| Antimicrobial Agents / Microorganisms | Disk Code | Disk Potency (µg) | Resistant | Intermediate | Susceptible |
| Amikacin Enterobacteriaceae, P. aeruginosa Acinetobacter spp, Staphylococcus spp | AK | 30 | ≤14 | 15-16 | ≥17 |
| Amoxycillin-Clavulanic acid Enterobacteriaceae Staphylococcus spp Haemophilus spp | AMC | 20/10 | ≤13 ≤19 ≤19 | 14-17 — — | ≥18 ≥20 ≥20 |
| Ampicillin Enterobacteriaceae and Vibrio cholerae Staphylococcus spp Enterococcus spp Haemophilus spp Streptococcus spp. β-haemolytic Group | AMP | 10 | ≤13 ≤28 ≤16 ≤18 — | 14-16 — — 19-21 — | ≥17 ≥29 ≥17 ≥22 ≥24 |
| Ampicillin-Sulbactam Enterobacteriaceae, Acinetobacter spp., & Staphylococcus spp. Haemophilus spp. | SAM | 10/10 | ≤11 ≤19 | 12-14 — | ≥15 ≥20 |
| Azithromycin Staphylococcus spp., Streptococcus spp Viridans Group, β-haemolytic Group, and S. pneumoniae Neisseria meningitidis Haemophilus spp. | AZM | 15 | ≤13 — — | 14-17 — — | ≥18 ≥20 ≥12 |
| Aztreonam Enterobacteriaceae Pseudomonas aeruginosa Haemophilus spp. | ATM | 30 | ≤17 ≤15 — | 18-20 16-21 — | ≤21 ≥22 26 |
| Carbenicillin Enterobacteriaceae Pseudomonas aeruginosa | CAR | 100 | ≤19 ≤13 | 20-22 14-16 | ≥23 ≥17 |
| Cefaclor Enterobacteriaceae & Staphylococcus spp. Haemophilus spp. | CEC | 30 | ≤14 ≤16 | 15-17 17-19 | ≥18 ≥20 |
| Cefamandole Enterobacteriaceae & Staphylococcus spp. | MA | 30 | ≤14 | 15-17 | ≥18 |
| Cefazolin Staphylococcus spp. | KZ | 30 | ≤14 | 15-17 | ≥18 |
| Cefepime Enterobacteriaceae, P. aeruginosa, Acinetobacter spp. & Staphylococcus spp. Haemophilus spp. Neisseria gonorrhoeae Streptococcus spp. Β haemolytic group Streptococcus spp. Viridans group | FEP | 30 | ≤14 — — — ≤21 | 15-17 — — — 22-23 | ≥18 ≥26 ≥31 ≥24 ≥24 |
| Cefixime Enterobacteriaceae Haemophilus spp. Neisseria gonorrhoeae | CFM | 5 | ≤15 — — | 16-18 — — | ≥19 ≥21 ≥31 |
| Cefonicid Enterobacteriaceae & Staphylococcus spp. Haemophilus spp. | CID | 30 | ≤14 ≤16 | 15-17 17-19 | ≥18 ≥20 |
| Cefoperazone Enterobacteriaceae, P. aeruginosa & Staphylococcus spp. | CFP | 75 | ≤15 | 16-20 | ≥21 |
| Cefotaxime Enterobacteriaceae P. aeruginosa, Acinetobacter spp., & Staphylococcus spp. Haemophilus spp. Neisseria meningitidis Neisseria gonorrhoeae Streptococcus spp.Β haemolytic group Streptococcus spp. Viridans group | CTX | 30 | ≤22 ≤14 — — — — ≤25 | 23-25 15-22 — — — — 26-27 | ≥26 ≥23 ≥26 ≥34 ≥31 ≥24 ≥28 |
| Cefotetan Enterobacteriaceae & Staphylococcus spp. Neisseria gonorrhoeae | CTT | 30 | ≤12 ≤19 | 13-15 20-25 | ≥16 ≥26 |
| Cefoxitin Enterobacteriaceae S. aureus & S. lugdunensis Coagulase-negative Staphylococci Neisseria gonorrhoeae | FOX | 30 | ≤14 ≤21 ≤24 ≤23 | 15-17 — — 24-27 | ≥18 ≥22 ≥25 ≥28 |
| Cefpodoxime Enterobacteriaceae & Staphylococcus spp. Haemophilus spp. Neisseria gonorrhoeae | CPD | 10 | ≤17 — — | 18-20 — — | ≥21 ≥21 ≥29 |
