What is the treatment for bacterial infections referred to as Cap treatment?

Treatment of Community-Acquired Pneumonia (CAP)

For outpatients without comorbidities, start with amoxicillin at high doses (preferred) or a macrolide (azithromycin or clarithromycin); for hospitalized patients, use a β-lactam (amoxicillin or ceftriaxone) plus a macrolide (azithromycin or clarithromycin). 1

Outpatient Treatment Algorithm

Previously Healthy Patients (No Risk Factors)

• First-line: Amoxicillin at higher doses is preferred 2, 1
• Alternative: Macrolide monotherapy (azithromycin or clarithromycin) 1
• For penicillin allergy: Erythromycin or doxycycline 2

The British Thoracic Society guidelines prioritize amoxicillin because it minimizes interference with established prescribing patterns and avoids widespread fluoroquinolone use that drives resistance 2. This differs from North American guidelines that favor macrolides as first-line therapy 2.

Patients with Comorbidities or Recent Antibiotic Use

• Recommended: Respiratory fluoroquinolone (levofloxacin 750 mg) OR β-lactam plus macrolide 2, 1
• For COPD without recent antibiotics/steroids: Amoxicillin-clavulanate or second-generation cephalosporin 2
• For COPD with recent antibiotics/steroids: Respiratory fluoroquinolone plus macrolide 2

Hospitalized Patient Treatment

Non-ICU Patients

• Standard regimen: β-lactam (amoxicillin or ceftriaxone) PLUS macrolide (erythromycin or clarithromycin) 1
• This combination covers both typical pathogens (S. pneumoniae, H. influenzae) and atypical organisms (Mycoplasma, Chlamydia) 2

ICU or Critically Ill Patients

• Empiric therapy: β-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS either:
  • Azithromycin, OR
  • Respiratory fluoroquinolone (levofloxacin 750 mg) 2
• Add anti-MRSA coverage (vancomycin or linezolid) in selected high-risk patients 2
• For Pseudomonas risk: Use antipseudomonal β-lactam plus aminoglycoside plus either azithromycin or fluoroquinolone 2

Duration of Therapy

Treat for minimum 5 days AND ensure patient is afebrile for 48-72 hours with no more than 1 sign of clinical instability before stopping antibiotics. 2, 1

• Standard bacterial CAP: 5-7 days 2
• Mycoplasma or Chlamydia: 10-14 days 2
• Legionella or Staphylococcus aureus: 21 days 2
• Longer duration needed if initial therapy was inactive against identified pathogen or if complicated by extrapulmonary infection 2

Switching from IV to Oral Therapy

Switch to oral antibiotics when the patient is hemodynamically stable, clinically improving, able to ingest medications, and has normally functioning GI tract. 2, 1

• Discharge as soon as clinically stable with no other active medical problems 2
• Inpatient observation while receiving oral therapy is unnecessary 2

Pathogen-Directed Therapy

Once a pathogen is identified through reliable microbiological methods, narrow antimicrobial therapy to target that specific organism. 2, 1

This de-escalation strategy reduces unnecessary broad-spectrum antibiotic exposure and helps preserve antibiotic effectiveness 2.

Special Populations and Situations

Community-Acquired MRSA

• Add vancomycin or linezolid to the regimen 2
• Consider in patients with necrotizing pneumonia, cavitation, or severe illness 2

Pandemic Influenza (H5N1 suspected)

• Oseltamivir PLUS antibacterial agents targeting S. pneumoniae and S. aureus 2
• Use droplet precautions until H5N1 ruled out 2

Timing of First Dose

• For ED admissions, administer first antibiotic dose while still in the emergency department 2
• Early treatment (within 48 hours of symptom onset) improves outcomes 2

Common Pitfalls to Avoid

Do not use serum biomarkers alone to decide antibiotic initiation in non-critically ill patients. 2 While elevated WBC, CRP >100 mg/L, or procalcitonin >0.5 ng/mL suggest bacterial infection, clinical judgment must guide therapy 2.

Do not routinely prescribe antibiotics for COVID-19 patients receiving immunomodulators (corticosteroids, IL-6 inhibitors) as evidence for increased bacterial infection risk is weak 2.

Approximately 15% of CAP patients fail initial therapy—use a systematic approach to determine the cause rather than empirically broadening coverage 2.