Antibiogram & Interpretative Standards for Antibiotic (Antibacterial) Disks used for Susceptibility Studies

Antimicrobial Agents /
Microorganisms
 Disk Code Disk Potency (µg)  Resistant  Intermediate  Susceptible
Amikacin
Enterobacteriaceae, P. aeruginosa Acinetobacter spp, Staphylococcus spp    
AK30    ≤1415-16≥17
Amoxycillin-Clavulanic acid
Enterobacteriaceae
Staphylococcus spp    
Haemophilus spp
AMC20/10≤13
≤19
≤19
  14-17

  ≥18
≥20
≥20
Ampicillin
Enterobacteriaceae and Vibrio cholerae Staphylococcus spp   
Enterococcus spp
Haemophilus spp
Streptococcus spp. β-haemolytic Group
AMP10≤13
≤28
≤16
≤18
14-16


19-21
≥17
≥29
≥17
≥22
≥24
Ampicillin-Sulbactam
Enterobacteriaceae, Acinetobacter spp., & Staphylococcus spp.
Haemophilus spp.  
SAM10/10 
≤11  

≤19

12-14  


≥15  

≥20
Azithromycin
Staphylococcus spp., Streptococcus spp             Viridans Group, β-haemolytic Group, and            
S. pneumoniae      
Neisseria meningitidis
Haemophilus spp.   
AZM15


≤13

     


14-17




≥18
≥20
≥12
Aztreonam
Enterobacteriaceae
Pseudomonas aeruginosa
Haemophilus spp.
ATM30
≤17
≤15

18-20
16-21

≤21
≥22
26
Carbenicillin
Enterobacteriaceae
Pseudomonas aeruginosa
CAR100
≤19
≤13

20-22
14-16

≥23
≥17
Cefaclor
Enterobacteriaceae & Staphylococcus spp.
Haemophilus spp.
CEC30
≤14
≤16

15-17
17-19

≥18
≥20
Cefamandole
Enterobacteriaceae & Staphylococcus spp.
MA30 
≤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  
FEP30≤14



≤21  
15-17



22-23
 ≥18
≥26
≥31
≥24
≥24
Cefixime
Enterobacteriaceae
Haemophilus spp.
Neisseria gonorrhoeae 
CFM5
≤15


16-18


≥19
≥21
≥31
Cefonicid
Enterobacteriaceae & Staphylococcus spp.
Haemophilus spp.
CID30
≤14
≤16

15-17
17-19

≥18
≥20
Cefoperazone
Enterobacteriaceae, P. aeruginosa &             Staphylococcus spp.
CFP75  ≤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   
CTX30

≤22
≤14  




≤25


23-25
15-22  




26-27


≥26
≥23  
≥26
≥34
≥31
≥24
≥28
Cefotetan  
Enterobacteriaceae & Staphylococcus spp.
Neisseria gonorrhoeae
CTT30
≤12
≤19

13-15
20-25

≥16
≥26
Cefoxitin
Enterobacteriaceae
S. aureus & S. lugdunensis
Coagulase-negative Staphylococci
Neisseria gonorrhoeae
FOX30
≤14
≤21
≤24
≤23

15-17


24-27

≥18
≥22
≥25
≥28
Cefpodoxime
Enterobacteriaceae & Staphylococcus spp.
Haemophilus spp.
Neisseria gonorrhoeae
CPD10
≤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
CAZ30

≤17  
≤14
≤17      
—      


18-20  
15-17
18-20
—         


≥21  
≥18
≥21
≥26
≥31
Ceftizoxime
Enterobacteriaceae
P. aeruginosa & Staphylococcus spp.
Haemophilus spp.
Neisseria gonorrhoeae
ZOX30
≤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   
CRO30

≤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
CXM30
≤14
≤16
≤25

15-17
17-19
26-30

≥18
≥20
≥31
Cephalothin
Enterobacteriaceae & Staphylococcus spp.
KF30  ≤1415-17 
≥18
Chloramphenicol
Enterobacteriaceae, staphylococcus spp.             Enterococcus spp., & Vibrio cholera
Haemophilus spp.
Neisseria meningitidis
Streptococcus pneumoniae
Streptococcus spp. Viridans group & β-haemolytic group    
C30

≤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
CIP5

≤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
CLR15

≤13
≤10  
≤16


14-17
11-12  
17-20


≥18
≥13  
≥21
Clindamycin
Staphylococcus spp.
Streptococcus spp. Viridans group, β-haemolytic group & S. pneumoniae
DA2

≤14  
≤15


15-20  
16-18


≥21  
≥19
Colistin
Pseudomonas aeruginosa
CT10
≤10


≥11
DoripenemDOR10
Doxycycline
Enterobacteriaceae
Acinetobacter spp.
Staphylococcus spp. & Enterococcus spp.
DO30
≤10
≤9
≤12

11-13
10-12
13-15

≥14
≥13
≥16
Ertapenem
Enterobacteriaceae & Staphylococcus spp.
Haemophilus spp.
ETP10
≤15

16-18

≥19
≥19
Erythromycin
Staphylococcus spp. & Enterococcus spp.
Streptococcus spp. Viridans group, β-haemolytic group & S. pneumoniae
E15≤13  
≤15
14-22  
16-20
≥23  
≥21
Gentamicin
Enterobacteriaceae, P. aeruginosa, Acinetobacter Spp., and Staphylococcus spp.
CN10  ≤1213-14≥15
Imipenem
Enterobacteriaceae, P. aeruginosa, Acinetobacter Spp., & Staphylococcus spp.
Haemophilus spp.
IPM10

