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Difficulty: MediumPediatric Respiratory Disorders

A 6-week-old boy is evaluated in the clinic for a worsening, repetitive cough that started one week ago. His mother reports that the cough comes in rapid, machine-gun-like bursts. The infant has not had a fever and continues to breastfeed well, although he occasionally spits up after coughing. Pregnancy and vaginal delivery were uncomplicated, though the mother received limited prenatal care. At 2 weeks of age, the infant had watery, red eyes that resolved over several days without specific treatment. Vital signs are temperature 37.0°C (98.6°F), heart rate 145/min, and respiratory rate 55/min. Pulse oximetry is 97% on room air. Physical examination reveals an alert infant. Lung auscultation demonstrates bilateral scattered crackles with no prominent wheezing. A chest radiograph shows bilateral symmetrical interstitial infiltrates and hyperinflation. Laboratory studies reveal a leukocyte count of 12,000/mm³ with 12% eosinophils. Which of the following is the most appropriate pharmacotherapy for this patient?

  1. Oral azithromycinAnswer
  2. B
    Nebulized albuterol
  3. C
    Intravenous ampicillin and cefotaxime
  4. D
    Oral amoxicillin
  5. E
    Inhaled budesonide

Answer

The correct answer is oral azithromycin, which targets the intracellular bacterium Chlamydia trachomatis.
Oral azithromycin is the correct choice. This infant presents with the classic triad for Chlamydia trachomatis pneumonia: an afebrile presentation, a staccato (machine-gun-like) cough, and peripheral eosinophilia. The history of conjunctivitis at 2 weeks of life (inclusion conjunctivitis) and the mother's limited prenatal care (increasing the risk of untreated maternal cervical infection) further support this diagnosis. Because Chlamydia trachomatis is an obligate intracellular organism lacking a typical peptidoglycan cell wall, it does not respond to beta-lactam antibiotics. Macrolides, such as oral azithromycin, are the treatment of choice.

Step-by-Step Solution

1
Analyze the patient's demographic and clinical presentation.
A 6-week-old afebrile infant with a staccato cough, tachypnea, and a history of limited maternal prenatal care.
Identifying the classic timeline and symptom profile is crucial for distinguishing between typical and atypical neonatal pneumonias.
2
Evaluate the patient's medical history and laboratory findings.
The history of conjunctivitis at 2 weeks of age and the presence of peripheral eosinophilia (12%) strongly indicate a specific pathogen.
These findings are classic hallmarks of Chlamydia trachomatis infection acquired during vaginal delivery.
3
Determine the optimal pharmacotherapy.
Select a macrolide antibiotic.
Chlamydia trachomatis is an obligate intracellular organism that does not have a typical peptidoglycan cell wall, making beta-lactams ineffective. Oral azithromycin is the preferred treatment.

Key Concept

Chlamydia trachomatis pneumonia presents in infants aged 1 to 3 months with an afebrile staccato cough, peripheral eosinophilia, and a history of inclusion conjunctivitis. The treatment of choice is an oral macrolide, such as azithromycin.
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Topics

Pediatric Respiratory Disorders

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