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Table 1 Guidelines for antibiotic discs used for antimicrobial susceptibility test of E. coli with their respective concentrations

From: Occurrence and antimicrobial susceptibility profile of Escherichia coli O157:H7 from food of animal origin in Bishoftu town, Central Ethiopia

Antimicrobial agent Symbol Disc content Zone of inhibition in millimeters (mm) with its interpretation
Susceptible Intermediate Resistant
Ceftriaxone CRO 30 μg ≥ 23 20–22 ≤ 19
Streptomycin S 10 μg ≥ 15 12–14 ≤ 11
Tetracycline TTC 30 μg ≥ 15 12–14 ≤ 11
Gentamycin GN 10 μg ≥ 15 13–14 ≤ 12
Ciprofloxacilin CIP 5 μg ≥ 21 16–20 ≤ 15
Vancomycin VA 30 μg ≥ 12 10–11 ≤ 9
Chloramphenicol C 30 μg ≥ 18 13–17 ≤ 12
Ampicillin AMP 10 μg ≥ 14 12–13 ≤ 11
  1. Source: (CLSI (clinical and laboratory standards institute), 2012)