What are the current guidelines for treating community-acquired pneumonia (CAP)?

Current Guidelines for Community-Acquired Pneumonia

Treatment Selection Based on Patient Setting

The most recent IDSA/ATS consensus guidelines (2007) recommend that empiric antibiotic therapy for CAP should be stratified by treatment setting and risk factors, with hospitalized non-ICU patients receiving a β-lactam plus macrolide or respiratory fluoroquinolone monotherapy as first-line treatment. 1

Outpatient Treatment

For previously healthy outpatients without recent antibiotic use:

• First-line: Macrolide (azithromycin or clarithromycin) or doxycycline 1, 2
• Amoxicillin 1 g every 8 hours is recommended by ATS as an alternative first-line option 2
• Doxycycline 100 mg twice daily (with first dose of 200 mg to achieve adequate serum levels rapidly) 2

For outpatients with comorbidities (COPD, diabetes, renal/heart failure, malignancy) or recent antibiotic use:

• Preferred: Respiratory fluoroquinolone (levofloxacin or moxifloxacin) alone 1, 2
• Alternative: Advanced macrolide plus high-dose amoxicillin or amoxicillin-clavulanate 1
• Patients with recent antibiotic exposure within 90 days should receive a different antibiotic class due to resistance risk 2

Hospitalized Non-ICU Patients

Standard regimen:

• β-lactam (ceftriaxone 1-2 g every 24 hours, cefotaxime, or ampicillin-sulbactam) PLUS macrolide (azithromycin or clarithromycin) 1, 2
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin) 1, 2

Severe CAP/ICU Patients

For patients WITHOUT Pseudomonas risk factors:

• β-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS either azithromycin OR respiratory fluoroquinolone 1, 2

For patients WITH Pseudomonas risk factors (structural lung disease, recent hospitalization, recent broad-spectrum antibiotics):

• Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) PLUS ciprofloxacin OR levofloxacin 1
• Alternative: Antipseudomonal β-lactam PLUS aminoglycoside (gentamicin, tobramycin, or amikacin) PLUS azithromycin or respiratory fluoroquinolone 1

For suspected community-acquired MRSA:

• Add vancomycin or linezolid to the above regimens 1
• Risk factors include prior MRSA infection, recent hospitalization, or recent antibiotic use 2

Timing and Route of Administration

Critical timing considerations:

• For patients admitted through the emergency department, administer the first antibiotic dose while still in the ED 1
• Early antibiotic administration is associated with improved outcomes and reduced mortality 2

Switching from IV to oral therapy:

• Switch when patient is hemodynamically stable, improving clinically, able to ingest medications, and has functioning GI tract 1
• Specific criteria: afebrile (<100°F) on two occasions 8 hours apart, improvement in cough and dyspnea, decreasing white blood cell count 1
• Discharge can occur on the same day as oral switch if medical and social factors permit 1

Duration of Therapy

Minimum treatment duration:

• 5 days minimum for most patients 1, 3, 4
• Patient must be afebrile for 48-72 hours and have no more than 1 sign of clinical instability before discontinuing therapy 1, 3
• Clinical stability criteria include: temperature <37.8°C, heart rate ≤100 bpm, respiratory rate ≤24/min, systolic BP ≥90 mmHg, oxygen saturation ≥90%, ability to eat, and normal mentation 3

Extended duration:

• 7 days for suspected or proven MRSA or Pseudomonas aeruginosa 3
• 14-21 days for severe pneumonia or when Legionella, staphylococcal, or gram-negative enteric bacilli are confirmed 2
• Longer duration needed if initial therapy was not active against identified pathogen or complicated by extrapulmonary infection (meningitis, endocarditis) 1

Management of Treatment Failure

Evaluation approach for patients not responding within 72 hours:

• Reassess for drug-resistant or unusual pathogens, non-pneumonia diagnosis (inflammatory disease, pulmonary embolus), or pneumonia complications 1
• Obtain CT scan to reveal unsuspected pleural fluid collections, lung nodules, or cavitation 1
• Send lower respiratory tract secretions (sputum or endotracheal aspirate) for culture, including tuberculosis testing 1
• Consider Legionella urinary antigen testing (positive in >80% of L. pneumophila serogroup 1 infections) 1
• Serologic testing for Legionella, Mycoplasma pneumoniae, viral agents, and endemic fungi 1
• Consider open lung biopsy if extensive evaluation is non-diagnostic and patient is seriously ill 1

Bronchoscopy indications:

• Consider in patients <55 years old with multilobar disease who are nonsmokers 1
• Generally not needed for routine cases; patience is necessary for radiographic clearing 1

Prevention Strategies

Vaccination recommendations:

• Pneumococcal vaccine (23-valent polysaccharide) for all patients ≥65 years and at-risk populations 1
• Effectiveness: 56-81% overall, 65-84% in patients with diabetes, coronary artery disease, CHF, chronic pulmonary disease, and asplenia 1
• 75% effective in immunocompetent patients >65 years 1

Influenza vaccination:

• Annual influenza vaccine for all at-risk patients 1
• Influenza epidemics have resulted in 20,000-40,000 deaths per epidemic between 1972-1992 1

Smoking cessation:

• Promote smoking cessation in all patients as it eliminates an important risk factor for CAP 1, 3

Common Pitfalls to Avoid

Antibiotic selection errors:

• Do NOT rely on sputum Gram stain alone to guide initial therapy 1
• Avoid fluoroquinolone overuse; reserve for patients with β-lactam allergies or specific indications to prevent resistance 2
• Do NOT use cephalosporins alone without macrolide coverage, as this misses atypical pathogens 2

Risk stratification errors:

• Abandon the healthcare-associated pneumonia (HCAP) classification; only cover empirically for MRSA or Pseudomonas if locally validated risk factors are present 3
• Risk factors for multidrug-resistant pathogens include: hospitalization >2 days in previous 90 days, antibiotic use in previous 90 days, nonambulatory status, tube feeds, immunocompromised status, acid-suppressive therapy, chronic hemodialysis in preceding 30 days 5, 6

Timing errors:

• Do NOT delay initial antibiotic therapy beyond 72 hours without reassessment 1
• Do NOT continue IV therapy once oral switch criteria are met 1

Duration errors:

• Do NOT treat for less than 5 days even if clinical stability is achieved earlier 1, 3
• Do NOT routinely extend therapy beyond 8 days in responding patients without specific indications 2