Appropriateness of Antibiotic Combination Therapy for Severe Community-acquired Pneumonia in South Korea

• Inclusion Criteria:

• Adult patients aged 19 years or older who visited the emergency department and were hospitalized.
• Findings consistent with pneumonia diagnosis, meeting all of the following criteria:
• Radiologic evidence of pulmonary infiltration on chest X-ray or chest CT.
• At least two or more of the following clinical signs:

i) Body temperature ≥38°C or <36°C ii) White blood cell count ≥11,000/µL or <4,000/µL iii) Presence of purulent sputum or bronchial secretions

• Within 24 hours of admission, the patient meets one major criterion or three minor criteria according to ATS/IDSA classification:

• Major criteria:

i) Invasive mechanical ventilation ii) Use of vasopressors (vasopressor-dependent septic shock)

• Minor criteria:

i) Respiratory rate ≥30 breaths/min ii) PaO2/FiO2 ≤ 250 iii) Multilobar infiltrates iv) Confusion or disorientation v) BUN ≥20 mg/dL vi) WBC <4,000/mm³ vii) Platelet count <100,000/mm³ viii) Hypothermia (temperature <36°C) ix) Hypotension requiring aggressive fluid resuscitation

• Exclusion Criteria:

• Transferred from another hospital after >48 hours of hospitalization
• Died within 72 hours of hospital admission
• Transferred to another hospital within 14 days of admission
• Pneumonia occurring after >48 hours of mechanical ventilation, including home ventilators
• Detection of influenza or SARS-CoV-2 virus within 7 days of hospitalization
• Identified non-pneumonia infection requiring antibiotics within 72 hours of admission
• Detection of piperacillin/tazobactam-resistant Enterobacterales, Pseudomonas spp., or Acinetobacter spp. in respiratory or blood cultures within the past 90 days
• Antibiotic-related adverse events observed within 72 hours of assigned treatment, requiring discontinuation or change of antibiotics