Community-Acquired Pneumonia: Diagnosis and Treatment
Micro-brief created with inScope · Clinically reviewed by Yasmine Abbey, MD, MSc · Last reviewed:
Educational summary for clinicians. Not medical advice — verify against primary sources, your clinical judgment, and institutional protocols.
Bottom line
For community-acquired pneumonia, confirm an infiltrate on chest imaging and start empiric antibiotics promptly, chosen by the 2019 ATS/IDSA severity strata; give supplemental oxygen to keep SpO2 ≥ 92%, and adjust therapy once microbiology returns.
Cover MRSA or Pseudomonas empirically only when there is prior isolation within the past year or recent IV antibiotics — and send blood and sputum cultures first, de-escalating at 48 hours if cultures are negative. Treat for at least 5 days, continuing until the patient is clinically stable and afebrile for ≥ 48 hours.
Initial workup
- Take a thorough history (recent antibiotics, comorbid lung disease, residence, aspiration risk) and a focused exam for severity signs.
- Confirm an infiltrate with a chest radiograph, or CT when the plain film is equivocal.
- Baseline labs: CBC, BMP, and a hepatic panel; pulse oximetry or ABG if hypoxemic; inflammatory markers (e.g., CRP) are permitted but not required.
- Send blood and sputum cultures before the first antibiotic dose if there is prior MRSA or Pseudomonas isolation within the past year or recent IV antibiotic exposure.
Acute management
- Start empiric IV antibiotics within the first hospital hours according to the 2019 ATS/IDSA severity strata, and adjust once microbiology is available.
- Supplemental oxygen to keep SpO2 ≥ 92% (higher for an underlying chronic hypoxemic condition).
- IV fluids for sepsis-induced hypotension; vasopressors and ICU consultation if shock develops.
- Early mobilization, incentive spirometry, and VTE prophylaxis as indicated.
Inpatient and longitudinal management
- Reassess clinically each day; narrow or discontinue antimicrobials at 48–72 hours if cultures are negative and the patient is improving.
- Convert to an oral regimen once hemodynamically stable, afebrile for 24 hours, and able to take oral medication.
- A typical total course is at least 5 days, continued until the patient is afebrile for ≥ 48 hours with no more than one CAP-associated instability criterion.
- Address modifiable risks — smoking cessation and pneumococcal and influenza vaccination before discharge.
Monitoring and disposition
- Vitals, mental status, and oxygenation every 4 hours initially; watch for deterioration within the first 48 hours.
- Evaluate daily for the switch to oral therapy and discharge readiness (stable vitals, oral intake, SaO2 ≥ 90% on room air or baseline).
- Arrange outpatient follow-up in 1 week, and a repeat chest radiograph in 6–8 weeks if there are risk factors for underlying malignancy or non-resolving symptoms.
Escalate care if
- CURB-65 ≥ 3, PSI class IV/V, a need for vasopressors, or invasive/non-invasive ventilation — escalate to ICU per the ATS/IDSA pathway.
- Risk factors or cultures positive for MRSA or Pseudomonas aeruginosa — broaden empiric coverage and involve Infectious Diseases, de-escalating once sensitivities are known.
Duration
A minimum of 5 days of total therapy, extended until clinically stable (afebrile for ≥ 48 hours with normalizing vitals).
Caveats
- Manage patients who present with septic shock or a need for mechanical ventilation in an ICU setting.
- Account for beta-lactam allergy and immunocompromise when selecting empiric therapy.
References
- Diagnosis and Treatment of Adults with Community-acquired Pneumonia (ATS/IDSA). Am J Respir Crit Care Med. (2019) · Primary guideline“Diagnosis and Treatment of Adults with Community-acquired Pneumonia (ATS/IDSA).”
- Community-Acquired Pneumonia Clinical Pathway. · Primary guideline“The flowchart indicates actions to take and decision points in the clinical workflow for diagnosis and treatment of patients with suspected community-acquired pneumonia.”
- Diagnosis and Treatment of Adults with Community-acquired Pneumonia — Executive Summary. · Primary guideline“Prior identification of MRSA or P. aeruginosa in the respiratory tract within the prior year predicts a very high risk ... sufficient indications to recommend blood and sputum cultures and empiric therapy for these pathogens ... with deescalation at 48 hours if cultures are negative.”