| Cefprozil Enterobacteriaceae, Staphylococcus spp., & Haemophilus spp. | CPR | 30 | ≤14 | 15-17 | ≥18 |
| Ceftazidime Enterobacteriaceae P. aeruginosa, Acinetobacter spp., & Staphylococcus spp. B. cepacia Haemophilus spp. Neisseria gonorrhoeae | CAZ | 30 | ≤17 ≤14 ≤17 — — | 18-20 15-17 18-20 — — | ≥21 ≥18 ≥21 ≥26 ≥31 |
| Ceftizoxime Enterobacteriaceae P. aeruginosa & Staphylococcus spp. Haemophilus spp. Neisseria gonorrhoeae | ZOX | 30 | ≤21 ≤14 — — | 22-24 15-19 — — | ≥25 ≥20 ≥26 ≥38 |
| Ceftriaxone Enterobacteriaceae P. aeruginosa, Acinetobacter spp., & Staphylococcus spp. Haemophilus spp. Neisseria meningitidis Neisseria gonorrhoeae Streptococcus spp. Β haemolytic group Streptococcus spp. Viridans group | CRO | 30 | ≤19 ≤13 — — — — ≤24 | 20-22 14-20 — — — — 25-26 | ≥23 ≥21 ≥26 ≥34 ≥35 ≥24 ≥27 |
| Cefuroxime (parenteral) Enterobacteriaceae & Staphylococcus spp. Haemophilus spp. Neisseria gonorrhoeae | CXM | 30 | ≤14 ≤16 ≤25 | 15-17 17-19 26-30 | ≥18 ≥20 ≥31 |
| Cephalothin Enterobacteriaceae & Staphylococcus spp. | KF | 30 | ≤14 | 15-17 | ≥18 |
| Chloramphenicol Enterobacteriaceae, staphylococcus spp. Enterococcus spp., & Vibrio cholera Haemophilus spp. Neisseria meningitidis Streptococcus pneumoniae Streptococcus spp. Viridans group & β-haemolytic group | C | 30 | ≤12 ≤25 ≤19 ≤20 ≤17 | 13-17 26-28 20-25 — 18-20 | ≥18 ≥29 ≥26 ≥21 ≥21 |
| Ciprofloxacin Enterobacteriaceae, P. aeruginosa, Acinetobacter spp., Staphylococcus spp., & Enterococcus spp. Haemophilus spp. Neisseria meningitidis Neisseria gonorrhoeae | CIP | 5 | ≤15 — ≤32 ≤27 | 16-20 — 33-34 28-40 | ≥21 ≥21 ≥35 ≥41 |
| Clarithromycin Staphylococcus spp. Haemophilus spp. Streptococcus spp. Viridans group, β-haemolytic group & S. pneumoniae | CLR | 15 | ≤13 ≤10 ≤16 | 14-17 11-12 17-20 | ≥18 ≥13 ≥21 |
| Clindamycin Staphylococcus spp. Streptococcus spp. Viridans group, β-haemolytic group & S. pneumoniae | DA | 2 | ≤14 ≤15 | 15-20 16-18 | ≥21 ≥19 |
| Colistin Pseudomonas aeruginosa | CT | 10 | ≤10 | — | ≥11 |
| Doripenem | DOR | 10 | — | — | — |
| Doxycycline Enterobacteriaceae Acinetobacter spp. Staphylococcus spp. & Enterococcus spp. | DO | 30 | ≤10 ≤9 ≤12 | 11-13 10-12 13-15 | ≥14 ≥13 ≥16 |
| Ertapenem Enterobacteriaceae & Staphylococcus spp. Haemophilus spp. | ETP | 10 | ≤15 — | 16-18 — | ≥19 ≥19 |
| Erythromycin Staphylococcus spp. & Enterococcus spp. Streptococcus spp. Viridans group, β-haemolytic group & S. pneumoniae | E | 15 | ≤13 ≤15 | 14-22 16-20 | ≥23 ≥21 |
| Gentamicin Enterobacteriaceae, P. aeruginosa, Acinetobacter Spp., and Staphylococcus spp. | CN | 10 | ≤12 | 13-14 | ≥15 |
