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Difficulty: HardPediatric Respiratory Disorders

An 8-year-old girl is admitted to the pediatric ward with a 6-day history of worsening productive cough, low-grade fever, and increasing shortness of breath. She has a past medical history of recurrent sinopulmonary infections, nasal polyps, and chronic malabsorption requiring daily pancreatic enzyme supplementation. Her immunizations, including the annual influenza vaccine, are up to date. On admission, her temperature is 38.5°C (101.3°F), blood pressure is 105/65 mmHg, heart rate is 118/min, and respiratory rate is 28/min. Pulse oximetry shows 92% on room air. Physical examination reveals digital clubbing, an increased anteroposterior chest diameter, and coarse crackles over the bilateral upper lung fields. Sputum analysis is performed, and the Gram stain demonstrates abundant neutrophils and Gram-negative bacilli that are oxidase-positive and non-lactose fermenting. Which of the following is the most appropriate antimicrobial regimen for this patient's acute respiratory exacerbation?

  1. A
    Intravenous ceftriaxone and azithromycin
  2. B
    Intravenous vancomycin and oral oseltamivir
  3. Intravenous cefepime and tobramycinAnswer
  4. D
    Oral amoxicillin and scheduled nebulized albuterol
  5. E
    Intravenous ampicillin and gentamicin

Answer

Intravenous cefepime and tobramycin
This patient's clinical presentation of recurrent sinopulmonary infections, nasal polyps, and pancreatic insufficiency strongly indicates a diagnosis of cystic fibrosis (CF). She is currently experiencing an acute pulmonary exacerbation. The sputum Gram stain reveals Gram-negative, oxidase-positive, non-lactose fermenting bacilli, which is highly specific for Pseudomonas aeruginosa. P. aeruginosa is the most common cause of pulmonary exacerbations in CF patients after early childhood. Because it forms biofilms in the thick mucus of CF airways and readily develops resistance, standard of care for a severe exacerbation requires dual antibiotic therapy. The chosen regimen must include two antipseudomonal agents with different mechanisms of action. The combination of an antipseudomonal beta-lactam (such as cefepime, ceftazidime, or piperacillin-tazobactam) and an aminoglycoside (such as tobramycin) provides the necessary synergistic double coverage to effectively treat the infection and prevent resistance.

Step-by-Step Solution

1
Identify the patient's underlying systemic disease based on the clinical presentation.
The patient has cystic fibrosis (CF).
The history of recurrent sinopulmonary infections, nasal polyps, chronic malabsorption (requiring pancreatic enzymes), and digital clubbing is classic for cystic fibrosis.
2
Interpret the sputum Gram stain to identify the causative organism of the current exacerbation.
The pathogen is Pseudomonas aeruginosa.
The Gram stain describes Gram-negative bacilli that are oxidase-positive and non-lactose fermenting, which are the hallmark microbiological characteristics of Pseudomonas aeruginosa.
3
Select the appropriate pharmacologic intervention for a CF pulmonary exacerbation caused by this pathogen.
Intravenous cefepime and tobramycin.
Due to the thick mucus in CF lungs and the high risk of antibiotic resistance, an acute exacerbation involving P. aeruginosa must be treated with two antipseudomonal antibiotics from different classes. Cefepime (an antipseudomonal cephalosporin) and tobramycin (an aminoglycoside) fulfill this requirement.

Key Concept

Management of Cystic Fibrosis Pulmonary Exacerbations
Estimated Time:1m 30s
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Topics

Pediatric Respiratory Disorders

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