3. Penicillins Mechanism of Action Inhibit bacterial cell wall synthesis by binding penicillin-binding proteins (PBPs). Antibacterial Spectrum Mainly Gram-positive bacteria. Some Gram-negative organisms. Classification Natural: Penicillin G, Penicillin V. Penicillinase-resistant: Oxacillin, Cloxacillin. Aminopenicillins: Ampicillin, Amoxicillin. Antipseudomonal: Piperacillin, Ticarcillin. Therapeutic Uses Streptococcal infections. Syphilis. Meningitis. Respiratory and urinary tract infections. Resistance β-lactamase production. Altered PBPs. Reduced permeability. Adverse Effects Hypersensitivity reactions. Rash. Diarrhea. Anaphylaxis. 4. Cephalosporins Mechanism of Action Inhibit bacterial cell wall synthesis. Antibacterial Spectrum Broad-spectrum activity. Later generations have greater Gram-negative coverage. Classification 1st: Cefazolin, Cephalexin. 2nd: Cefuroxime. 3rd: Ceftriaxone, Ceftazidime. 4th: Cefepime. 5th: Ceftaroline. Therapeutic Uses Pneumonia. Meningitis. Sepsis. Urinary tract infections. Resistance β-lactamases. Altered PBPs. Adverse Effects Allergy. Diarrhea. Superinfection. Rare nephrotoxicity. 5. Carbapenems Mechanism of Action Inhibit bacterial cell wall synthesis. Classification Imipenem. Meropenem. Ertapenem. Doripenem. Antibacterial Spectrum Very broad spectrum. Effective against Gram-positive, Gram-negative and anaerobic bacteria. Therapeutic Uses Severe hospital-acquired infections. Sepsis. Complicated intra-abdominal infections. Resistance Carbapenemase enzymes. Efflux pumps. Porin mutations. Adverse Effects Nausea. Diarrhea. Rash. Seizures (especially imipenem). 6. Tetracyclines Mechanism of Action Bind 30S ribosomal subunit and inhibit protein synthesis. Classification Tetracycline. Doxycycline. Minocycline. Antibacterial Spectrum Broad spectrum. Effective against atypical organisms. Therapeutic Uses Acne. Cholera. Rickettsial infections. Chlamydia. Lyme disease. Resistance Efflux pumps. Ribosomal protection proteins. Adverse Effects Gastrointestinal irritation. Photosensitivity. Teeth discoloration. Hepatotoxicity. 7. Aminoglycosides Mechanism of Action Irreversibly bind 30S ribosomal subunit causing defective protein synthesis. Classification Gentamicin. Amikacin. Tobramycin. Streptomycin. Antibacterial Spectrum Mainly aerobic Gram-negative bacilli. Therapeutic Uses Severe systemic infections. Tuberculosis (streptomycin). Sepsis. Resistance Drug-inactivating enzymes. Ribosomal mutations. Adverse Effects Nephrotoxicity. Ototoxicity. Neuromuscular blockade. 8. Macrolides Mechanism of Action Bind 50S ribosomal subunit and inhibit protein synthesis. Classification Erythromycin. Clarithromycin. Azithromycin. Antibacterial Spectrum Gram-positive cocci. Atypical organisms. Therapeutic Uses Respiratory tract infections. Mycoplasma pneumonia. Chlamydial infections. Resistance Ribosomal modification. Efflux pumps. Adverse Effects Nausea. Diarrhea. QT prolongation. Cholestatic hepatitis. 9. Quinolones Mechanism of Action Inhibit DNA gyrase and topoisomerase IV. Classification Ciprofloxacin. Levofloxacin. Moxifloxacin. Ofloxacin. Antibacterial Spectrum Broad-spectrum activity. Excellent Gram-negative coverage. Therapeutic Uses UTIs. Gastrointestinal infections. Respiratory infections. Resistance DNA gyrase mutations. Efflux pumps. Adverse Effects Tendon rupture. QT prolongation. Gastrointestinal upset. CNS effects. 10. Sulfonamides Mechanism of Action Inhibit folic acid synthesis by blocking dihydropteroate synthase. Classification Sulfamethoxazole. Sulfadiazine. Sulfisoxazole. Antibacterial Spectrum Broad-spectrum bacteriostatic agents. Therapeutic Uses Urinary tract infections. Pneumocystis jirovecii pneumonia. Toxoplasmosis. Resistance Altered enzyme. Increased PABA production. Adverse Effects Hypersensitivity. Stevens–Johnson syndrome. Hemolysis in G6PD deficiency. Crystalluria. Compare the given information about antimicrobial and antiviral drug by making a single comparative chart, a) cell wall synthesis inhibition - Q3, Q4 & Q5. B) protein synthesis inhibition - Q7, Q6 & Q8 . C) DNA/RNA synthesis inhibition - Q9. D) metabolic pathway inhibition - Q10 (all from given data)
Antimicrobial Drugs: Comparative Chart by Mechanism of Action
A) Cell Wall Synthesis Inhibition
