Management of Community-Acquired Pneumonia (CAP)
The management of CAP is stratified by severity and treatment setting, with outpatients receiving macrolides or doxycycline, hospitalized non-ICU patients receiving β-lactam plus macrolide or respiratory fluoroquinolone monotherapy, and severe CAP/ICU patients requiring β-lactam plus either azithromycin or fluoroquinolone. 1
Initial Assessment and Severity Stratification
The first critical step is determining whether the patient has pneumonia versus an alternative diagnosis like COPD exacerbation. 2
Severity assessment drives all subsequent management decisions:
- Mild non-severe pneumonia: Suitable for outpatient management 2
- Non-severe pneumonia: Requires hospital admission 2
- Severe pneumonia: May need ICU/high dependency bed 2
The Pneumonia Severity Index (PSI) and CURB-65 criteria should guide site-of-care decisions, though physician judgment remains important, particularly for younger patients. 2, 3 Patients in PSI risk classes I, II, and III can safely be treated as outpatients absent other mitigating factors. 3
Outpatient Management
Previously Healthy Patients Without Recent Antibiotic Use
- First-line: Macrolide (azithromycin or clarithromycin) OR doxycycline 1
Patients With Comorbidities or Recent Antibiotic Use
- Preferred: Respiratory fluoroquinolone (levofloxacin or moxifloxacin) alone 1
Investigations for Outpatients
- Chest radiographs are not necessary for the majority of community-managed CAP patients 2
- Pulse oximetry should be considered for simple oxygenation assessment 2
- Microbiological investigations are not recommended routinely 2
- Sputum examination should be considered only for patients who fail empirical therapy 2
Hospitalized Non-ICU Patients
Empiric Antibiotic Therapy
Standard regimen: β-lactam (ceftriaxone 1-2 g every 24 hours, cefotaxime, or ampicillin-sulbactam) PLUS macrolide (azithromycin or clarithromycin) 1, 4
Alternative: Respiratory fluoroquinolone monotherapy 1
Initial Investigations
All hospitalized patients require: 2
- Chest radiograph
- Full blood count
- Urea, electrolytes, and liver function tests
- C-reactive protein (CRP) when available
- Oxygenation assessment
Microbiological Workup
- Blood cultures: Recommended for all hospitalized patients, preferably before antibiotics 2
- Sputum culture: For non-severe CAP patients who can expectorate purulent samples and have not received prior antibiotics 2
- Investigations should be guided by severity, epidemiological risk factors, and treatment response 2
Severe CAP/ICU Patients
Without Pseudomonas Risk Factors
Regimen: β-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS either azithromycin OR respiratory fluoroquinolone 1
With Pseudomonas Risk Factors
Regimen: Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) PLUS ciprofloxacin or levofloxacin 1
Common pitfall: Avoid reserving agents like cefepime, imipenem, meropenem, and piperacillin/tazobactam for routine use—these should be reserved for patients with documented Pseudomonas risk factors. 2
Additional Microbiological Testing for Severe CAP
- Sputum cultures are mandatory for severe CAP or treatment failure 2
- Gram stain for immediate pathogen indication 2
- Paired serological tests for all severe CAP patients 2
- Pneumococcal antigen tests if available 2
- Legionella investigations (urine antigen, culture) for all severe CAP 2
Timing and Administration
The first antibiotic dose must be administered while still in the emergency department for patients admitted through the ED. 1 This timing is critical for mortality reduction and should not be delayed. 1
Switching to Oral Therapy
Switch criteria (all must be met): 2, 1
- Hemodynamically stable
- Clinically improving
- Able to ingest medications
- Functioning gastrointestinal tract
- Afebrile (<100°F) on two occasions 8 hours apart OR other clinical features favorable even if febrile 2
Once switch criteria are met, oral therapy can be started and the patient discharged the same day if other medical and social factors permit. 2
Duration of Therapy
Minimum treatment duration: 5 days for most patients 1
Extended therapy indications: 1
- 7 days for suspected or proven MRSA or Pseudomonas aeruginosa
- 14-21 days for severe pneumonia or confirmed Legionella, staphylococcal, or gram-negative enteric bacilli
Critical pitfall: Do not treat for less than 5 days even if clinical stability is achieved earlier, and avoid routinely extending therapy beyond 8 days in responding patients without specific indications. 1
Management of Treatment Failure
Do not change initial antibiotic therapy in the first 72 hours unless marked clinical deterioration occurs. 2, 1 Up to 10% of CAP patients will not respond to initial therapy. 2
Reassessment at 72 Hours
If no improvement, evaluate for: 2, 1
- Drug-resistant or unusual pathogens
- Non-pneumonia diagnosis (inflammatory disease, pulmonary embolus)
- Pneumonia complications
- Careful requestioning about epidemiologic risk factors
- CT scan to reveal unsuspected pleural fluid collections, lung nodules, or cavitation
- Review antibiotic choice and consider complications 2
Prevention Strategies
Vaccination
- Pneumococcal vaccine (23-valent polysaccharide): All patients ≥65 years and at-risk populations 1
- Annual influenza vaccine: All at-risk patients 1
Risk Factor Modification
Smoking cessation should be promoted in all patients as it eliminates an important risk factor for CAP. 1 This counseling should occur prior to discharge if eligible. 3
Critical Pitfalls to Avoid
Antibiotic Selection Errors
- Do not rely on sputum Gram stain alone to guide initial therapy 1
- Reserve fluoroquinolones for patients with β-lactam allergies or specific indications 1
- Abandon the healthcare-associated pneumonia (HCAP) classification—only cover empirically for MRSA or Pseudomonas if locally validated risk factors are present 1
Timing Errors
- Do not delay initial antibiotic therapy 1
- Do not delay reassessment beyond 72 hours without improvement 1
- Do not continue IV therapy once oral switch criteria are met 1