TABLE 1.

Breakpoints of the agar dilution and disk diffusion methods used to determine antimicrobial susceptibility of Campylobacter isolates

Antimicrobial agent	Result for method:
	Agar dilution				Disk diffusion
	Test range (μg/ml)	MIC breakpoint (μg/ml)a			Disk concn (μg)	Zone diam breakpoint (mm)b
		S	I	R		S	I	R
Ampicillin	0.06-128	≤8	16	≥32	10	≥17	14-16	≤13
Tetracycline	0.06-128	≤4	8	≥16	30	≥19	15-18	≤14
Gentamicin	0.06-128	≤4	8	≥16	10	≥15	13-14	≤12
Kanamycin	0.25-128	≤16	32	≥64	30	≥18	14-17	≤13
Clindamycin	0.06-128	≤0.5	1-2	≥4	2	≥21	15-20	≤14
Erythromycin	0.06-128	≤0.5	1-4	≥8	15	≥23	14-22	≤13
Ciprofloxacin	0.008-128	≤1	2	≥4	5	≥21	16-20	≤15
Norfloxacin	0.06-128	≤4	8	≥16	10	≥17	13-16	≤12
Nalidixic acid	0.25-128	≤16		≥32	30	≥19	14-18	≤13

^aMIC breakpoints for enteric bacteria from the NARMS were used for all antimicrobial agents except norfloxacin. MIC breakpoints for Enterobacteriaceae for norfloxacin were recommended by the CLSI (formerly NCCLS). S, susceptible; I, intermediate; R, resistant.

^bZone diameter breakpoints of ampicillin, tetracycline, gentamicin, kanamycin, clindamycin, and erythromycin for bacteria isolated from animals were recommended by the CLSI. Zone diameter breakpoints of ciprofloxacin, norfloxacin, and nalidixic acid for Enterobacteriaceae were recommended by the CLSI. S, susceptible; I, intermediate; R, resistant.