Classification of antibiotics

Classification of antibiotics

Antibiotics: Antibiotics are the chemical therapeutic agents of microbial or synthetic or semi-synthetic origin which in lower concentration inhibit the growth of other microorganisms.

Classification of antibiotics

A] On the basis of chemical structure

B] On the basis of origin

C] On the basis of range of activity ( spectrum of activity)

D] On the basis of mode of action

E] On the basis of effects of their activity

F] On the basis of route of administration


A] Classification of antibiotics on the basis of chemical structure:

  1. Carbohydrate containing Antibiotics:
  2. Pure saccharides antibiotics: examples; Streptozotocin
  3. Aminoglycosides: examples; Streptomycin
  4. N/O glycosides: eg. Chromomycin
  5. Other: eg; Lincomycin
  6. Macrocyclic lactone antibiotics: eg. Erythromycin
  7. Quinolones antibiotics; eg. Fluroquinolone
  8. N-containing heterocyclic antibiotics: eg. Beta-lactum
  9. O-containing heterocyclic antibiotics: eg. Cycloserine
  10. Alicyclic antibiotics: eg. Cycloheximide
  11. Aromatic antibiotics (Nitrobenzene): eg. Chloramphenicol
  12. Aliphatic amine antibiotics: eg. Spermidine
  13. Peptide antibiotics: eg. Polymyxin, Bacitracin, Gramicidin


B] Classification of antibiotics on the basis of origin:

1.Microbial origin:

i. Bacterial origin:

Bacillus polymyxa: Polymyxin

Chromobacter violaceum: Bacitracin

Micromonospora spp: Gentamycin

ii. Fungal origin:

Penicillium notatum: Penicillin

Cephalosporin spp: Cephalosporin

iii. Actimomycetes origin:

Streptomyces griseus: Streptomycin

S. venezuelue: Chloramphenicol

S. erythreus: Erythromycin

S. mediterranae: Rifampicin


2. Semi-synthetic antibiotics:

  • Examples: Amoxycillin, Ampicillin, Doxycycline, Tigecycline, Sulfonamide etc

3. Synthetic antibiotics:

  • Examples: Chloramphenicol, 4-quinolones, Sulfonamide


C] Classification of antibiotics on the basis of range of activity (spectrum of activity):

1.Narrow spectrum:

  • Active towards relatively fewer microorganisms.
  • Examples: macrolides, Polymyxin

2. Moderate spectrum:

  • Active towards Gram Positive bacteria as well as some systemic and UTI causing Gram negative bacteria.
  • Examples: Aminoglycosides, Sulfonamide

3. Narrow-Broad spectrum:

  • Active against Gram positive and gram negative
  • Examples: Beta-lactum

4. Broad spectrum:

  • Active against Gram positive and Gram negative except Pseudomonas and Mycobacteria.
  • Examples: Chloramphenicol, Tetracycline

5. Anti-mycobacterial antibiotics:

  • Examples: Ethambutol, Rifampicin, Isoniazid, Pyrazinamide


D] Classification of antibiotics on the basis of Mode of action:

1. Inhibitor of cell wall synthesis/ Peptidoglycan Inhibitors:


  • Beta-lactum; Penicillin
  • Bacitracin
  • Cycloserine
  • Phosphomycin
  • Cephalosporin
  • Vancomycin

2. Inhibitor of protein synthesis:


  • Streptomycin
  • Aminoglycosides
  • Fusidic acid
  • Tetracycline
  • Mupirocin
  • Chloramphenicol
  • Macrolides

3. Inhibitor of Nucleic acid synthesis:


  • Quinolones
  • Ciprofloxacin
  • Nalidixic acid
  • Metronidazole
  • Nitrofurantoin

4. Inhibitor of folic acid synthesis (Folate antagonistic)


  • Sulfonamide
  • Trimethoprim

5. Inhibitor of cytoplasmic membrane:


  • Polymyxin; Colistin


E] Classification of antibiotics on the basis of effects of their activity:

1. Bactericidal:

  • Kills bacteria
  • Examples: Aminoglycosides, Penicillin, Cephalosporin

2. Bacteriostatic:

  • Inhibits the growth of bacteria
  • Examples: Sulfonamide, tetracycline, chloramphenicol, trimethoprim, macrolides, Lincosamide


F] Classification of antibiotics on the basis of Route of administration:

1. Oral antibiotics:

  • Acid stable antibiotics,
  • Examples; Penicillin V

2. Parenteral route:

  • Intravenous administration
  • Examples; Penicillin G

Classification of antibiotics

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