What is the diagnosis and treatment for a patient with fever, productive cough, and new onset infiltrates on chest x-ray?

Diagnosis: Community-Acquired Pneumonia (CAP)

This patient has community-acquired pneumonia, confirmed by the classic triad of fever (38°C), productive cough, and new infiltrates on chest x-ray. 1, 2

Immediate Diagnostic Confirmation

The combination of fever, productive cough, and radiographic infiltrates establishes the diagnosis of pneumonia without requiring additional confirmatory testing before initiating treatment. 1, 2 The presence of new pulmonary infiltrates on chest x-ray is the most reliable diagnostic finding, present in 75-90% of suspected pneumonia cases. 3

Severity Assessment (Must Be Done Immediately)

Use CURB-65 or CRB-65 scoring immediately to determine treatment setting (outpatient vs. inpatient vs. ICU). 1 This severity stratification directly impacts mortality and must guide your initial management decisions.

Key severity indicators to assess:

• Respiratory rate ≥25 breaths/min suggests impending respiratory failure 3
• Oxygen saturation <90% on pulse oximetry indicates severe disease 3
• Mental status changes, hypotension, or uremia (components of CURB-65) 1

Initial Management Steps

For Hospitalized Non-ICU Patients:

Start empiric antibiotics immediately (within the first hour if possible) with β-lactam (ceftriaxone or cefotaxime) PLUS a macrolide (azithromycin). 1, 4 This combination therapy should be continued for a minimum of 3 days. 4

For ICU Patients:

Use antipseudomonal β-lactam (cefepime, piperacillin/tazobactam, imipenem, or meropenem) PLUS either an antipseudomonal fluoroquinolone OR a macrolide plus an aminoglycoside. 1

Essential Diagnostic Studies

Before starting antibiotics (if feasible without delaying treatment):

• Two sets of blood cultures (one peripheral, one from any vascular access if present) 3
• Sputum Gram stain and culture if good quality specimen available (>25 PMNs and <10 epithelial cells per low-power field) 2
• COVID-19 and influenza testing when these viruses are circulating in the community, as positive results alter treatment 4

Common pitfall: Do not delay antibiotic administration to obtain diagnostic specimens. Blood cultures have <25% sensitivity but high specificity when positive. 2 Even with extensive testing, no pathogen is identified in up to 62% of CAP cases. 2, 4

Special Considerations

If Influenza Season or Suspected Viral Component:

Add oseltamivir if influenza is suspected or confirmed. 1 Up to 40% of hospitalized CAP patients have viral etiologies. 4

If Bilateral Infiltrates:

Bilateral hazy infiltrates may indicate more severe disease or alternative diagnoses. 1 Consider:

• Cardiac failure (check BNP, echocardiogram if indicated) 1
• Pulmonary embolism (assess Wells criteria) 1
• Atypical pathogens (already covered by macrolide in combination therapy) 4

Monitoring Response:

Clinical improvement should be apparent within 48-72 hours. 1 Do not change antibiotics during this period unless progressive deterioration occurs or microbiologic data dictates a change. 1

Treatment Duration

Continue antibiotics for minimum 5 days, and until the patient is afebrile for 48-72 hours with no more than one sign of clinical instability. 1 Recent evidence supports 3-5 days if good clinical improvement by day 2-3. 4, 5

ICU Transfer Criteria

Transfer to ICU if any of the following develop:

• Persistent hypoxia (PaO₂ <60 mmHg) despite maximal oxygen 3, 1
• Progressive hypercapnia or severe acidosis (pH <7.26) 1
• Septic shock 1
• Need for mechanical ventilation 1

Key Clinical Pearls

• Streptococcus pneumoniae remains the most common bacterial pathogen (15% of identified cases), though macrolide resistance is increasing. 4, 5
• Switch from IV to oral antibiotics when symptoms improve, patient is afebrile, and can tolerate oral intake. 1
• Procalcitonin levels can guide antibiotic duration as an adjunct to clinical judgment. 5
• Systemic corticosteroids within 24 hours may reduce 28-day mortality in severe CAP. 4