| Imipenem Enterobacteriaceae, P. aeruginosa, Acinetobacter Spp., & Staphylococcus spp. Haemophilus spp. | IPM | 10 | ≤13 — | 14-15 — | ≥16 ≥16 |
| Kanamycin Enterobacteriaceae & Staphylococcus spp. | K | 30 | ≤13 | 14-17 | ≥18 |
| Levofloxacin Enterobacteriaceae, P. aeruginosa, S. maltophila, Acinetobacter spp., Enterococcus spp., Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae Staphylococcus spp. Haemophilus spp. | LEV | 5 | ≤13 ≤15 — | 14-16 16-18 — | ≥17 ≥19 ≥17 |
| Linezolid Staphylococcus spp. Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae Enterococcus spp. | LZD | 30 | ≤20 — ≤20 | — — 21-22 | ≥21 ≥21 ≥23 |
| Lomefloxacin Enterobacteriaceae, P. aeruginosa & Staphylococcus spp. Haemophilus spp. Nesseria gonorrhoeae | LOM | 10 | ≤18 — ≤26 | 19-21 — 23-37 | ≥22 ≥22 ≥38 |
| Mecillinam Enterobacteriaceae | MEL | 10 | ≤11 | 12-14 | ≥15 |
| Meropenem Enterobacteriaceae, P. aeruginosa, Acinetobacter Spp., & Staphylococcus spp. B. cepacia Neisseria meningitidis Haemophilus spp. | MEM | 10 | ≤13 ≤15 — — | 14-15 16-19 — — | ≥16 ≥20 ≥30 ≥20 |
| Meziocillin Enterobacteriaceae & Acinetobacter spp. Pseudomonas aeruginosa | MEZ | 75 | ≤17 ≤15 | 18-20 — | ≥21 ≥16 |
| Minocycline Enterobacteriaceae, P. aeruginosa & Acinetobacter spp. Neisseria meningitidis S. maltophila, B. cepacia, Staphylococcus spp., & Enterococcus spp. | MH | 30 | ≤12 — ≤14 | 13-15 — 15-18 | ≥16 ≥26 ≥19 |
| Moxifloxacin Staphylococcus spp. Streptococcus pneumoniae Haemophilus spp. | MFX | 5 | ≤20 ≤14 — | 21-23 15-17 — | ≥24 ≥18 ≥18 |
| Nafcillin Staphylococcus aureus | NF | 1 | ≤10 | 11-12 | ≥13 |
| Nalidixic acid Enterobacteriaceae Neisseria meningitidis | NA | 30 | ≤13 ≤25 | 14-18 — | ≥19 ≥26 |
| Netilmicin Enterobacteriaceae, P. aeruginosa, & Staphylococcus spp. | NET | 30 | ≤12 | 13-14 | ≥15 |
| Nitrofurantoin Enterobacteriaceae, Staphylococcus spp., Enterococcus spp. | F | 300 | ≤14 | 15-16 | ≥17 |
| Norfloxacin Enterobacteriaceae, P. aeruginosa, Staphylococcus spp., & Enterococcus spp. | NOR | 10 | ≤12 | 13-16 | ≥17 |
| Ofloxacin Enterobacteriaceae, P. aeruginosa, & Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae Staphylococcus spp. Haemophilus spp. Neisseria gonorrhoeae | OFX | 5 | ≤12 ≤14 — ≤24 | 13-15 15-17 — 25-30 | ≥16 ≥18 ≥16 ≥31 |
| Oxacillin S. aureus S. pneumoniae (for penicillin susceptibility) | OX | 1 | ≤10 — | 11-12 — | ≥13 ≥20 |
| Penicillin Staphylococcus spp. Enterococcus spp. Neisseria gonorrhoeae Streptococcus spp. β-haemolytic group | P | 10 | ≤28 ≤14 ≤26 — | — — 27-46 — | ≥29 ≥15 ≥47 ≥24 |
| Piperacillin Enterobacteriaceae & Acinetobacter spp. Pseudomonas aeruginosa | PRL | 100 | ≤17 ≤17 | 18-20 — | ≥21 ≥18 |
| Piperacillin-Tazobactam Enterobacteriaceae & Acinetobacter spp. Pseudomonas aeruginosa Staphylococcus spp. Haemophilus spp. | TZP | 100/10 | ≤17 ≤17 ≤17 — | 18-20 — — — | ≥21 ≥18 ≥18 ≥21 |
