MRSA Coverage
Vancomycin, Daptomycin, Linezolid, Ceftaroline
Pseudomonas Coverage
Cefepime, Piperacillin-Tazobactam, Meropenem, Ciprofloxacin
30S vs 50S Inhibitors
"Buy AT 30, CCEL at 50" (Aminoglycosides/Tetracyclines vs Chloramphenicol/Clinda/Erythro/Linezolid)
Fluoroquinolone Warnings
Tendon rupture (Achilles), QT prolongation, Aortic aneurysm rupture
Antimicrobial Mechanism of Action Matrix
Master the exact biochemical targets of board-tested antibiotic classes:
| Drug Class | Biochemical Target | Representative Agents | Key Clinical Spectrum & High-Yield Pearls |
|---|---|---|---|
| Penicillins / Cephalosporins | Transpeptidase / PBPs (inhibits cell wall cross-linking) | Penicillin, Ampicillin, Ceftriaxone, Cefepime | Bactericidal; hypersensitivity reactions (Type I IgE anaphylaxis vs Type IV rash) |
| Glycopeptides | Binds D-Ala-D-Ala terminus of cell wall peptidoglycan | Vancomycin | Gram-positives only (MRSA, C. diff oral); Red Man syndrome (histamine release; treat by slowing infusion) |
| Aminoglycosides | Binds 30S ribosomal subunit (causes misreading of mRNA) | Gentamicin, Tobramycin, Amikacin | Gram-negative aerobes; Nephrotoxicity (ATN) & Ototoxicity (contraindicated in pregnancy / myasthenia) |
| Tetracyclines | Binds 30S ribosomal subunit (blocks aminoacyl-tRNA attachment) | Doxycycline, Minocycline | Atypicals, Rickettsia, Lyme, Chlamydia; Teeth discoloration & bone growth stunting in children < 8 |
| Macrolides | Binds 50S ribosomal subunit (inhibits transpeptidation/translocation) | Azithromycin, Clarithromycin | Atypical pneumonias; QT prolongation, CYP3A4 inhibition, motilin agonist (diarrhea) |
| Lincosamides | Binds 50S ribosomal subunit | Clindamycin | Anaerobic infections above the diaphragm; MRSA; Highest risk of C. difficile colitis |
| Fluoroquinolones | Inhibits DNA Gyrase (Topoisomerase II) & Topoisomerase IV | Ciprofloxacin, Levofloxacin | Pseudomonas (Cipro), urinary and GI infections; Tendon rupture, QT prolongation |
High-Yield Empiric Clinical Regimens
Standardized first-line empiric regimens tested on Level 2/Step 2:
Community-Acquired Pneumonia (CAP) - Inpatient
Ceftriaxone + Azithromycin (or Respiratory Fluoroquinolone monotherapy: Levofloxacin / Moxifloxacin).
Hospital-Acquired / Ventilator-Associated Pneumonia (HAP/VAP)
Vancomycin (covers MRSA) PLUS Cefepime or Piperacillin-Tazobactam (covers Pseudomonas).
Bacterial Meningitis (Adults < 50)
Vancomycin + Ceftriaxone + Dexamethasone. Add Ampicillin if age > 50 or immunocompromised to cover Listeria monocytogenes.
Acute Pyelonephritis
Outpatient: Ciprofloxacin or Ceftriaxone. Inpatient: IV Ceftriaxone or Ciprofloxacin.
COMLEX / OMM Integration
NBOME High-Yield Correlate
Lymphatic Pumps & Immune Mobilization
- Thoracic Pump Technique: Increases lymphatic flow through the thoracic duct, enhancing delivery of immunoglobulins and white blood cells into systemic circulation during infection.
- Splenic Pump: Enhances release of opsonic antibodies and reticuloendothelial clearance in non-splenomegalic infections.
Board Traps & Common Distractors
- Trap: Using Daptomycin for pulmonary infections (MRSA pneumonia). Daptomycin is inactivated by pulmonary surfactant and completely ineffective in pneumonia! Use Vancomycin or Linezolid.
- Trap: Administering Ceftriaxone in neonates (< 28 days old). Ceftriaxone displaces bilirubin from albumin, causing kernicterus, and can precipitate with calcium. Use Cefotaxime instead in neonates.