Antibiotics: Classification, Mechanism, Type of Action & Antimicrobial Spectrum
Antibiotics are agents used to treat bacterial infections by either killing bacteria (bactericidal) or inhibiting their growth (bacteriostatic).
Principles of Rational Antibiotic Therapy
- Correct Diagnosis: Ensure bacterial origin of infection before starting antibiotics
- Appropriate Drug Selection: Choose based on likely organisms & resistance patterns
- Correct Dose & Duration: Avoid under/over-treatment to prevent resistance
- Route of Administration: Oral for mild/moderate; IV for severe/systemic infections
- Monitoring & Adjustment: Modify based on clinical response and lab reports
- Avoid Overuse: Especially of broad-spectrum agents to reduce resistance risk
Principles of Antibiotic Prophylaxis
- Use only when indicated (e.g., surgical procedures, immunocompromised patients)
- Administer 1 hour before surgery to ensure optimal tissue levels
- Choose antibiotics based on likely pathogens
- Limit duration (usually single preoperative dose or <24 hrs post-op)
- Review practices regularly according to local resistance data and guidelines
Recap Questions
- 1. Which class of antibiotics inhibits DNA gyrase and topoisomerase IV?
- 2. Which antibiotics are effective against atypical organisms like Mycoplasma?
- 3. Name one narrow-spectrum antibiotic effective against MRSA.
- 4. What is the type of action of aminoglycosides?
- 5. What is the ideal timing for giving antibiotics as surgical prophylaxis?