This group includes several important antibiotic classes used to treat a wide range of infections. Macrolides and aminoglycosides mainly work by blocking bacterial protein production, while polyene and polypeptide antibiotics damage cell membranes. These drugs are widely used in respiratory infections, severe gram-negative infections, and fungal diseases.
MACROLIDES
Macrolides are antibiotics with a large ring structure (macrolide ring). They are widely used as alternatives for patients allergic to penicillins.
Common Macrolides
- Erythromycin
- Azithromycin
- Clarithromycin
- Telithromycin (ketolide)
Mechanism of Action
Macrolides bind to the 50S ribosomal subunit of bacteria and block protein synthesis. They are mainly bacteriostatic but can be bactericidal at high concentrations.
Spectrum
- gram-positive bacteria
- some gram-negative bacteria
- atypical organisms like Chlamydia, Mycoplasma, Legionella
Uses
- Community-acquired pneumonia
- Streptococcal infections (in penicillin-allergic patients)
- Whooping cough (pertussis)
- Diphtheria
- Chlamydial infections
Side Effects
- Stomach upset (common with erythromycin)
- Cholestatic jaundice
- Hearing problems (rare)
- Liver toxicity (especially telithromycin)
AMINOGLYCOSIDES
Aminoglycosides are powerful, fast-acting antibiotics used mainly for severe gram-negative infections. They are usually given by injection.
Common Aminoglycosides
- Streptomycin
- Gentamicin
- Amikacin
- Tobramycin
- Neomycin
Mechanism of Action
Aminoglycosides bind irreversibly to the 30S ribosomal subunit, blocking protein synthesis and causing bacterial death. They are bactericidal.
Uses
- Serious gram-negative infections (e.g., Pseudomonas)
- Sepsis
- TB (streptomycin)
- Plague and tularemia
- Topical treatment (neomycin)
Side Effects
- Ototoxicity – hearing or balance damage
- Nephrotoxicity – kidney damage
- Neuromuscular blockade
Important Points
- Given by injection due to poor oral absorption
- Blood levels must be monitored
- Amikacin is most resistant to bacterial enzymes
POLYENE ANTIBIOTICS
Polyene antibiotics are antifungal agents that work by destroying fungal cell membranes.
Common Polyenes
- Amphotericin B
- Nystatin
Mechanism of Action
Polyene antibiotics bind to ergosterol in fungal cell membranes, forming pores that cause leakage of cell contents and fungal cell death.
Uses
- Systemic fungal infections (Amphotericin B)
- Oral and vaginal candidiasis (Nystatin)
Side Effects
Amphotericin B is known for significant toxicity:
- Fever and chills
- Kidney damage
- Low potassium levels
- Infusion-related reactions
Nystatin is safer because it is not absorbed from the gut or skin.
POLYPEPTIDE ANTIBIOTICS
These antibiotics damage bacterial cell membranes or cell wall formation.
Common Polypeptide Antibiotics
- Polymyxin B
- Colistin (Polymyxin E)
- Bacitracin
Mechanism of Action
Polymyxins bind to bacterial cell membranes, causing leakage and cell death. Bacitracin inhibits cell wall synthesis.
Uses
- Multidrug-resistant gram-negative infections (colistin)
- Topical use for skin infections (bacitracin, polymyxin B)
Side Effects
- Kidney toxicity (polymyxins)
- Nerve toxicity
- Allergic reactions (bacitracin)
Detailed Notes:
For PDF style full-color notes, open the complete study material below: