TABLE 1.

In vitro activities of several antimicrobial agents against 1,343 B. fragilis group isolates (1997 to 2006)

Organism (na) and antimicrobial agent	MIC (μg/ml)			% Resistant strainsb
	Range	50%	90%
B. fragilis group (1,343)
Metronidazole	≤0.06-8	1	2	0
Chloramphenicol	0.125-16	4	8	0
Clindamycin	≤0.06->256	2	>256	38.3
Tigecycline	≤0.06-32	1	8	7.4
Moxifloxacin	≤0.06-128	1	8	13.9
Amoxicillin-clavulanate	≤0.06-256	1	8	10.1
Piperacillin-tazobactam	≤0.06-256	2	16	0.8
Cefoxitin	≤0.06-256	16	32	10.8
Imipenem	≤0.06->256	0.25	1	0.4
B. fragilis (833)
Metronidazole	≤0.06-8	1	2	0
Chloramphenicol	0.125-8	4	8	0
Clindamycin	≤0.06->256	2	>256	33.3
Tigecycline	≤0.06-16	1	8	6.5
Moxifloxacin	≤0.06-64	0.5	4	9.7
Amoxicillin-clavulanate	≤0.06-256	1	8	6.2
Piperacillin-tazobactam	≤0.06->256	1	8	0.5
Cefoxitin	≤0.06-256	8	32	6.4
Imipenem	≤0.06->256	0.25	1	0.6
B. thetaiotaomicron (182)
Metronidazole	≤0.06-4	1	2	0
Chloramphenicol	0.125-8	4	8	0
Clindamycin	≤0.06->256	4	>256	47.3
Tigecycline	≤0.06-16	1	8	7.5
Moxifloxacin	≤0.06-64	2	16	17
Amoxicillin-clavulanate	0.125-64	2	16	4.9
Piperacillin-tazobactam	≤0.06->256	16	32	3.3
Cefoxitin	≤0.06-256	32	64	23.6
Imipenem	≤0.06-32	0.5	2	0.5
B. uniformis (106)
Metronidazole	0.125-4	1	2	0
Chloramphenicol	1-8	4	8	0
Clindamycin	≤0.06->256	2	>256	40.6
Tigecycline	≤0.06-16	1	8	9.1
Moxifloxacin	≤0.06-128	2	32	24.5
Amoxicillin-clavulanate	0.25-64	1	16	12.3
Piperacillin-tazobactam	≤0.06-32	4	16	0
Cefoxitin	≤0.06-128	16	32	9.4
Imipenem	≤0.06-4	0.25	2	0
B. vulgatus (47)
Metronidazole	0.25-4	1	2	0
Chloramphenicol	1-8	4	8	0
Clindamycin	≤0.06->256	4	>256	44.7
Tigecycline	0.125-16	0.5	8	6.1
Moxifloxacin	0.5-64	2	16	17
Amoxicillin-clavulanate	0.25-32	2	16	21.3
Piperacillin-tazobactam	≤0.06-64	8	32	0
Cefoxitin	1-256	16	64	17
Imipenem	≤0.06-4	0.5	2	0
B. caccae (45)
Metronidazole	0.125-8	1	2	0
Chloramphenicol	1-8	4	8	0
Clindamycin	≤0.06->256	4	>256	46.7
Tigecycline	0.125-64	1	16	16.1
Moxifloxacin	0.25-64	2	32	22.2
Amoxicillin-clavulanate	0.125-32	2	16	20
Piperacillin-tazobactam	≤0.06-128	8	32	2.2
Cefoxitin	≤0.06-64	16	32	8.9
Imipenem	≤0.06-4	0.5	2	0
B. distasonis (43)
Metronidazole	0.5-4	1	2	0
Chloramphenicol	1-16	8	8	0
Clindamycin	≤0.06->256	4	>256	41.9
Tigecycline	0.125-32	2	8	8.3
Moxifloxacin	≤0.06-128	1	16	18.6
Amoxicillin-clavulanate	0.125-64	4	16	16.3
Piperacillin-tazobactam	≤0.06-32	16	16	0
Cefoxitin	≤0.06-128	32	64	25.6
Imipenem	≤0.06-4	1	1	0
B. ovatus (41)
Metronidazole	0.125-4	1	2	0
Chloramphenicol	0.25-8	4	8	0
Clindamycin	≤0.06->256	4	>256	48.8
Tigecycline	0.125-16	2	8	7.2
Moxifloxacin	0.125-32	2	32	24.4
Amoxicillin-clavulanate	0.125-32	1	16	17.1
Piperacillin-tazobactam	≤0.06-32	8	16	0
Cefoxitin	0.5-128	16	64	12.2
Imipenem	≤0.06-8	0.25	2	0
Other B. fragilis group species (46)c
Metronidazole	0.125-4	0.5	2	0
Chloramphenicol	2-16	4	8	0
Clindamycin	≤0.06->256	4	>256	45.7
Tigecycline	0.125-16	1	8	10.5
Moxifloxacin	0.25-128	2	16	28.3
Amoxicillin-clavulanate	0.25-64	2	16	19.6
Piperacillin-tazobactam	≤0.06-32	8	32	0
Cefoxitin	2-128	16	64	23.9
Imipenem	≤0.06-4	0.25	2	0

^an, no. of isolates.

^bMICs for resistant isolates are those described by CLSI. The breakpoint for tigecycline is that recommended by the FDA.

^cBacteroides spp., 24 isolates; B. eggerthii, 8 isolates; B. merdae, 7 isolates; and B. stercoris, 7 isolates.