What is the management approach for a patient with community-acquired pneumonia, considering factors such as age, medical history, and disease severity?

Management of Community-Acquired Pneumonia

For hospitalized non-ICU patients with community-acquired pneumonia, use ceftriaxone 1-2 g IV daily plus azithromycin 500 mg daily for a minimum of 5 days, transitioning to oral therapy when clinically stable. 1

Initial Assessment and Site-of-Care Decision

Severity stratification determines management location and antibiotic selection. Use validated tools to guide admission decisions 2:

• Outpatient criteria: Previously healthy adults without comorbidities, stable vital signs, and ability to maintain oral intake 2, 1
• Hospitalization indicators: Age ≥65 years, multilobar infiltrates, respiratory rate >24, systolic BP <90 mmHg, oxygen saturation <90%, or inability to take oral medications 2, 3
• ICU admission criteria: Severe respiratory failure requiring mechanical ventilation, septic shock requiring vasopressors, or rapid clinical deterioration within 72 hours 2

Risk factors increasing mortality include COPD, renal insufficiency, chronic heart failure, diabetes, malignancy, chronic liver disease, and institutionalization in patients >60 years 2

Outpatient Treatment

For previously healthy adults without comorbidities, amoxicillin 1 g orally three times daily for 5-7 days is first-line therapy. 1, 4

• Alternative: Doxycycline 100 mg orally twice daily 1, 5
• Macrolides (azithromycin 500 mg day 1, then 250 mg daily; or clarithromycin 500 mg twice daily) should only be used when local pneumococcal macrolide resistance is documented <25% 1, 5

For patients with comorbidities (COPD, diabetes, chronic heart/liver/renal disease, malignancy, or recent antibiotic use within 3 months):

• Combination therapy: Amoxicillin-clavulanate 875/125 mg twice daily PLUS azithromycin 500 mg day 1, then 250 mg daily for days 2-5 1
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 1, 5

Hospitalized Non-ICU Patients

Two equally effective regimens exist with strong evidence 1, 6:

1. β-lactam plus macrolide: Ceftriaxone 1-2 g IV daily PLUS azithromycin 500 mg daily 1, 6

   • Alternative β-lactams: Cefotaxime 1-2 g IV every 8 hours or ampicillin-sulbactam 3 g IV every 6 hours 2, 1

2. Respiratory fluoroquinolone monotherapy: Levofloxacin 750 mg IV daily OR moxifloxacin 400 mg IV daily 1, 5

For penicillin-allergic patients: Use respiratory fluoroquinolone as preferred alternative 2, 1

Severe CAP Requiring ICU Admission

Combination therapy is mandatory for all ICU patients—monotherapy is inadequate for severe disease. 2, 1

Standard regimen: Ceftriaxone 2 g IV daily (or cefotaxime 1-2 g IV every 8 hours or ampicillin-sulbactam 3 g IV every 6 hours) PLUS azithromycin 500 mg IV daily OR respiratory fluoroquinolone (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily) 2, 1, 6

The most common lethal pathogens in ICU patients are S. pneumoniae, P. aeruginosa, and L. pneumophila, with the latter two frequently requiring mechanical ventilation 2

Special Pathogen Coverage

Add antipseudomonal coverage ONLY when specific risk factors are present 1, 5:

• Structural lung disease (bronchiectasis, cystic fibrosis)
• Recent hospitalization with IV antibiotics within 90 days
• Prior respiratory isolation of P. aeruginosa
• Prolonged broad-spectrum antibiotic use (≥7 days within past month) 2

Antipseudomonal regimen: Antipseudomonal β-lactam (piperacillin-tazobactam 4.5 g IV every 6 hours, cefepime 2 g IV every 8 hours, imipenem, or meropenem) PLUS ciprofloxacin 400 mg IV every 8 hours OR levofloxacin 750 mg IV daily PLUS aminoglycoside (gentamicin or tobramycin 5-7 mg/kg IV daily) PLUS azithromycin 2, 1

Add MRSA coverage ONLY when risk factors are present 1, 5:

• Prior MRSA infection or colonization
• Recent hospitalization with IV antibiotics
• Post-influenza pneumonia
• Cavitary infiltrates on imaging

MRSA regimen: Add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) OR linezolid 600 mg IV every 12 hours to base regimen 2, 1

Duration of Therapy

Treat for a minimum of 5 days AND until the patient is afebrile for 48-72 hours with no more than one sign of clinical instability. 1, 4, 6

• Typical duration for uncomplicated CAP: 5-7 days 1, 5
• Extended duration (14-21 days) required for Legionella pneumophila, Staphylococcus aureus, or Gram-negative enteric bacilli 2, 1
• Severe microbiologically undefined pneumonia: 10 days 2

Clinical stability criteria include: temperature ≤37.8°C, heart rate ≤100 beats/min, respiratory rate ≤24 breaths/min, systolic BP ≥90 mmHg, oxygen saturation ≥90% on room air, ability to maintain oral intake, and normal mental status 1, 3

