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Table 1 Interpretive criteria for E coli using broth microdilution susceptibility testing reported as minimum inhibitory concentrations (μg/ml)

From: Methodological comparisons for antimicrobial resistance surveillance in feedlot cattle

Antimicrobial

Susceptible

Intermediate

Resistant

Reference

Amikacin

≤16

32

≥64

CLSI M100-S22, 2012

Ampicillin

≤8

16

≥32

CLSI M100-S22, 2012

Amoxicillin-Clavulanate

≤8/4

16/8

≥32/16

CLSI M100-S22, 2012

Cefoxitin

≤8

16

≥32

CLSI M100-S22, 2012

Ceftiofur

≤2

4

≥8

CLSI M31-A4, 2013

Ceftriaxone

≤1

2

≥4

CLSI M100-S22, 2012

Chloramphenicol

≤8

16

≥32

CLSI M100-S22, 2012

Ciprofloxacin

≤1

2

≥4

CLSI M100-S21, 2011

Gentamicin

≤4

8

≥16

CLSI M100-S22, 2012

Kanamycin

≤16

32

≥64

CLSI M100-S22, 2012

Nalidixic Acid

≤16

-

≥32

CLSI M100-S22, 2012

Streptomycin

≤32

-

≥64

NARMS Executive Report 2009

Sulfisoxazole

≤256

-

≥512

CLSI M100-S22, 2012

Tetracycline

≤4

8

≥16

CLSI M100-S22, 2012

Trimethoprim-Sulfamethoxazole

≤2/38

-

≥4/76

CLSI M100-S22, 2012

  1. CLSI = Clinical and Laboratory Standards Institute.