Canonical Question
Micro Pharm – Antibacterials
Master answer
Anti-staphylococcal antibiotics
| Class | Antibiotic | Mechanism of Action | Side Effects |
|---|---|---|---|
| Penicillin | Flucloxacillin | Beta lactam ring binds to penicillin binding protein (transpeptidase) and prevents crosslinking of bacterial peptidoglycan inhibits cell wall synthesis Bacteria eventually lyse due to ongoing activity of cell wall autolytic enzymes (autolysins and murein hydrolases) while cell wall assembly is arrested Less bactericidal but stable to staph beta-lactamases | Up to 10% of the population have allergies to penicillins. Due to the high percentage excreted renally unchanged dose adjustment is required in low urine output states. Severe cholestatic hepatitis has been reported idiosyncratically. |
| Glycopeptide | Vancomycin | Inhibits Glycopeptide synthetase prevents peptidoglycan formation in bacterial cell well (Unlike penicillins, prevents the transfer and addition of the muramylpentapeptide building blocks that make up the peptidoglycan molecule itself.) May also alter membrane permeability and selectively inhibit RNA synthesis. Antimicrobial activity Dependent on Duration above MIC, not concentration | Hypersensitivity reactions including anaphylaxis. Rapid infusion is associated with histamine release – red-man syndrome. Ototoxicity rare, dose related. Nephrotoxicity has declined with improved formulations, usually resolves with cessation of drug |
| Cephalosporin | Cefazolin | Beta lactam ring binds to multiple penicillin binding proteins (carboxy/endo/ transpeptidase) and prevents crosslinking of bacterial peptidoglycan inhibits cell wall synthesis BROADER SPECTRUM Bacteria eventually lyse due to ongoing activity of cell wall autolytic enzymes (autolysins and murein hydrolases) while cell wall assembly is arrested Configuration: Stability against Betalactamases | Generally well tolerated Hypersensitivity reactions (10% cross reactivity with penicillin allergies), thrombophlebitis, interstitial nephritis, low prothrombin, flushing and headaches with EtOH. |
| Lincosamide | Clindamycin | Inhibitor of bacterial 50S ribosomal subunit Prevents protein synthesis | – Pseudomembranous colitis due to c.diff – Contact dermatitis – Metallic taste – Anaphylaxis |
| Linezolid | Oxazolidinone | inhibits bacterial protein synthesis by binding specifically to the 50s ribosomal subunit, thereby preventing initiation complex formation. | Headache, LFT derangement, Taste Alteration, GI disturbances Skin/bleeding problems, phlebitis, pancreatitis |
Daptomycin, Rifampicin
Exam appearances
| Exam | Exact wording | Relationship | Success |
|---|---|---|---|
| 2022B Q09 | List any five classes of antibiotics with anti-staphylococcal activity and provide one example of each class. Outline the mechanism of action and side effects of the five drugs. | historical_member | — |