≤13  


14-15  

≥16  
≥16
Kanamycin
Enterobacteriaceae & Staphylococcus spp.
K30 
≤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.
LEV5



≤13  
≤15




14-16  
16-18




≥17  
≥19
≥17
Linezolid
Staphylococcus spp.
Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae
Enterococcus spp.
LZD30

≤20
—      
≤20



—  
21-22


≥21
≥21  
≥23
Lomefloxacin
Enterobacteriaceae, P. aeruginosa & Staphylococcus spp.
Haemophilus spp.
Nesseria gonorrhoeae
LOM10

≤18  

≤26


19-21  

23-37


≥22  
≥22
≥38
Mecillinam
Enterobacteriaceae
MEL10
≤11

12-14

≥15
Meropenem
Enterobacteriaceae, P. aeruginosa, Acinetobacter Spp., & Staphylococcus spp.
B. cepacia
Neisseria meningitidis
Haemophilus spp.
MEM10

≤13
≤15



14-15
16-19



≥16
≥20
≥30
≥20
Meziocillin
Enterobacteriaceae & Acinetobacter spp.
Pseudomonas aeruginosa
MEZ75
≤17
≤15

18-20

≥21
≥16
Minocycline
Enterobacteriaceae, P. aeruginosa & Acinetobacter spp.
Neisseria meningitidis
S. maltophila, B. cepacia, Staphylococcus spp., & Enterococcus spp.
MH30


≤12  
—  
≤14



13-15  
—  
15-18



≥16  
≥26  
≥19
Moxifloxacin
Staphylococcus spp.
Streptococcus pneumoniae
Haemophilus spp.
MFX5

≤20
≤14


21-23
15-17


≥24
≥18
≥18
Nafcillin
Staphylococcus aureus
NF1 
≤10
 
11-12

≥13
Nalidixic acid
Enterobacteriaceae
Neisseria meningitidis
NA30
≤13
≤25

14-18

≥19
≥26
Netilmicin
Enterobacteriaceae, P. aeruginosa, & Staphylococcus spp.
NET30   
≤12

13-14

≥15
Nitrofurantoin
Enterobacteriaceae, Staphylococcus spp., Enterococcus spp.
F300   
≤14

15-16

≥17
Norfloxacin
Enterobacteriaceae, P. aeruginosa, Staphylococcus spp., & Enterococcus spp.
NOR10
≤12

13-16

≥17
Ofloxacin
Enterobacteriaceae, P. aeruginosa, & Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae
Staphylococcus spp.
Haemophilus spp.
Neisseria gonorrhoeae
OFX5


≤12  
≤14

≤24



13-15  
15-17

25-30



≥16  
≥18
≥16
≥31
Oxacillin
S. aureus
S. pneumoniae (for penicillin susceptibility)
OX1 
≤10

11-12

≥13
≥20
Penicillin
Staphylococcus spp.
Enterococcus spp.
Neisseria gonorrhoeae
Streptococcus spp. β-haemolytic group
P10
≤28
≤14
≤26  



27-46  

≥29
≥15
≥47  
≥24
Piperacillin
Enterobacteriaceae & Acinetobacter spp.
Pseudomonas aeruginosa
PRL100
≤17
≤17

18-20

≥21
≥18  
Piperacillin-Tazobactam
Enterobacteriaceae & Acinetobacter spp.
Pseudomonas aeruginosa
Staphylococcus spp.
Haemophilus spp.
TZP100/10

≤17
≤17
≤17


18-20




≥21
≥18
≥18
≥21
Polymyxin B
Pseudomonas aeruginosa
PB300
≤11


≥12
Quinupristin-Dalfopristin
Staphylococcus spp., Enterococcus spp., & Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae
QD15
≤15

16-18
   
≥19  
Rifampin
Staphylococcus spp., Enterococcus spp., & Haemophilus spp.
Neisseria  meningitidis
Streptococcus pneumoniae
RD5

≤16
≤19
≤16


17-19
20-24
17-18


≥20
≥25
≥19
Spectinomycin
Neisseria gonorrhoeae
SH100
≤14

15-17

≥18
Streptomycin
Enterobacteriaceae
S10
≤11

12-14

≥15
Sulfisoxazole
Enterobacteriaceae, Staphylococcus spp. & Vibrio cholera
SFX300
≤12

13-16

≥17
Telithromycin
Staphylococcus spp.
Haemophilus spp.
Streptococcus pneumoniae
TEL15
≤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
TE30


≤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
TIC75 
≤14
≤14

15-19

≥20
≥15
Ticarcillin-Clavulanic Acid
Enterobacteriaceae & Acinetobacter spp.
Pseudomonas aeruginosa
Staphylococcus spp.
TIM75/10
≤14
≤14
≤22

15-19


≥20
≥15
≥23
TigecylineTGC15
Tobramycin
Enterobacteriaceae & P. aeruginosa
Acinetobacter spp. & Staphylococcus spp.
TOB10≤1213-14≥15
Trimethoprim
Enterobacteriaceae & Staphylococcus spp.
 W5 
≤10

11-15

≥16
Trimethoprim-Sulfamethoxazole
Enterobacteriaceae, Acinetobacter spp. & Staphylococcus spp., Haemophilus spp., Vibrio cholera, B. cepacia & S. maltophilia
Neisseria  meningitidis
Streptococcus pneumoniae
SXT1.25/23.75


≤10
≤25
≤15



11-15
26-29
16-18



≥16
≥30
≥19
Vancomycin
Enterococcus spp.
Streptococcus spp. Viridians group, β-haemolytic group, & S. pneumoniae
VA30

≤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).


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