Table 1.

Antibacterial activity of RBx 14255 against Clostridium spp. and other anaerobic bacteria

Organism (n) and antimicrobial agent	MIC (μg/ml)
	MIC50	MIC90	Range
C. difficile (28)a
RBx 14255	0.5	4	0.125–8
Telithromycin	0.5	8	0.5–16
Erythromycin	2	16	2–>16
Clarithromycin	1	>16	1–>16
Vancomycin	1	4	0.5–8
Metronidazole	0.25	2	0.06–4
Clindamycin	8	>16	2–>16
Clostridium spp. (11)b
RBx 14255	0.06	0.125	0.03–0.25
Telithromycin	0.125	2	0.5–4
Erythromycin	2	8	2–16
Clarithromycin	0.5	16	0.06–16
Vancomycin	0.5	1	0.5–4
Metronidazole	0.25	1	0.03–1
Clindamycin	0.5	1	0.125–8
Propionibacterium acnes (6)c
RBx 14255	0.03	1	0.015–1
Telithromycin	0.125	4	0.06–>4
Erythromycin	0.125	0.25	0.125–0.25
Clarithromycin	0.125	0.25	0.03–0.5
Vancomycin	1	1	0.125–1
Metronidazole	16	16	16
Clindamycin	0.25	1	0.25–1
B. fragilis (17)d
RBx 14255	2	8	1–16
Telithromycin	2	16	2–16
Erythromycin	8	>16	8–>16
Clarithromycin	8	>16	8–>16
Vancomycin	16	16	16–>16
Metronidazole	0.5	2	0.25–2
Clindamycin	1	16	1–>16
F. nucleatum (3)e
RBx 14255	8	16	8–>16
Telithromycin	2	4	2–16
Erythromycin	>16	>16	>16
Clarithromycin	>16	>16	>16
Vancomycin	16	16	8–>16
Metronidazole	0.25	0.5	0.06–0.5
Clindamycin	0.06	0.125	0.03–0.125

^aClostridium difficile ATCC 43255, C. difficile ATCC 43596, C. difficile ATCC 9689, C. difficile NCTC 11223, C. difficile BI/NAP1/027-2001155, and C. difficile clinical isolates (23).

^bClostridium perfringens ATCC 13124, C. perfringens clinical isolates (4), Clostridium cadaveris 6400, Clostridium bifermentans (3), and Clostridium subterminale (2).

^cPropionibacterium acnes ATCC 6919, P. acnes clinical isolates (5).

^dBacteroides fragilis ATCC 25285, B. fragilis (16).

^eFusobacterium nucleatum 5356, F. nucleatum (2).