Treatment of Community-Acquired Pneumonia
For adults with community-acquired pneumonia, treatment should be initiated immediately with empiric antibiotics based on severity and setting: outpatients without comorbidities receive amoxicillin or doxycycline; outpatients with comorbidities receive a respiratory fluoroquinolone or β-lactam plus macrolide; non-severe hospitalized patients receive β-lactam plus macrolide combination therapy (such as ceftriaxone plus azithromycin); and severe/ICU patients receive intravenous β-lactam plus macrolide combination therapy, with treatment duration of 5-7 days for most patients who achieve clinical stability. 1, 2, 3
Initial Assessment and Severity Stratification
Severity assessment determines treatment location and antibiotic selection. Use clinical criteria including vital signs, oxygenation, mental status, and comorbidities to stratify patients into outpatient, non-severe inpatient, or severe/ICU categories. 1, 2
Obtain chest radiograph to confirm diagnosis in all patients with suspected CAP, as radiographic confirmation is required before initiating empiric therapy. 1, 3
Do NOT withhold antibiotics based on procalcitonin levels. Empiric antibiotic therapy should be initiated regardless of initial serum procalcitonin level, as procalcitonin cannot reliably distinguish bacterial from viral pneumonia and sensitivity ranges from only 38% to 91%. 1
Test for COVID-19 and influenza when these viruses are circulating in the community, as positive results may affect treatment decisions and infection prevention strategies. 3
Outpatient Treatment
Previously Healthy Patients Without Recent Antibiotic Use
First-line therapy is amoxicillin 1 g every 8 hours for patients without comorbidities or recent antibiotic exposure. 2, 4
Alternative first-line option is doxycycline 100 mg twice daily (with first dose of 200 mg to achieve adequate serum levels more rapidly). 2, 4
Macrolides (azithromycin or clarithromycin) are acceptable alternatives for patients without comorbidities, though resistance concerns exist in some regions. 1, 2
Patients With Comorbidities or Recent Antibiotic Use
Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) is recommended for patients with chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; asplenia; immunosuppression; or antibiotic use within the previous 3 months. 1, 2, 4
Alternative is combination therapy with β-lactam plus macrolide (such as amoxicillin-clavulanate plus azithromycin) for patients with comorbidities. 1, 2
Patients with recent exposure to one antibiotic class should receive treatment from a different class due to increased risk for bacterial resistance. 4
Special Consideration: Aspiration Pneumonia
- For suspected aspiration with infection, use amoxicillin-clavulanate or clindamycin to provide anaerobic coverage. 2
Non-Severe Hospitalized Patients
Standard regimen is β-lactam plus macrolide combination therapy: ampicillin-sulbactam 1.5-3 g every 6 hours, cefotaxime 1-2 g every 8 hours, ceftriaxone 1-2 g daily, or ceftaroline 600 mg every 12 hours PLUS azithromycin 500 mg daily or clarithromycin 500 mg twice daily. 1, 2, 3
Alternative is respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) for patients intolerant of β-lactams or macrolides. 1, 2, 4
Oral antibiotics are preferred when there are no contraindications to oral therapy, as outcomes are equivalent to parenteral therapy in non-severe pneumonia. 1, 2
β-lactam plus macrolide combination therapy is associated with 26% to 68% relative reductions in short-term mortality compared with β-lactam monotherapy in observational studies, though one randomized trial showed noninferiority of β-lactam monotherapy. 5
Severe CAP/ICU Patients
Immediate parenteral antibiotic administration is mandatory for patients with severe pneumonia, as delays are associated with increased mortality. 1, 2, 4
Standard regimen is intravenous β-lactam plus macrolide: ceftriaxone 1-2 g daily or cefotaxime 1-2 g every 8 hours PLUS azithromycin 500 mg daily or clarithromycin 500 mg twice daily. 1, 2
Alternative is β-lactam plus respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) for patients intolerant of macrolides. 1, 2
Risk Factors for Drug-Resistant Pathogens
Add MRSA coverage (vancomycin 15 mg/kg every 12 hours or linezolid 600 mg every 12 hours) for patients with prior MRSA infection, recent hospitalization with parenteral antibiotics within 90 days, or positive nasal PCR. Obtain cultures and nasal PCR to allow de-escalation. 1, 2
Add Pseudomonas coverage with antipseudomonal β-lactam (piperacillin-tazobactam 4.5 g every 6 hours, cefepime 2 g every 8 hours, or meropenem 1 g every 8 hours) for patients with structural lung disease, recent hospitalization with parenteral antibiotics, or prior Pseudomonas isolation. 1, 2
Route of Administration and Transition to Oral Therapy
Switch from intravenous to oral antibiotics when patients are hemodynamically stable, afebrile for 24 hours, showing clinical improvement in cough and dyspnea, have decreasing white blood cell count, and can tolerate oral intake. 1, 2, 4
Using objective clinical criteria for IV-to-oral transition reduces hospital length of stay by 1.9 days without increasing treatment failure. 5
Review route of administration daily, with ward pharmacists highlighting prescription charts where parenteral therapy continues unnecessarily. 1
Duration of Antibiotic Therapy
Minimum duration is 5 days for most patients who are afebrile for 48-72 hours and have no more than one sign of clinical instability. 1, 2, 4
Standard duration is 7 days for uncomplicated pneumonia managed in the community or hospital. 1, 2
Extend treatment to 10 days for severe microbiologically undefined pneumonia. 1
Extend treatment to 14-21 days when Legionella, staphylococcal, or Gram-negative enteric bacilli pneumonia are suspected or confirmed. 1, 2, 4
Management of Treatment Failure
Conduct careful clinical review by an experienced clinician of the history, examination, prescription chart, and all investigation results for patients who fail to improve within 48-72 hours. 1, 2, 4
Obtain repeat chest radiograph, CRP, white cell count, and additional microbiological specimens including blood cultures and respiratory samples. 1, 2, 4
For non-severe pneumonia on amoxicillin monotherapy, add or substitute a macrolide to cover atypical pathogens. 1
For non-severe pneumonia on combination therapy, consider switching to a respiratory fluoroquinolone with effective pneumococcal coverage. 1
For severe pneumonia not responding to combination therapy, consider adding rifampicin. 1
Common Pitfalls and Caveats
Avoid delaying antibiotic administration, as the first dose should be given in the emergency department for hospitalized patients, with delays associated with increased mortality particularly in severe pneumonia. 2, 4
Do not overuse fluoroquinolones in outpatients without comorbidities, as this promotes resistance; reserve them for patients with β-lactam allergies or specific indications despite their convenience and broad coverage. 1, 4, 6
Ensure adequate coverage for atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila), as β-lactam monotherapy misses these organisms and is associated with higher mortality. 4, 6, 5
Be aware of fluoroquinolone warnings: The FDA has issued alerts about serious adverse events including tendon rupture, peripheral neuropathy, CNS effects, and QT prolongation, particularly in elderly patients and those with risk factors. 7, 8
Monitor for Clostridium difficile-associated diarrhea, which can occur with all antibacterial agents including azithromycin and fluoroquinolones, and may present up to 2 months after antibiotic administration. 7
Adjust therapy based on culture results when available to narrow spectrum and reduce unnecessary broad-spectrum antibiotic exposure. 1, 2, 4