What are the 5 main mechanisms of antibiotic action? 🦠
1️⃣ Inhibition of Cell Wall Synthesis 🧱 (e.g. beta-lactams, glycopeptides)
2️⃣ Inhibition of Protein Synthesis 🛑 (e.g. aminoglycosides, tetracyclines)
3️⃣ Inhibition of Nucleic Acid Synthesis 🧬 (e.g. fluoroquinolones, rifamycins)
4️⃣ Inhibition of Metabolic Pathways 🦠 (e.g. sulfonamides, trimethoprim)
5️⃣ Disruption of Cell Membrane Integrity ⛓️💥 (e.g. polymyxins, daptomycin)
Give examples of antibiotics that inhibit cell wall synthesis 🧱
🔹 Beta-lactams: penicillin, ceftriaxone, meropenem (bind PBPs)
🔹 Glycopeptides: vancomycin, teicoplanin (bind D-Ala-D-Ala)
🔹 Monobactams: aztreonam (Gram-negative only)
Which antibiotics act on the 30S ribosomal subunit? 🛑
🔹 Aminoglycosides (gentamicin, amikacin) – bactericidal
🔹 Tetracyclines (doxycycline, tigecycline) – usually bacteriostatic
Which antibiotics act on the 50S ribosomal subunit? 🛑
🔹 Macrolides (azithromycin, clarithromycin)
🔹 Lincosamides (clindamycin)
🔹 Oxazolidinones (linezolid)
Give examples of antibiotics that inhibit nucleic acid synthesis 🧬
🔹 Fluoroquinolones (ciprofloxacin, levofloxacin) – inhibit DNA gyrase/topoisomerase IV
🔹 Rifamycins (rifampicin) – inhibit RNA polymerase
🔹 Nitroimidazoles (metronidazole) – DNA strand breakage
Give examples of antibiotics that inhibit metabolic pathways 🦠
🔹 Sulfonamides – inhibit dihydropteroate synthase
🔹 Trimethoprim – inhibits dihydrofolate reductase
💡 Often combined as co-trimoxazole for synergy
Give examples of antibiotics that disrupt cell membrane integrity ⛓️💥
🔹 Polymyxins (colistin, polymyxin B) – Gram-negative MDR, nephro/neurotoxic
🔹 Daptomycin – Gram-positive resistant, inactivated by lung surfactant
What is MIC and why is it important?
💡 Minimum Inhibitory Concentration: lowest antibiotic concentration that prevents visible bacterial growth.
📌 Determines dosing strategies to keep drug above MIC for effective bacterial kill.
What are time-dependent antibiotics? ⏳
🧱 Aim: Keep concentration above MIC for as long as possible in dosing interval
💊 Examples: beta-lactams, vancomycin
💡 ICU: prolonged/continuous infusions improve efficacy
What are concentration-dependent antibiotics? 📈
📌 Aim: High peak:Cmax ratio for best kill
💊 Examples: aminoglycosides
✅ Dose once daily to maximise peak and reduce toxicity
What are AUC-dependent antibiotics? 📊
📌 Aim: Optimise total exposure (AUC:MIC)
💊 Examples: fluoroquinolones, vancomycin, linezolid
💡 TDM needed for vancomycin (AUC:MIC >400)
What are the 4 major mechanisms of antimicrobial resistance? 🧬
1️⃣ Enzymatic degradation/modification (e.g. beta-lactamases)
2️⃣ Altered target site (e.g. MRSA altered PBP2a)
3️⃣ Efflux pumps (e.g. Pseudomonas)
4️⃣ Reduced permeability (e.g. porin loss in Gram-negatives)
Give examples of common resistant organisms in ICU 🏥
🔹 MRSA – mecA gene → altered PBP2a
🔹 VRE – altered peptidoglycan terminus
🔹 ESBL Enterobacteriaceae – hydrolyse beta-lactams
🔹 CRE – carbapenemases
🔹 MDR Pseudomonas & Acinetobacter
🔹 Azole-resistant Candida (C. auris)
What are the main challenges of fungal infection in ICU? 🍄
🚧 Non-specific presentation
⏳ Delayed/difficult diagnosis
📈 Rising incidence in immunosuppression, devices, TPN
💊 Limited antifungal options + resistance
⚠️ High mortality
What are the 5 main mechanisms of antibiotic action? 🦠
1️⃣ Inhibition of Cell Wall Synthesis 🧱 (beta-lactams, glycopeptides, monobactams)
2️⃣ Inhibition of Protein Synthesis 🛑 (aminoglycosides, tetracyclines, macrolides, clindamycin, linezolid)
3️⃣ Inhibition of Nucleic Acid Synthesis 🧬 (fluoroquinolones, rifampicin, metronidazole)
4️⃣ Inhibition of Metabolic Pathways 🦠 (sulfonamides, trimethoprim)
5️⃣ Disruption of Cell Membrane Integrity ⛓️💥 (polymyxins, daptomycin)
Give examples of cell wall synthesis inhibitors 🧱
🔹 Beta-lactams: penicillin, ceftriaxone, meropenem (bind PBPs)
🔹 Glycopeptides: vancomycin, teicoplanin (bind D-Ala-D-Ala)
🔹 Monobactams: aztreonam (Gram-negative only)
Which antibiotics act on 30S ribosomal subunit? 🛑
🔹 Aminoglycosides (gentamicin, amikacin) – bactericidal
🔹 Tetracyclines (doxycycline, tigecycline) – bacteriostatic
Which antibiotics act on 50S ribosomal subunit? 🛑
🔹 Macrolides (azithromycin, clarithromycin)
🔹 Lincosamides (clindamycin)
🔹 Oxazolidinones (linezolid)
Give examples of nucleic acid synthesis inhibitors 🧬
🔹 Fluoroquinolones (ciprofloxacin, levofloxacin) – inhibit DNA gyrase/topoisomerase IV
🔹 Rifamycins (rifampicin) – inhibit RNA polymerase
🔹 Nitroimidazoles (metronidazole) – DNA strand breakage
Give examples of antibiotics that inhibit folate synthesis 🦠
🔹 Sulfonamides – inhibit dihydropteroate synthase
🔹 Trimethoprim – inhibits dihydrofolate reductase
💡 Often combined as co-trimoxazole
Give examples of antibiotics that disrupt cell membrane integrity ⛓️💥
🔹 Polymyxins (colistin, polymyxin B) – MDR Gram-negative, nephro/neurotoxic
🔹 Daptomycin – Gram-positive resistant, inactivated by lung surfactant
What is MIC?
Minimum Inhibitory Concentration = lowest antibiotic concentration preventing visible growth. Guides dosing to ensure drug stays above MIC for efficacy.
Time-dependent antibiotics ⏳ – definition and examples
Efficacy depends on time above MIC. Use prolonged/continuous infusions in ICU.
Examples: beta-lactams, vancomycin.