Transition to Oral Therapy

Switch from IV to oral antibiotics when the patient is hemodynamically stable, clinically improving, able to take oral medications, and has normal GI function—typically by day 2-3 of hospitalization. 1, 4, 3

Oral step-down options:

• Amoxicillin 1 g orally three times daily PLUS azithromycin 500 mg orally daily 1
• Amoxicillin-clavulanate 875/125 mg orally twice daily PLUS azithromycin 500 mg orally daily 1
• Doxycycline 100 mg orally twice daily (continuation from IV doxycycline) 1
• Respiratory fluoroquinolone (levofloxacin 750 mg orally daily or moxifloxacin 400 mg orally daily) 1

Critical Timing Considerations

Administer the first antibiotic dose immediately upon diagnosis, ideally while still in the emergency department. Delayed administration beyond 8 hours increases 30-day mortality by 20-30% in hospitalized patients 1, 6

Diagnostic Testing

Obtain blood cultures and sputum Gram stain/culture before initiating antibiotics in ALL hospitalized patients to allow pathogen-directed therapy and de-escalation 1, 4

• Test all patients for COVID-19 and influenza when these viruses are common in the community 6, 5
• Consider urinary antigen testing for Legionella pneumophila serogroup 1 in severe CAP or ICU patients 1

Supportive Care

Oxygen therapy: Target PaO₂ >8 kPa (60 mmHg) and SaO₂ >92% 4, 3

• For COPD patients with ventilatory failure, guide oxygen by repeated arterial blood gases to avoid CO₂ retention 4, 3

Monitoring parameters (assess at least twice daily): Temperature, respiratory rate, pulse, blood pressure, mental status, oxygen saturation, and inspired oxygen concentration 4, 3

Systemic corticosteroids: Administration within 24 hours of severe CAP development may reduce 28-day mortality 6

Management of Treatment Failure

If no clinical improvement by day 2-3, obtain repeat chest radiograph, CRP, white cell count, and additional microbiological specimens 2, 4, 3

• Consider chest CT to evaluate for complications (pleural effusions, lung abscess, central airway obstruction) 4, 3
• For non-severe pneumonia initially on amoxicillin monotherapy: Add or substitute a macrolide 4, 3
• For non-severe pneumonia on combination therapy: Switch to respiratory fluoroquinolone 4, 3
• For severe pneumonia not responding to combination therapy: Consider adding rifampicin 4, 3

Follow-Up and Discharge Planning

Discharge criteria: Clinical stability achieved on oral therapy, no unstable coexisting illnesses, and safe home environment 3

• Chest radiograph is not required before hospital discharge if patient is clinically improving 4, 3
• Schedule clinical review at 6 weeks for all hospitalized patients 4, 3
• Obtain chest radiograph at 6 weeks only for patients with persistent symptoms, physical signs, or high risk for underlying malignancy (smokers, age >50 years) 4, 3

Prevention Strategies

Vaccination (assess at hospital admission) 4, 3:

• Pneumococcal: All adults ≥65 years or those 19-64 with underlying conditions should receive 20-valent pneumococcal conjugate vaccine alone OR 15-valent pneumococcal conjugate vaccine followed by 23-valent pneumococcal polysaccharide vaccine one year later 2, 5
• Influenza: Annual vaccination for all patients, especially during fall and winter 2, 4, 5
• COVID-19: Vaccination for all adults 5

Smoking cessation: Make this a goal for all patients hospitalized with CAP who smoke 2, 4

Critical Pitfalls to Avoid

• Never use macrolide monotherapy in hospitalized patients—it provides inadequate coverage for typical bacterial pathogens like S. pneumoniae 1
• Never use macrolide monotherapy in areas where pneumococcal macrolide resistance exceeds 25%—this leads to treatment failure 1, 5
• Avoid indiscriminate fluoroquinolone use in uncomplicated outpatient CAP due to resistance concerns and serious adverse events 1, 3
• Do not automatically escalate to broad-spectrum antibiotics based solely on age or comorbidities without documented risk factors for resistant organisms 1
• Avoid extending therapy beyond 7-8 days in responding patients without specific indications—longer courses increase antimicrobial resistance risk without improving outcomes 1
• Do not use oral cephalosporins (cefuroxime, cefpodoxime) as step-down therapy—these have inferior in vitro activity compared to high-dose amoxicillin 1

Special Populations

Elderly patients (≥65 years): Lower threshold for hospitalization, consider combination therapy even in outpatient setting, adjust doses for renal function 2, 7, 8

COPD/asthma patients: Require combination therapy even in outpatient setting due to increased risk of P. aeruginosa and resistant pathogens 2

Nursing home residents: Use respiratory fluoroquinolone alone or amoxicillin-clavulanate plus macrolide 1

Suspected aspiration with infection: Use amoxicillin-clavulanate or clindamycin 1