TABLE 6.

Comparison of reports on MICs for B. anthracis

Antibiotic	Source or reference	Test method	No. of strains	MIC (μg/ml)			Breakpointsa		Interpretation (%)b
				Range	50%	90%	S (≤)	R (≥)	Se	I	R
Amoxycillin-clavulanic	This study	Etest	45	0.016-0.5	0.032	0.047	4	8	100
acid	This study	Agar dilution	10	0.015-0.06	0.03	0.06			100
	4	Agar dilution	96	0.125-16	0.125	4			88.5		11.5
	10	Agar dilution	22	0.015-0.015	0.015	0.015			100
	22	Agar dilution	70	0.03-64	0.125	0.06			99		1
Azithromycin	This study	Etest	73	1-12	3	6	2	8	26	64	10
Cefotaxime	This study	Etest	76	3->32	>32	>32	8	64	1		99c
	This study	Agar dilution	10	16-64	32	32				100
	10	Disk diffusion	22						4	14	82
	10	Agar dilution	22	8-32	32	32
	29	Disk diffusion	44							100
Ciprofloxacin	This study	Etest	76	0.032-0.094	0.064	0.094	≤0.5		100
	This study	Agar dilution	10	0.06	0.06	0.06			100
	4	Agar dilution	96	0.03-0.5	0.06	0.25			100
	9	Etest	25	0.032-0.38	0.094	0.094			100
	10	Agar dilution	22	0.03-0.06	0.03	0.06			100
	10	Disk diffusion	22						100
	12	Agar dilution	40	<0.008-0.12	0.03	0.06			100
	Klugman et al.f	NCCLS methods	25	0.0625-0.125	0.0625	0.0625			100
	22	Agar dilution	70	0.03-0.06	0.06	0.06			100
	26	Agar dilution	65	0.03-0.12	0.06	0.06			100
	Brooks et al.d	Microdilution	12	<0.25	<0.25	<0.25			100
Erythromycin	This study	Etest	69	0.5-4	1	1.5	0.5	8	15	85
	This study	Agar dilution	10	0.5-2	1	2			10	90
	4	Agar dilution	96	0.5-4	1	1			95.4	4.6
	10	Disk diffusion	22						100
	Klugman et al.	NCCLS methods	25	0.125-4	0.5	1			NA
	22	Agar dilution	70	0.25-1	0.5	1			NA	NA	0
	26	Agar dilution	65	0.5-1	1	1			3	97
	29	Disk diffusion	44						100
	Brooks et al.	Microdilution	12	0.25-4	0.5	1			8	92
Gentamicin	This study	Etest	75	0.064-0.5	0.25	0.38	4	16	100
	This study	Agar dilution	10	0.25-0.5	0.25	0.5			100
	4	Agar dilution	96	0.125-0.5	0.25	0.5			100
	10	Agar dilution	22	0.03-0.25	0.06	0.125			100
	10	Disk diffusion	22						100
	22	Agar dilution	70	0.06-0.5	0.125	0.25			100
	29	Disk diffusion	44						97.8	2.2
Penicillin	This study	Etest	74	<0.016->32	<0.016	0.023	0.12	0.25	97		3
	This study	Agar dilution	8	0.015-0.5	0.015	0.015			—e
	4	Agar dilution	96	0.125-16	0.125	8			88.5		11.5
	9	Etest	25	<0.016-0.5	0.042	0.236			88		12
	10	Agar dilution	22	0.015-0.03	0.015	0.015			100
	10	Disk diffusion	22						100
	12	Agar dilution	40	0.016-0.03	0.016	0.016			100
	22	Agar dilution	70	0.015-64	0.06	0.125			99		1
	26	Agar dilution	65	<0.06-128	≤0.06	≤0.06			97		3
	29	Disk diffusion	44						84.1	15.9
Tetracycline	This study	Etest	71	0.016-0.094	0.023	0.032	1		100
	This study	Agar dilution	10	0.015-0.06	0.015	0.03			100
	10	Disk diffusion	22						100
	22	Agar dilution	70	0.6-1	0.125	0.125			100
	26	Agar dilution	65	0.03-0.06	0.03	0.06			100
	29	Disk diffusion	44						100
Vancomycin	This study	Etest	74	0.75-5	2	3	4	32	99	1
	This study	Agar dilution	10	1-4	4	4			100
	4	Agar dilution	96	0.25-2	1	1			100
	10	Agar dilution	22	0.25-1	1	1			95	5
	10	Disk diffusion	22						95	5
	26	Agar dilution	65	0.5-2	2	2			100

^aNCCLS MIC interpretive standards (see footnotes to Table 3). Interpretations in the cited reports predate the newly available NCCLS breakpoints for B. anthracis and ciprofloxacin, penicillin, and tetracycline.

^bS, susceptible; I, intermediate; R, resistant; NA, information not available.

^cResistance inferred. The highest level on the strips used was 32 μg/ml.

^dT. Brooks, P. C. B. Turnbull, and A. Maule, unpublished results.

^e—, for penicillin, ASC 32, ASC 70, and ASC 183 resistant; remainder susceptible.

^fK.P. Klugman, J. Frean, L. Arntzen, V. Yeldandi, and S. Bukofzer, Addendum, Abstr. 41st Intersci. Conf. Antimicrob. Agents Chemother., abstr. UL-20, p. 7, 2001.