Antibiotics and Resistance

Selective Toxicity

• Early treatments for infections were often more harmful than the disease itself.
• Paul Ehrlich introduced the concept of a 'magic bullet' to kill microbial cells without harming the host.
• Selective toxicity targets bacterial cells while minimizing harm to host cells.

Penicillin

• Alexander Fleming discovered penicillin in 1928, observing its ability to destroy Staphylococcus bacteria.
• Penicillin inhibits bacterial cell wall formation by interfering with peptidoglycan cross-links.

Antibiotic Targets

• Antibiotics target various bacterial cell components:
  1. Cell wall synthesis (e.g., penicillins)
  2. Protein synthesis (e.g., aminoglycosides)
  3. Cell membrane function (e.g., polymyxins)
  4. Nucleic acid synthesis (e.g., quinolones)

Antibiotic Resistance Mechanisms

• Mutations lead to genetic diversity, causing antibiotic resistance.
• Bacteria resist antibiotics through:
  1. Enzyme inactivation (e.g., beta-lactamase).
  2. Reduced drug accumulation.
  3. Altered target affinity.

Beta-Lactamase

• Beta-lactamase is an enzyme that destroys penicillin by breaking the β-lactam ring.

Gene Transfer

• Horizontal gene transfer contributes to antibiotic resistance through:
  1. Transformation
  2. Transduction
  3. Conjugation

Reducing Antibiotic Resistance

• Strategies to reduce antibiotic resistance include:
  1. Decreasing antibiotic utilization.
  2. Improving hygiene and infrastructure.
  3. Enhancing diagnostics.
  4. Identifying new drug targets.
  5. Using combination therapies.

Antibiotic Usage Statistics

• 80% of antibiotics are given to livestock to promote growth and prevent diseases.
• 50% of antibiotics prescribed to humans are unnecessary or inappropriately used.