TABLE 1.

In vitro activities of 12 antimicrobial agents against 139 B. pilosicoli isolates

Antimicrobial agent	No. of isolates inhibited at MIC (μg/ml) of:																	MIC50	MIC90	% Susa
	≤0.016	0.03	0.06	0.125	0.25	0.5	1	2	4	8	16	32	64	128	256	512	>512
Amoxicillin					4	26	34	5	7	5	24	18	12	4				4	64	54.7
Amoxicillin-clavulanic acidb					4	35	39	35	26									1, 0.5	4, 2	100
Ceftriaxone				19	85	23	11	1										0.25	1	100
Chloramphenicol						4	95	40										1	2	100
Ciprofloxacin							4	51	84									4	4	39.6
Clindamycin	3	0	8	13	21	32	23	14	6	8	10	1						0.5	8	86.3
Erythromycin									1	0	1	8	2	32	66	0	29	256	>512	NA
Gentamicin						3	4	14	48	55	13	2						4	16	NA
Meropenem				16	115	8												0.25	0.25	100
Metronidazole				19	110	10												0.25	0.25	100
Moxifloxacin							4	113	2									2	2	NA
Tetracycline				66	47	0	10	9	7									0.25	2	100

^aSus, susceptible. The following breakpoints for resistance were used: for amoxicillin, ≥8 μg/ml; for amoxicillin-clavulanic acid, ≥16 and 8 μg/ml, respectively; for ceftriaxone, ≥64 μg/ml; for chloramphenicol, ≥32 μg/ml; for clindamycin, ≥8 μg/ml; for meropenem, ≥16 μg/ml; for metronidazole, ≥32 μg/ml; and for tetracycline, ≥16 μg/ml (17). A breakpoint of ≥4 μg/ml was used for ciprofloxacin (18). NA, not available.

^bSeparate MIC₅₀s and MIC₉₀s are given for amoxicillin and clavulanic acid.