Morbid Obesity with Cellulitis and Possible Bacteraemia
Scenario:
A 52‑year‑old man with a body mass index of 45 kg/m² presents with a 24‑hour history of rapidly spreading erythema and tenderness over his right lower leg. He is mildly febrile (39 °C) and tachycardic (110 bpm). There are no underlying chronic illnesses. Blood cultures are drawn given concern for early bacteraemia, and you plan admission for IV therapy covering Streptococcus spp. and MRSA.
Question:
Which empiric IV antibiotic is most appropriate for this patient?
A) Vancomycin
B) Daptomycin
C) Linezolid
D) Ceftaroline
E) Clindamycin
✅ Preferred Answer: B) Daptomycin
📘 Mini‑Lesson & Explanation
1. Why Daptomycin?
Bactericidal against MRSA and Streptococcus spp., suitable for suspected bacteraemia.
Exhibits linear pharmacokinetics in obesity, so dosing by total body weight yields predictable levels without excessively large loading doses.
Low nephrotoxicity compared to vancomycin, making it a safer choice in high‑weight individuals.
Once‑daily dosing simplifies administration and monitoring.
2. Why Not Vancomycin?
Requires high trough targets (15–20 mg/L) for MRSA → elevated risk of acute kidney injury in obese patients.
Complex dosing and frequent level checks can delay reaching therapeutic concentrations.
3. The Role of Ceftaroline
Excellent bactericidal activity against MRSA and Streptococcus spp. and is often used as salvage therapy in persistent bacteraemia when other agents fail.
Also covers certain Gram‑negative rods, but this extra spectrum is generally unnecessary in uncomplicated cellulitis and may promote resistance.
Cost considerations: significantly more expensive than alternatives such as daptomycin.
4. Why Not Linezolid?
Bacteriostatic against staphylococci and streptococci, less ideal for bloodstream infections.
Risk of thrombocytopenia with prolonged courses.
5. Why Not Clindamycin?
Good tissue penetration but unreliable MRSA coverage and also bacteriostatic, making it unsuitable when bacteraemia is suspected.
💡 Teaching Pearls
Obesity & PK/PD: Choose agents with predictable kinetics in high‑BMI patients—daptomycin is ideal.
Bactericidal vs. Bacteriostatic: For suspected bloodstream infection, always favour bactericidal antibiotics.
Spectrum Stewardship: Avoid excessive Gram‑negative coverage unless clearly indicated—unnecessary broad coverage drives resistance and increases cost.
No comments:
Post a Comment