What is the treatment for a patient with pneumonia, considering factors such as severity of symptoms, age, and underlying health conditions?

Treatment of Pneumonia

For outpatient pneumonia in healthy adults, amoxicillin 1 g orally three times daily for 5-7 days is the preferred first-line therapy, while hospitalized patients without ICU-level severity should receive ceftriaxone 1-2 g IV daily plus azithromycin 500 mg daily, with the first antibiotic dose administered within 4 hours of hospital arrival. 1, 2

Outpatient Treatment

Healthy Adults Without Comorbidities

• Amoxicillin 1 g orally three times daily for 5-7 days is the preferred first-line agent, providing excellent coverage against Streptococcus pneumoniae and other common respiratory pathogens 1, 3
• Doxycycline 100 mg orally twice daily serves as an acceptable alternative for patients who cannot tolerate amoxicillin 1
• Macrolides (azithromycin 500 mg day 1, then 250 mg daily for 4 days, or clarithromycin 500 mg twice daily) should only be used when local pneumococcal macrolide resistance is documented to be <25% 1, 4

Adults With Comorbidities

• Comorbidities include COPD, diabetes, chronic heart/liver/renal disease, malignancy, or recent antibiotic use within 3 months 1
• Combination therapy with β-lactam plus macrolide is recommended: amoxicillin-clavulanate 875 mg/125 mg orally twice daily plus azithromycin 500 mg day 1, then 250 mg daily 1
• Alternative monotherapy with respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) is equally effective but should be reserved for specific situations due to resistance concerns 1

Hospitalized Non-ICU Patients

Standard Regimen

• Ceftriaxone 1-2 g IV daily plus azithromycin 500 mg daily is the preferred regimen, providing coverage for both typical bacterial pathogens (S. pneumoniae, H. influenzae) and atypical organisms (Mycoplasma, Legionella, Chlamydophila) 1, 5
• Alternative β-lactams include cefotaxime 1-2 g IV every 8 hours or ampicillin-sulbactam 3 g IV every 6 hours, always combined with azithromycin 1
• Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily) is equally effective as combination therapy 1, 6

Penicillin-Allergic Patients

• Respiratory fluoroquinolone is the preferred alternative for patients with documented penicillin allergy 1
• Aztreonam 2 g IV every 8 hours plus azithromycin 500 mg IV daily can be used for patients with contraindications to fluoroquinolones 1

Critical Timing

• The first antibiotic dose must be administered within 4 hours of hospital arrival, as delayed administration beyond 8 hours increases 30-day mortality by 20-30% 2, 1

Severe CAP Requiring ICU Admission

Mandatory Combination Therapy

• All ICU patients require combination therapy with β-lactam plus either azithromycin or respiratory fluoroquinolone—monotherapy is inadequate for severe disease 1, 3
• Preferred regimen: ceftriaxone 2 g IV daily plus azithromycin 500 mg IV daily 1, 3
• Alternative: ceftriaxone 2 g IV daily plus levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily 1

Risk Factors for Resistant Pathogens

• Add antipseudomonal coverage for patients with structural lung disease, recent hospitalization with IV antibiotics within 90 days, or prior respiratory isolation of P. aeruginosa 1
  • Regimen: antipseudomonal β-lactam (piperacillin-tazobactam 4.5 g IV every 6 hours, cefepime 2 g IV every 8 hours, or meropenem 1 g IV every 8 hours) plus ciprofloxacin 400 mg IV every 8 hours or levofloxacin 750 mg IV daily, plus aminoglycoside 1
• Add MRSA coverage for patients with prior MRSA infection/colonization, recent hospitalization with IV antibiotics, post-influenza pneumonia, or cavitary infiltrates 1
  • Add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) or linezolid 600 mg IV every 12 hours 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, 2
• Typical duration for uncomplicated CAP is 5-7 days 1, 3
• Extended duration of 14-21 days is required for Legionella pneumophila, Staphylococcus aureus, or Gram-negative enteric bacilli 1, 2

Transition from IV to Oral Therapy

• Switch from IV to oral antibiotics when the patient is hemodynamically stable, clinically improving, afebrile for 24 hours, able to take oral medications, and has normal GI function—typically by day 2-3 of hospitalization 2, 1
• Oral step-down options include amoxicillin 1 g three times daily plus azithromycin 500 mg daily 1
• Patients can be discharged on the same day as the switch to oral therapy if other medical and social factors permit 2

Diagnostic Testing for Hospitalized Patients

• Obtain blood cultures and sputum Gram stain/culture before initiating antibiotics in all hospitalized patients to allow pathogen-directed therapy and track resistance patterns 1, 7
• Test all patients for COVID-19 and influenza when these viruses are common in the community, as their diagnosis may affect treatment and infection prevention strategies 5

Management of Treatment Failure

• If no clinical improvement by day 2-3, obtain repeat chest radiograph, CRP, white cell count, and additional microbiological specimens 8, 2
• Consider chest CT scan to identify empyema, lung abscess, pulmonary embolism, or alternative diagnoses 8
• For non-severe pneumonia initially treated with amoxicillin monotherapy, add or substitute a macrolide 3, 8
• For severe pneumonia not responding to combination therapy, consider adding rifampicin 3
• Switch to respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) if the current regimen has failed and no complications are found 8

Critical Pitfalls to Avoid

• Never use macrolide monotherapy in areas where pneumococcal macrolide resistance exceeds 25%, as this leads to treatment failure 1
• Never use macrolide monotherapy for hospitalized patients, as it provides inadequate coverage for typical bacterial pathogens like S. pneumoniae 1
• Avoid indiscriminate fluoroquinolone use in uncomplicated outpatient CAP due to FDA warnings about serious adverse events and resistance concerns 1
• Do not change antibiotic therapy within the first 72 hours unless there is marked clinical deterioration or bacteriologic data necessitate a change 2
• Never extend the same antibiotics without reassessing the diagnosis in patients with inadequate response—consider resistant organisms or complications 8

Follow-Up

• Schedule clinical review at 6 weeks for all hospitalized patients, with chest radiograph reserved for those with persistent symptoms, physical signs, or high risk for underlying malignancy (smokers, age >50 years) 1, 3
• Chest radiograph need not be repeated prior to hospital discharge in patients with satisfactory clinical recovery 3

Prevention

• Administer pneumococcal vaccine to all patients ≥65 years and those with high-risk conditions (chronic lung/heart/renal/liver disease, diabetes, immunosuppression) 1, 3
• Offer annual influenza vaccine to all patients, especially during fall and winter 1, 3
• Make smoking cessation a goal for all patients hospitalized with CAP who smoke, as smoking is the strongest risk factor for invasive pneumococcal disease in immunocompetent adults 2, 3