Methodological comparisons for antimicrobial resistance surveillance in feedlot cattle

BMC Veterinary Research

Table 3 Interpretive criteria for E coli using disk diffusion susceptibility testing reported as inhibition zone diameters (mm)

Antimicrobial	[Disk] (μg)	Susceptible	Intermediate	Resistant	Reference
Ampicillin	10	≥17	14-16	≤13	CLSI M100-S22, 2012
Amoxicillin- Clavulanate	20/10	≥18	14-17	≤13	CLSI M100-S22, 2012
Ceftazidine	30	≥18	15-17	≤14	CLSI M100-S18, 2008
Ceftiofur	30	≥21	18-20	≤17	CLSI M31-A4, 2013
Enrofloxacin	5	≥21	17-20	≤16	*CLSI M31-A4, 2013
Florfenicol	30	≥19	15-18	≤14	*CLSI M31- A4, 2013
Neomycin	30	≥17	-	≤12	*CLSI M31-A3, 2008
Streptomycin	10	≥15	12-14	≤11	CLSI M100-S18, 2008
Sulfisoxazole	300	≥17	13-16	≤12	CLSI M100-S22, 2012
Tetracycline	30	≥15	12-14	≤11	CLSI M31-A4, 2013
Trimethoprim-Sulfamethoxazole	1.25/23.75	≥16	11-15	≤10	CLSI M100-S22, 2012

*Interpretive criteria for M. haemolytica used in lieu of E. coli since CLSI does not define breakpoints for E. coli in cattle for these antimicrobial drugs.
CLSI = Clinical and Laboratory Standards Institute.

ISSN: 1746-6148