TABLE 6.

MICs of selected clones of C. difficile obtained in single-step and multistep resistance development experiments compared to parent strains

C. difficile strain and selecting antibiotic	Selection step, medium	MIC (μg/ml)
		Cadazolid	Linezolid	Moxifloxacin	Fidaxomicin
NCTC 13366 (parent)
None		0.25	2	32	0.25
Cadazolid	Step 1, agar	0.25	2	32	0.25
Cadazolid	Step 2, agar	0.5	2	32	0.25
Cadazolid	Step 3, agar	0.25	2	32	0.25
Linezolid	Step1, agar	0.5	8	32	0.25
Linezolid	Step 2, agar	0.5	8	32	0.25
Linezolid	Step 3, agar	0.5	8	32	0.25
Fidaxomicin	Step 1, agar	0.125	2	32	4
Fidaxomicin	Step 2, agar	0.125	2	32	128
ATCC 9689 (parent)
None		0.25	2	2	≤0.031
Cadazolid	Step 1, agar	0.25	2	2	≤0.03
Cadazolid	Step 2, agar	0.5	4	2	≤0.03
Cadazolid	Step 3, agar	0.5	4	2	≤0.03
Cadazolid	Passage 13, liquid medium	0.25	2	2	≤0.03
Moxifloxacin	Step 1, agar	0.06	2	4	0.008
Moxifloxacin	Step 2, agar	0.125	2	64	0.008
Linezolid	Step 1, agar	0.5	8	2	≤0.03
Linezolid	Step 2, agar	0.5	8	2	≤0.03
Fidaxomicin	Step 1, agar	0.25	4	2	2
Fidaxomicin	Step 2, agar	0.25	4	2	32
Fidaxomicin	Step 3, agar	0.125	4	2	>128
ATCC 700057 (quality control)		0.25	2	2	0.06