml) based on Clinical and Laboratory Standards Institute interpretive categories for resistance were 8 for each of the fluoroquinolones, 64 for ceftriaxone, and 8 for clindamycin.