| Feature | Penicillins (Q3) | Cephalosporins (Q4) | Carbapenems (Q5) |
|---|---|---|---|
| Mechanism | Bind PBPs, inhibit cell wall synthesis | Inhibit cell wall synthesis (bind PBPs) | Inhibit cell wall synthesis (bind PBPs) |
| Spectrum | Mainly Gram-positive; some Gram-negative | Broad; later generations = more Gram-negative | Very broad: Gram+, Gram-, anaerobes |
| Key Classes | Natural, Penicillinase-resistant, Aminopenicillins, Antipseudomonal | 1st-5th generation | Imipenem, Meropenem, Ertapenem, Doripenem |
| Key Drugs | Pen G/V, Oxacillin, Ampicillin, Piperacillin | Cefazolin, Ceftriaxone, Cefepime, Ceftaroline | Imipenem, Meropenem, Ertapenem, Doripenem |
| Therapeutic Uses | Strep infections, syphilis, meningitis, RTI, UTI | Pneumonia, meningitis, sepsis, UTI | Severe HAI, sepsis, complicated intra-abdominal infections |
| Resistance | β-lactamase, altered PBPs, reduced permeability | β-lactamases, altered PBPs | Carbapenemases, efflux pumps, porin mutations |
| Adverse Effects | Hypersensitivity, rash, diarrhea, anaphylaxis | Allergy, diarrhea, superinfection, rare nephrotoxicity | Nausea, diarrhea, rash, seizures (esp. imipenem) |
| Notable Concern | Anaphylaxis risk | Cross-reactivity with penicillins (~1-2%) | Imipenem lowers seizure threshold |
B) Protein Synthesis Inhibition
| Feature | Aminoglycosides (Q7) | Tetracyclines (Q6) | Macrolides (Q8) |
|---|---|---|---|
| Mechanism | Irreversibly bind 30S subunit - defective protein synthesis | Bind 30S subunit - inhibit protein synthesis | Bind 50S subunit - inhibit protein synthesis |
| Binding Site | 30S ribosomal subunit | 30S ribosomal subunit | 50S ribosomal subunit |
| Action Type | Bactericidal | Bacteriostatic | Bacteriostatic |
| Spectrum | Mainly aerobic Gram-negative bacilli | Broad; atypical organisms | Gram-positive cocci; atypical organisms |
| Key Drugs | Gentamicin, Amikacin, Tobramycin, Streptomycin | Tetracycline, Doxycycline, Minocycline | Erythromycin, Clarithromycin, Azithromycin |
| Therapeutic Uses | Severe systemic infections, TB (streptomycin), sepsis | Acne, cholera, rickettsial infections, chlamydia, Lyme disease | RTI, Mycoplasma pneumonia, chlamydial infections |
| Resistance | Drug-inactivating enzymes, ribosomal mutations | Efflux pumps, ribosomal protection proteins | Ribosomal modification, efflux pumps |
| Adverse Effects | Nephrotoxicity, ototoxicity, neuromuscular blockade | GI irritation, photosensitivity, teeth discoloration, hepatotoxicity | Nausea, diarrhea, QT prolongation, cholestatic hepatitis |
| Notable Concern | Narrow therapeutic index; monitor renal function | Avoid in children/pregnancy (teeth/bone) | QT prolongation; drug interactions (CYP450) |
C) DNA/RNA Synthesis Inhibition
| Feature | Quinolones (Q9) |
|---|---|
| Mechanism | Inhibit DNA gyrase and topoisomerase IV |
| Spectrum | Broad-spectrum; excellent Gram-negative coverage |
| Key Drugs | Ciprofloxacin, Levofloxacin, Moxifloxacin, Ofloxacin |
| Therapeutic Uses | UTIs, GI infections, respiratory infections |
| Resistance | DNA gyrase mutations, efflux pumps |
| Adverse Effects | Tendon rupture, QT prolongation, GI upset, CNS effects |
| Notable Concern | Avoid in children/pregnancy; tendon rupture risk (esp. with corticosteroids) |
D) Metabolic Pathway Inhibition
| Feature | Sulfonamides (Q10) |
|---|---|
| Mechanism | Block dihydropteroate synthase - inhibit folic acid synthesis |
| Spectrum | Broad-spectrum bacteriostatic |
| Key Drugs | Sulfamethoxazole, Sulfadiazine, Sulfisoxazole |
| Therapeutic Uses | UTIs, Pneumocystis jirovecii pneumonia, toxoplasmosis |
| Resistance | Altered enzyme, increased PABA production |
| Adverse Effects | Hypersensitivity, Stevens-Johnson syndrome, hemolysis (G6PD deficiency), crystalluria |
| Notable Concern | Life-threatening SJS risk; avoid in G6PD-deficient patients |
Quick Summary Reference
| Mechanism | Drug Classes | Ribosomal Target |
|---|---|---|
| Cell wall synthesis inhibition | Penicillins, Cephalosporins, Carbapenems | N/A |
| Protein synthesis inhibition (30S) | Aminoglycosides, Tetracyclines | 30S subunit |
| Protein synthesis inhibition (50S) | Macrolides | 50S subunit |
| DNA/RNA synthesis inhibition | Quinolones | DNA gyrase / Topo IV |
| Metabolic pathway inhibition | Sulfonamides | Dihydropteroate synthase (folate pathway) |