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Table 1 Zone diameter intepretive criteria

From: Udder pathogens and their resistance to antimicrobial agents in dairy cows in Estonia

Disc content in μg Staphylococcus spp. Streptococcus spp. Enterococcus spp. Enterobacteriaceae spp.
  S I R S I R S I R S I R
Ampicillin 10 μg ≥ 29 - ≤28 ≥ 26 19-25 ≤18 ≥ 17 - ≤16 ≥ 17 15-16 ≤14
Penicillin 10 μg ≥ 29 - ≥ 29 ≥24 - - ≥15 - ≤14 - - -
Cephalothin 30 μg      - - -    
Cefaperazone 75 μg - - - - - - - - - ≥21 16-20 ≤15
Clindamycin 2 μg ≥ 21 15-20 ≥ 14 ≥19 16-18 ≤15 - - - - - -
Erythromycin 15 μg ≥ 23 14-22 ≥ 14 ≥21 16-20 ≤15 - - - - - -
Gentamycin 10 μg ≥ 12 13-14 ≥ 15 ≥12 13-14 15≤ ≥10 7-9 ≤6 ≥ 12 13-14 ≥ 15
Tetracycline 30 μg ≥ 19 15-18 ≥ 14 ≥23 19-22 ≤18 ≥19 15-18 ≤14 ≥ 19 15-18 ≥ 14
Enrofloxacin 5 μg           ≥ 20 15-19 ≤14
Trimethoprim/sulfa 1,25/23,75 μg ≥ 16 11-15 ≥ 10 ≥16 11-15 ≤10 ≥16 11-15 ≤10 ≥ 16 11-15 ≥ 10
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