Pertussis Evaluation and Treatment
This patient requires immediate nasopharyngeal culture for pertussis and empiric macrolide antibiotic therapy should be started without waiting for results, given the classic presentation of >2 weeks cough with post-tussive vomiting and paroxysms. 1, 2
Why This is Pertussis Until Proven Otherwise
The clinical picture strongly suggests Bordetella pertussis infection:
- Cough duration >2 weeks with paroxysmal episodes 1
- Post-tussive vomiting (emesis after coughing paroxysms) 1, 3
- Initial mild URI symptoms that have now improved - this represents the transition from the catarrhal phase to the paroxysmal phase 1
The American College of Chest Physicians states that when these features are present, pertussis should be diagnosed unless another cause is proven. 1
Immediate Diagnostic Steps
Obtain nasopharyngeal aspirate or Dacron swab for culture immediately - this is the only certain way to confirm B. pertussis, though sensitivity is only 25-50%. 1
Do not delay treatment while awaiting culture results - early therapy is critical even though the patient is already 2+ weeks into illness. 1
PCR testing is available but not routinely recommended due to lack of standardized, validated techniques. 1
Treatment Protocol
Macrolide Antibiotic Therapy (Start Immediately)
Erythromycin 1-2 g per day in adults for 2 weeks is the recommended first-line treatment. 1
Alternative macrolides (azithromycin or clarithromycin) are acceptable and better tolerated. 3
Trimethoprim/sulfamethoxazole should be used only when macrolides cannot be given. 1
Critical Timing Considerations
While therapy is most effective during the catarrhal phase (first 2 weeks), treatment should still be initiated even at >2 weeks because it will:
- Rapidly clear B. pertussis from the nasopharynx 1
- Decrease coughing paroxysms and complications 1
- Prevent transmission to others 1
Isolation Requirements
The patient must be isolated at home and away from work/school for 5 days after starting antibiotic therapy. 1
If Pertussis is Ruled Out: Post-Infectious Cough Management
If cultures are negative and pertussis is excluded, this becomes post-infectious cough (defined as 3-8 weeks duration following acute respiratory infection). 1
Stepwise Treatment Algorithm
First-line: Inhaled ipratropium bromide - this has the strongest evidence for attenuating post-infectious cough in controlled trials. 1, 2, 3
Second-line: Inhaled corticosteroids - consider when cough adversely affects quality of life or persists despite ipratropium. 1, 2
For severe paroxysms: Oral prednisone 30-40 mg daily for a short, finite period after ruling out upper airway cough syndrome, asthma, and GERD. 1, 2
Central-acting antitussives (dextromethorphan 60 mg or codeine) - consider when other treatments fail, though dextromethorphan is preferred due to fewer side effects. 2, 4
What NOT to Do
Do not prescribe antibiotics for post-infectious viral cough - they provide no benefit (reducing cough by only half a day), contribute to antibiotic resistance, and cause adverse effects including allergic reactions, nausea, vomiting, and C. difficile infection. 1, 2, 5, 6
This prohibition does NOT apply to confirmed or suspected pertussis, which absolutely requires macrolide therapy. 1
Red Flags Requiring Further Evaluation
If cough persists beyond 8 weeks total duration, reclassify as chronic cough and systematically evaluate for:
- Upper airway cough syndrome 1, 5
- Asthma or eosinophilic bronchitis 1, 5
- Gastroesophageal reflux disease 1, 5
Obtain chest radiograph if patient develops:
- Tachypnea (≥24 breaths/min), tachycardia (≥100 bpm), or fever (≥38°C) 5
- Focal lung findings, asymmetrical breath sounds, or signs of consolidation 5, 6
Common Pitfall to Avoid
The most critical error would be dismissing this as simple post-viral cough and missing pertussis. Post-tussive vomiting with paroxysmal cough at >2 weeks duration is pertussis until proven otherwise, regardless of vaccination status, as breakthrough infections occur. 1, 3