What's the next step for an army recruit with a dry cough, diarrhea, and polyuria who had partial relief with a Z-pack (azithromycin)?

Management of Army Recruit with Dry Cough, Diarrhea, and Polyuria

The next step for this army recruit should be testing for nontuberculous mycobacterial infection (NTM), particularly Mycobacterium avium complex (MAC), as this is the most likely diagnosis given the constellation of symptoms and partial response to azithromycin.

Clinical Assessment of Current Presentation

The patient presents with three key symptoms that suggest a systemic infection rather than isolated respiratory illness:

1. Dry cough - Persistent despite partial improvement with azithromycin
2. Diarrhea - Concurrent with respiratory symptoms
3. Polyuria - Suggests systemic involvement or metabolic disturbance

The partial response to azithromycin (Z-pack) is particularly telling, as this suggests an atypical infection that is partially sensitive to macrolides but requires longer treatment duration.

Diagnostic Approach

Step 1: Rule Out COVID-19

• Given the military setting and respiratory symptoms, COVID-19 testing should be performed first 1
• Obtain chest imaging (X-ray or CT) to assess for infiltrates or bronchiectasis

Step 2: Test for Nontuberculous Mycobacteria

• Collect sputum samples for acid-fast bacilli (AFB) staining and culture
• Request specific testing for Mycobacterium avium complex (MAC)
• Consider bronchoscopy with bronchoalveolar lavage if sputum samples are non-diagnostic

Step 3: Additional Testing

• Complete blood count to assess for lymphopenia
• Comprehensive metabolic panel to evaluate renal function (given polyuria)
• Stool studies for enteric pathogens
• Urinalysis to evaluate polyuria

Treatment Recommendations

Initial Management

1. Extend Azithromycin Treatment

   • Continue azithromycin at 500mg daily for 3 days, then 250mg daily (if MAC is suspected) 1, 2
   • The partial response to the initial Z-pack suggests sensitivity to macrolides

2. Add Symptomatic Treatment

   • For dry cough: Dextromethorphan 30mg every 6-8 hours (not exceeding 120mg/24 hours) 3, 4
   • For diarrhea: Consider adding loperamide to azithromycin as this combination has shown better efficacy than azithromycin alone 5

Definitive Treatment (If MAC is confirmed)

If MAC infection is confirmed, implement a multidrug regimen:

• Clarithromycin (500mg twice daily) or azithromycin (250mg daily)
• Ethambutol (15mg/kg daily)
• Rifampin (600mg daily) or rifabutin (300mg daily) 1

Special Considerations for Military Personnel

1. Infection Control

   • Consider isolation until infectious etiology is determined
   • Implement appropriate precautions based on military protocols 1

2. Duty Status

   • Recommend limited duty until diagnosis is established and treatment response is observed
   • Hydration status must be monitored given diarrhea and polyuria

Potential Pitfalls and Caveats

1. Antibiotic Overuse

   • Routine antibiotics are not recommended for uncomplicated acute bronchitis 1
   • However, the combination of symptoms and partial response to azithromycin suggests an atypical infection requiring targeted therapy

2. Medication Toxicity

   • Monitor for azithromycin side effects, especially with prolonged use 1, 2
   • Macrolide toxicity is dose and serum-level related, with gastrointestinal symptoms being most common

3. Diagnostic Challenges

   • NTM infections can be difficult to diagnose and often require multiple sputum samples
   • False negatives are common with standard testing methods

4. Polyuria Evaluation

   • Polyuria (>3L urine output/24h) requires specific evaluation 6
   • May be related to infection-induced diabetes insipidus or other metabolic disturbances

The combination of dry cough, diarrhea, and polyuria with partial response to azithromycin strongly suggests an atypical infection such as MAC. Proper diagnosis and extended antimicrobial therapy are essential for preventing progression to chronic disease and ensuring return to full military duty.