| Polymyxin B Pseudomonas aeruginosa | PB | 300 | ≤11 | — | ≥12 |
| Quinupristin-Dalfopristin Staphylococcus spp., Enterococcus spp., & Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae | QD | 15 | ≤15 | 16-18 | ≥19 |
| Rifampin Staphylococcus spp., Enterococcus spp., & Haemophilus spp. Neisseria meningitidis Streptococcus pneumoniae | RD | 5 | ≤16 ≤19 ≤16 | 17-19 20-24 17-18 | ≥20 ≥25 ≥19 |
| Spectinomycin Neisseria gonorrhoeae | SH | 100 | ≤14 | 15-17 | ≥18 |
| Streptomycin Enterobacteriaceae | S | 10 | ≤11 | 12-14 | ≥15 |
| Sulfisoxazole Enterobacteriaceae, Staphylococcus spp. & Vibrio cholera | SFX | 300 | ≤12 | 13-16 | ≥17 |
| Telithromycin Staphylococcus spp. Haemophilus spp. Streptococcus pneumoniae | TEL | 15 | ≤18 ≤11 ≤15 | 19-21 12-14 16-18 | ≥22 ≥15 ≥19 |
| Tetracycline Enterobacteriaceae & Acinetobacter spp. Staphylococcus spp. Enterococcus spp., & Vibrio cholera Haemophilus spp. Neisseria gonorrhoeae Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae | TE | 30 | ≤11 ≤14 ≤25 ≤30 ≤18 | 12-14 15-18 26-28 31-37 19-22 | ≥15 ≥19 ≥29 ≥38 ≥23 |
| Ticarcillin Enterobacteriaceae & Acinetobacter spp. Pseudomonas aeruginosa | TIC | 75 | ≤14 ≤14 | 15-19 — | ≥20 ≥15 |
| Ticarcillin-Clavulanic Acid Enterobacteriaceae & Acinetobacter spp. Pseudomonas aeruginosa Staphylococcus spp. | TIM | 75/10 | ≤14 ≤14 ≤22 | 15-19 — — | ≥20 ≥15 ≥23 |
| Tigecyline | TGC | 15 | — | — | — |
| Tobramycin Enterobacteriaceae & P. aeruginosa Acinetobacter spp. & Staphylococcus spp. | TOB | 10 | ≤12 | 13-14 | ≥15 |
| Trimethoprim Enterobacteriaceae & Staphylococcus spp. | W | 5 | ≤10 | 11-15 | ≥16 |
| Trimethoprim-Sulfamethoxazole Enterobacteriaceae, Acinetobacter spp. & Staphylococcus spp., Haemophilus spp., Vibrio cholera, B. cepacia & S. maltophilia Neisseria meningitidis Streptococcus pneumoniae | SXT | 1.25/23.75 | ≤10 ≤25 ≤15 | 11-15 26-29 16-18 | ≥16 ≥30 ≥19 |
| Vancomycin Enterococcus spp. Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae | VA | 30 | ≤14 — | 15-16 — | ≥17 ≥17 |
Adapted in part with modification from the Clinical and Laboratory Standard Institute (CLSI) 2022 Document M100-S20 (M02-A10): Disc Diffusion Supplemental Tables Performance Standards for Antimicrobial susceptibility Testing. It is worthy of note that the above values are subject to change and updating based on the review panel of the CLSI, whose duty and mandate it is to make available the breakpoints of antibiotics used for antimicrobial susceptibility studies. Thus, readers are advised to always visit the website of CLSI (www.clsi.org/standards) for updated guidelines and protocols as it relates to breakpoints for antimicrobial susceptibility testing (AST).
