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Table 1 Interpretative criteria for E. coli O157:H7 using disk diffusion susceptibility testing reported as inhibition zone diameters (mm)

From: Prevalence of Escherichia coli O157:H7 in beef cattle at slaughter and beef carcasses at retail shops in Ethiopia

Antimicrobial Disk (μg) Susceptible Intermediate Resistant Antimicrobial class WHO classification
Amoxicillin 25 ≥17 14–16 ≤13 β-lactams Critically important
Cefoxitin 5 ≥18 15–17 ≤14 Cephalosporins Critically important
Chloramphenicol 30 ≥18 13–17 ≤12 Phenicols Highly important
Ciprofloxacin 5 ≥31 21–30 ≤20 Quinolones Critically important
Kanamycin 30 ≥18 14–18 ≤13 Aminoglycosides Critically important
Nalidixic acid 30 ≥19 14–18 ≤13 Quinolones Critically important
Nitrofurantoin 300 ≥17 15–16 ≤14 Nitrofurans Important
Streptomycin 10 ≥15 12–14 ≤11 Aminoglycosides Critically important
Trimethoprim-sulfamethoxazole 1.25/23.75 ≥16 11–15 ≤10 Folate pathway inhibitors Highly important
Tetracycline 30 ≥15 12–14 ≤11 Tetracyclines Highly important