A 60-year-old man with hypertension, hyperlipidemia, atrial fibrillation, prior transient ischemic attack, and diabetes presents with two days of cough and fever, tachycardia, tachypnea, mild hypotension, temperature 38.9 °C, oxygen saturation 87% on room air, and a right‑middle‑lobe infiltrate on chest X‑ray. What is the most appropriate diagnosis: community‑acquired pneumonia, ventilator‑associated pneumonia, hospital‑acquired pneumonia, or healthcare‑associated pneumonia?

Community-Acquired Pneumonia (CAP)

This patient has community-acquired pneumonia (CAP), defined as pneumonia acquired outside the hospital setting in a patient presenting with acute respiratory symptoms and radiographic infiltrate. 1, 2

Diagnostic Rationale

The key distinguishing feature is the timing and location of symptom onset:

• CAP develops in the community before hospital presentation, with symptoms beginning outside any healthcare facility 1, 2
• This patient presented to the ED with 2 days of symptoms (cough and fever) that clearly began at home, not in a hospital 1
• The chest X-ray showing right middle lobe infiltrate confirms pneumonic consolidation consistent with his respiratory symptoms 1, 2

Why Not the Other Diagnoses?

Hospital-Acquired Pneumonia (HAP)

• HAP requires ≥48 hours of hospitalization before pneumonia develops, and the infiltrate must not have been present or incubating at admission 3, 4
• This patient arrived at the ED with established symptoms—he did not develop them after 48 hours in the hospital 3

Ventilator-Associated Pneumonia (VAP)

• VAP is a subset of HAP occurring specifically in mechanically ventilated patients 3, 4
• This patient is not intubated or on mechanical ventilation 3

Healthcare-Associated Pneumonia (HCAP)

• The HCAP category (which included nursing home residents, recent hospitalizations, dialysis patients, etc.) has been abandoned in modern guidelines because it led to inappropriate broad-spectrum antibiotic overuse 4
• Current guidelines classify pneumonia based on where it was acquired (community vs. hospital ≥48 hours), not on patient risk factors 4, 1

Clinical Severity Assessment

This patient has severe CAP requiring hospitalization based on multiple high-risk features:

• Hypoxemia: O2 saturation 87% on room air indicates significant respiratory compromise 1, 2
• Tachypnea: Respiratory rate of 27 is markedly elevated and correlates with disease severity 1
• Multiple comorbidities: HTN, diabetes, atrial fibrillation, and prior TIA all increase pneumonia risk and mortality 2, 5
• Age 60 years with comorbidities places him in a higher-risk category 2, 5

Management Implications

For hospitalized CAP patients without ICU criteria:

• Combination therapy with IV β-lactam plus macrolide (e.g., ceftriaxone plus azithromycin) is the guideline-recommended regimen 1, 2
• First antibiotic dose within 8 hours of hospital arrival improves outcomes 1
• Blood cultures and sputum studies should be obtained but should never delay antibiotic initiation 1, 2

The distinction from HAP is critical because HAP requires broader-spectrum antibiotics covering nosocomial pathogens like Pseudomonas aeruginosa and MRSA, which would represent overtreatment in this community-acquired case 3.