Introduction to Antibiotics

Introduction to Antibiotics

• Antibiotics are antimicrobial drugs inhibiting or killing bacteria.
• Crucial in treating bacterial infections.
• Target specific bacterial processes.
• Classification based on mechanism of action.
• Two main categories: Bacteriostatic and Bactericidal.

Types of Antibiotics

• Penicillins: Inhibit bacterial cell wall synthesis; examples include penicillin V and methicillin.
• Cephalosporins: Also target bacterial cell walls; showing resistance in some bacteria compared to Penicillins; examples include Cephalexin and Cefalosporin.
• Macrolides: Affect bacterial protein synthesis; examples include erythromycin and azithromycin.
• Tetracyclines: Inhibit protein synthesis, known for broad-spectrum action; examples include doxycycline and tetracycline.
• Aminoglycosides: Affect bacterial protein synthesis, often used in severe infections; examples include gentamicin and streptomycin.
• Quinolones: Inhibit bacterial DNA gyrase activity; examples include ciprofloxacin and levofloxacin.
• Sulfonamides: Inhibit folic acid synthesis in bacteria.
• Lincosamides: Inhibit bacterial protein synthesis.
• Glycopeptides: Inhibit bacterial cell wall synthesis, often used for serious infections; example Vancomycin.

Bacteriostatic Antibiotics

• Inhibit bacterial growth and replication, not directly killing the bacteria.
• Host's immune system eliminates the bacteria.
• Often used for infections where the immune response is sufficient.
• Effective against rapidly multiplying bacteria; Example: Tetracyclines.

Bactericidal Antibiotics

• Directly kill bacteria by targeting essential bacterial processes.
• Often used in severe infections or when the immune system is compromised.
• Effective against bacteria that can persist in lower concentrations.
• Effective in infections with higher bacterial load; Example: Penicillins.

Mechanisms of Actions

• Inhibit cell wall synthesis: Preventing the formation of the bacterial cell wall, crucial for structural integrity and preventing osmotic lysis. Includes penicillins, cephalosporins, and vancomycin.
• Interfering with protein synthesis: Disrupting bacterial protein production, crucial for bacterial growth and reproduction; Includes tetracyclines, aminoglycosides, and macrolides.
• Inhibiting DNA/RNA replication: Stopping bacterial DNA or RNA synthesis, impeding the bacteria's ability to replicate and divide; Includes quinolones and rifampin.
• Blocking folic acid synthesis: Essential pathways for DNA and RNA production.
• Inhibiting metabolic pathways: Hindering bacterial ability to generate energy or produce essential metabolites. This mechanism shows vast variations depending on the target bacteria.

Resistance Mechanisms

• Overuse and misuse contribute to bacterial resistance.
• Mutations in bacterial genes lead to resistance.
• Enzymatic inactivation (degradation) of antibiotics by some bacteria.
• Transfer of resistant genes between bacteria (horizontal gene transfer).
• Bacterial resistance to antimicrobial agents is an implication.

Factors Influencing Efficacy

• Efficacy depends on the type of bacteria, antibiotic susceptibility, dosage, administration route, and treatment duration.
• Drug resistance poses significant treatment challenges.
• Different bacteria exhibit varying susceptibility, often determined by laboratory testing.

Spectrum of Activity

• Broad-spectrum antibiotics have activity against many bacterial species; potentially harming beneficial gut bacteria.
• Narrow-spectrum antibiotics have activity against a limited group of bacterial species; more specific to certain bacterial targets and potentially safer for gut microbiota.

Importance of Proper Use

• Careful antibiotic use is crucial to avoid resistance development.
• Prescribing antibiotics requires understanding of the infecting organism and available treatments.
• Prolonged or inappropriate use promotes antibiotic-resistant strains, diminishing treatment effectiveness.
• Antibiotics are ineffective against viral infections; use should be restricted to bacterial infections.