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

S. venezuelae: Chloramphenicol

2. Semi-synthetic antibiotics:

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

3. Synthetic antibiotics:

• Examples: Chloramphenicol (* it was extracted from Streptomyces venzuelae but now produced synthetically), 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:

Examples:

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

2. Inhibitor of protein synthesis:

Examples:

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

3. Inhibitor of Nucleic acid synthesis:

Examples:

• Quinolones
• Ciprofloxacin
• Nalidixic acid
• Metronidazole
• Nitrofurantoin

4. Inhibitor of folic acid synthesis (Folate antagonistic)

Examples:

• Sulfonamide
• Trimethoprim

5. Inhibitor of cytoplasmic membrane:

Examples:

• 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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