What is the recommended antibiotic treatment for Community-Acquired Pneumonia (CAP) in a patient with a history of Coronary Artery Bypass Graft (CABG)?

Antibiotic Treatment for Community-Acquired Pneumonia in Patients with CABG History

Treat patients with a history of CABG who develop community-acquired pneumonia with the same antibiotic regimens recommended for patients with comorbidities, as CABG history represents a significant cardiovascular comorbidity requiring combination therapy rather than monotherapy. 1

Outpatient Treatment (If Mild CAP)

For patients with CABG history who can be managed as outpatients, combination therapy with a β-lactam plus either a macrolide or doxycycline is recommended rather than monotherapy. 1

Preferred regimens include:

• Amoxicillin-clavulanate 875/125 mg twice daily PLUS azithromycin 500 mg on day 1, then 250 mg daily for 4 days 1
• Cefpodoxime or cefuroxime PLUS azithromycin or clarithromycin 500 mg twice daily 1
• Alternatively, respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) is acceptable 1

Avoid macrolide monotherapy in areas where pneumococcal macrolide resistance exceeds 25%, as this increases treatment failure risk. 1

Inpatient Non-ICU Treatment (Most Common Scenario)

For hospitalized patients with CABG history not requiring ICU admission, use either β-lactam plus macrolide combination therapy or respiratory fluoroquinolone monotherapy (both carry strong recommendations with high-quality evidence). 1

Preferred combination regimen:

• Ceftriaxone 1-2 g IV daily PLUS azithromycin 500 mg IV or oral daily 1, 2
• This provides coverage for typical bacterial pathogens (S. pneumoniae, H. influenzae) and atypical organisms (Mycoplasma, Chlamydophila, Legionella) 1

Alternative monotherapy regimen:

• Levofloxacin 750 mg IV or oral daily 1, 3
• This high-dose, short-course regimen maximizes concentration-dependent bactericidal activity and reduces resistance potential 4
• Oral and IV formulations are bioequivalent, allowing seamless transition 4

Administer the first antibiotic dose in the emergency department to reduce mortality risk. 1

ICU-Level Treatment (Severe CAP)

For patients requiring ICU admission, mandatory combination therapy with β-lactam PLUS either azithromycin OR respiratory fluoroquinolone is required. 1

Recommended regimen:

• Ceftriaxone 2 g IV daily OR cefotaxime 1-2 g IV every 8 hours PLUS azithromycin 500 mg IV daily 1
• OR ceftriaxone/cefotaxime PLUS levofloxacin 750 mg IV daily 1

For penicillin-allergic patients in the ICU:

• Respiratory fluoroquinolone PLUS aztreonam 2 g IV every 8 hours 1

Special Considerations for CABG Patients

Risk factors requiring broader spectrum coverage that may be present in post-CABG patients include:

For Pseudomonas aeruginosa risk (structural lung disease, recent hospitalization with IV antibiotics, prior P. aeruginosa isolation):

• 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 5, 1
• OR antipseudomonal β-lactam PLUS aminoglycoside (gentamicin 5-7 mg/kg IV daily) PLUS azithromycin 5

For MRSA risk (prior MRSA infection, recent hospitalization with IV antibiotics, cavitary infiltrates):

• Add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) OR linezolid 600 mg IV every 12 hours 5, 1

Transition to Oral Therapy and Duration

Switch from IV to oral therapy when the patient is:

• Hemodynamically stable 5
• Clinically improving 5
• Able to ingest medications 5
• Has normally functioning gastrointestinal tract 5

Treat for a minimum of 5 days and ensure the patient is afebrile for 48-72 hours with no more than one sign of clinical instability before discontinuation. 5, 1

Standard duration is 5-7 days for uncomplicated CAP, with longer courses (14-21 days) reserved for specific pathogens like Legionella, S. aureus, or gram-negative enteric bacilli. 1

Critical Pitfalls to Avoid

• Do not use monotherapy (amoxicillin alone or macrolide alone) in patients with CABG history, as cardiovascular comorbidity mandates combination therapy or fluoroquinolone monotherapy 1
• Do not delay antibiotic administration in hospitalized patients, as this increases mortality 1
• Do not automatically escalate to broad-spectrum antibiotics without documented risk factors for resistant organisms 1
• Obtain blood and sputum cultures before initiating antibiotics in all hospitalized patients to allow targeted de-escalation 1
• Do not extend therapy beyond 7 days in responding patients without specific indications, as this increases resistance risk 1