---
title: Community-Acquired Pneumonia Treatment
description: A comprehensive clinical reference on the diagnosis and management of community-acquired pneumonia.
keywords: 
  - community-acquired pneumonia
  - antibiotic treatment
  - risk stratification
  - supportive care
category: clinical
---

## Diagnostic Criteria

Community-acquired pneumonia (CAP) is an acute infection of the pulmonary parenchyma that is acquired outside of a healthcare setting. The diagnosis of CAP is based on the presence of a new pulmonary infiltrate on chest imaging in a patient with compatible clinical symptoms, including cough, fever, and/or respiratory symptoms. 

Diagnostic criteria for CAP include:
- New pulmonary infiltrate on chest radiograph or CT scan
- Presence of at least one of the following signs/symptoms:
  - Cough
  - Fever (≥38°C or 100.4°F)
  - Pleuritic chest pain
  - Dyspnea
  - Crackles on auscultation

Specific pathogens commonly implicated in CAP include Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydia pneumoniae, and atypical organisms such as Legionella species. Viral causes, including influenza and SARS-CoV-2, should also be considered.

## Risk Stratification

Patients with CAP should be risk-stratified to guide appropriate site-of-care decisions and empiric antibiotic selection. The CURB-65 score is a validated tool that assesses 5 clinical parameters:

1. Confusion
2. Uremia (blood urea nitrogen >7 mmol/L)
3. Respiratory rate ≥30 breaths/min
4. Blood pressure: systolic <90 mmHg or diastolic ≤60 mmHg
5. Age ≥65 years

Each parameter scores 1 point, and the total CURB-65 score ranges from 0-5. Patients with a CURB-65 score of 0-1 are considered low-risk and may be suitable for outpatient management, while those with a score of ≥2 are at higher risk and may require hospital admission.

Another risk stratification tool, the Pneumonia Severity Index (PSI), incorporates additional clinical, laboratory, and demographic factors to classify patients into risk classes I-V. Patients in risk classes I-III are generally suitable for outpatient management, while those in classes IV-V warrant hospital admission.

## Empiric Antibiotic Treatment

The choice of empiric antibiotic therapy for CAP should be guided by the patient's risk factors, severity of illness, and local antimicrobial resistance patterns. The 2019 Infectious Diseases Society of America (IDSA)/American Thoracic Society (ATS) guidelines recommend the following empiric regimens:

- Outpatient, low-risk (CURB-65 0-1, PSI I-III):
  - Amoxicillin, 1 g three times daily
  - Doxycycline, 100 mg twice daily
  - Azithromycin, 500 mg daily

- Inpatient, non-severe (CURB-65 2, PSI IV):
  - Ceftriaxone, 1-2 g IV daily
  - Plus either azithromycin, 500 mg IV/oral daily, or respiratory fluoroquinolone (e.g., levofloxacin 750 mg IV/oral daily)

- Inpatient, severe (CURB-65 ≥3, PSI V):
  - Ceftriaxone, 1-2 g IV daily
  - Plus either azithromycin, 500 mg IV/oral daily, or respiratory fluoroquinolone (e.g., levofloxacin 750 mg IV/oral daily)
  - Consider addition of vancomycin or linezolid if risk factors for methicillin-resistant Staphylococcus aureus (MRSA)

Empiric antibiotic therapy should be de-escalated based on microbiological data and clinical response. The typical duration of antibiotic treatment for CAP is 5-7 days, though longer courses may be required for certain pathogens or in the setting of severe illness.

## Supportive Care

In addition to appropriate antibiotic therapy, supportive care measures are crucial in the management of CAP. These include:

- Oxygen therapy: Maintain SpO2 ≥90% (≥88% in patients with chronic obstructive pulmonary disease)
- Fluid resuscitation: Administer intravenous fluids to maintain adequate tissue perfusion
- Fever management: Use antipyretics (e.g., acetaminophen) to control fever
- Airway management: Provide mechanical ventilation for patients with respiratory failure
- Thromboprophylaxis: Administer prophylactic anticoagulation (e.g., low-molecular-weight heparin) to prevent venous thromboembolism

Patients with severe CAP may require intensive care unit (ICU) admission and advanced supportive measures, such as vasopressor support, renal replacement therapy, and extracorporeal membrane oxygenation (ECMO).

## Monitoring and Complications

Patients with CAP should be monitored closely for clinical response and potential complications, including:

- Clinical parameters: Vital signs, oxygen saturation, respiratory rate
- Laboratory tests: Complete blood count, renal and liver function, inflammatory markers (e.g., C-reactive protein, procalcitonin)
- Imaging: Repeat chest radiograph or CT scan to assess for disease progression or complications

Potential complications of CAP include:
- Respiratory failure
- Sepsis and septic shock
- Acute respiratory distress syndrome (ARDS)
- Pleural effusion or empyema
- Lung abscess
- Cardiovascular complications (e.g., myocardial infarction, arrhythmias)

Patients who fail to improve or experience clinical deterioration within 48-72 hours of initiating antibiotic therapy should be re-evaluated for potential complications or the need for escalation of care.

## Contraindications and Special Considerations

Certain patient populations require special considerations in the management of CAP:

- Penicillin allergy: Avoid beta-lactam antibiotics and use alternative agents, such as doxycycline or respiratory fluoroquinolones.
- Immunocompromised patients: Consider broader empiric coverage, including the addition of antivirals or antifungals, based on the underlying cause of immunosuppression.
- Nursing home residents: Increased risk of multidrug-resistant pathogens, such as MRSA and Pseudomonas aeruginosa, may warrant broader empiric coverage.
- Patients with prior antibiotic exposure: Increased risk of antibiotic-resistant infections may require alternative empiric regimens.

In all cases, antibiotic selection should be guided by local antimicrobial resistance patterns and adjusted based on microbiological data and clinical response.