Which antibiotic should be initiated for severe leptospirosis (Weil’s disease) in a 35‑year‑old man who developed fever and calf pain 5 days after wading in flood water and now presents with jaundice and oliguria, according to the 2010 Clinical Practice Guidelines?

Antibiotic Treatment for Severe Leptospirosis (Weil's Disease)

Ceftriaxone 1–2 g IV q24h (option c) should be initiated immediately for this patient with severe leptospirosis presenting with jaundice and oliguria. 1

Rationale for Ceftriaxone as First-Line Treatment

• Ceftriaxone 2g IV daily for 7 days is the preferred antibiotic for severe leptospirosis due to its superior efficacy, once-daily administration convenience, and better adverse effect profile compared to penicillin. 1

• The Infectious Diseases Society of America specifically recommends ceftriaxone as the treatment of choice for severe disease over other options. 1

• Treatment must be initiated immediately upon clinical suspicion without waiting for serological confirmation, as each hour of delay increases mortality. 1, 2

Why Other Options Are Suboptimal

• Doxycycline 100mg q6h (option a) is incorrect for two reasons: First, doxycycline is reserved for mild-to-moderate disease, not severe presentations. 2 Second, the correct dosing for mild disease is 100mg twice daily (q12h), not q6h. 2

• Ampicillin 1.5g q6h (option b) is not the standard recommendation. While penicillin G 1.5 million units IV q6h is an acceptable alternative for severe disease 1, ampicillin at this dose is not the guideline-recommended regimen.

• Benzathine Penicillin G 2.4M units IV q24h (option d) is incorrect because benzathine penicillin is a long-acting intramuscular formulation used for conditions like syphilis, not for acute severe infections requiring immediate bactericidal activity. 1

Defining Severe Disease in This Case

This patient meets multiple criteria for severe leptospirosis (Weil's disease):

• Jaundice with hepatorenal syndrome is a hallmark of severe disease. 1, 3

• Oliguria indicating acute kidney injury is one component of the classic triad. 1

• The classic triad includes jaundice, renal failure, and hemorrhagic manifestations, though not all three need be present simultaneously. 1

• Exposure history (wading in flood water 5 days prior) with subsequent fever and calf pain (characteristic myalgias) followed by progression to jaundice and oliguria is the typical clinical course. 3, 4

Critical Management Algorithm

Step 1: Immediate Antibiotic Initiation

• Start ceftriaxone 2g IV daily within the first hour of recognition without waiting for laboratory confirmation. 1

• Obtain blood cultures before antibiotics only if this causes no significant delay (<45 minutes), ideally within the first 5 days of illness. 1

• The standard antibiotic course is 7 days, but may need extension to 10 days in patients with slow clinical response. 1

Step 2: Aggressive Supportive Care

• Administer aggressive IV fluid resuscitation with isotonic crystalloid solution up to 60 ml/kg in three boluses of 20 ml/kg, reevaluating after each bolus for signs of shock. 1

• Continuously monitor for development of crepitations indicating fluid overload or deteriorated cardiac function during resuscitation. 1

• Consult ICU early if the patient requires repeated fluid boluses or shows signs of circulatory failure. 1

Step 3: Renal Support

• Initiate hemodialysis or continuous renal replacement therapy for severe acute kidney injury with oliguria. 1, 5

• Use continuous therapies to facilitate fluid balance management in hemodynamically unstable patients. 1

Step 4: Monitor for Complications

• Expect clinical improvement within 3 days of starting antibiotics. 1, 2

• Avoid aspirin due to risk of hemorrhagic complications. 1

• Consider methylprednisolone 0.5-1.0 mg/kg IV daily for 1-2 weeks if respiratory complications develop. 1, 2

Common Pitfalls to Avoid

• Do not wait for serological confirmation before initiating antibiotics, as serology is often negative in the first week and delay increases mortality. 1, 2

• Do not underestimate disease severity based on modest transaminase elevations—markedly elevated bilirubin with disproportionately mild liver enzyme elevation is characteristic of severe leptospirosis. 6

• Do not discontinue antibiotics early despite clinical improvement; complete the full 7-day course. 1, 2

• Do not confuse leptospirosis with viral hepatitis in patients presenting with fever and jaundice—the exposure history and clinical pattern should guide diagnosis. 1, 2

• Do not use oral antibiotics for severe disease—IV therapy is mandatory for patients with jaundice, oliguria, or other signs of organ dysfunction. 1