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Difficulty: EasyInfectious Diseases

A 42-year-old man presents to the urgent care clinic with a 2-day history of increasing redness, swelling, and pain on his right lower leg. He denies fevers, chills, or recent trauma, though he reports chronic itching between his toes. He has no significant past medical history and takes no medications. His temperature is 37.0°C (98.6°F), blood pressure is 118/76 mmHg, pulse is 72/min, and respiratory rate is 14/min. Physical examination of the right lower extremity reveals a warm, tender, and erythematous plaque with indistinct borders extending from the ankle to the mid-calf. There is no purulent exudate, ulceration, or fluctuance. Examination of the feet shows fissuring and maceration between the fourth and fifth digits. Which of the following is the most appropriate empiric treatment for this patient?

  1. A
    Oral amoxicillin-clavulanate
  2. Oral cephalexinAnswer
  3. C
    Oral ciprofloxacin
  4. D
    Intravenous vancomycin
  5. E
    Oral trimethoprim-sulfamethoxazole

Answer

Oral cephalexin is the most appropriate initial therapy for this patient.
This patient presents with mild, uncomplicated, non-purulent cellulitis, as evidenced by a spreading area of warm, tender erythema without exudate or fluctuance. The fissuring from tinea pedis likely served as the portal of entry for bacteria. Non-purulent cellulitis is primarily caused by beta-hemolytic streptococci (most notably Group A Streptococcus) and, less commonly, methicillin-susceptible Staphylococcus aureus (MSSA). Because the patient is hemodynamically stable and lacks systemic signs of infection (e.g., fever, tachycardia), outpatient oral therapy is appropriate. Good antibiotic stewardship dictates using the narrowest spectrum agent effective against the likely pathogens. An oral first-generation cephalosporin (such as cephalexin) or a penicillinase-resistant penicillin (such as dicloxacillin) is the gold standard empiric therapy for this condition.

Step-by-Step Solution

1
Identify the clinical syndrome.
The patient has unilateral erythema, warmth, and swelling without fluctuance or purulence.
These findings are classic for mild, non-purulent cellulitis. The tinea pedis provides a portal of entry for skin flora.
2
Determine the most likely causative organisms.
Beta-hemolytic streptococci (e.g., Group A Streptococcus) and methicillin-susceptible Staphylococcus aureus (MSSA).
Non-purulent cellulitis is overwhelmingly caused by streptococci, whereas purulent cellulitis (with abscess or exudate) is more frequently caused by Staphylococcus aureus (including MRSA).
3
Select the appropriate pharmacotherapy based on antibiotic stewardship principles.
A narrow-spectrum oral beta-lactam such as cephalexin, penicillin, or dicloxacillin.
The patient is hemodynamically stable, has no signs of systemic toxicity, and lacks risk factors for MRSA. Broad-spectrum or intravenous antibiotics are unnecessary and inappropriate.

Key Concept

Empiric treatment for mild, non-purulent cellulitis should target beta-hemolytic streptococci and MSSA using narrow-spectrum oral agents like cephalexin.
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Topics

Infectious Diseases

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