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Table 2 Interpretive criteria for M haemolytica 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 ≤0.5 - - CLSI M45-A2, 2010
Amoxicillin-Clavulanate ≤0.5/0.25 - - CLSI M45-A2, 2010
Cefoxitin ≤8 16 ≥32 *CLSI M100-S22, 2012
Ceftiofur ≤2 4 ≥8 CSLI 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 ≤2 4 ≥8 CLSI M31-A4, 2013
Trimethoprim-Sulfamethoxazole ≤0.5/9.5 - - CLSI M45-A2, 2010
  1. *Interpretive criteria for E. coli used in lieu of M. haemolytica since CLSI does not define breakpoints for M. haemolytica and these antimicrobial drugs.
  2. CLSI = Clinical and Laboratory Standards Institute.