Outcome analysis of patients requiring mechanical ventilation with severe community-acquired pneumonia and identified bacterial pathogens

Background: Severe community-acquired pneumonia (CAP) is associated with high mortality. The choice of antibiotics should be guided by the distribution of bacterial pathogens. The purpose of this study was to analyze the causative bacteria and outcomes of patients with severe CAP in a medical intensive care unit (MICU) in Taiwan. The results may provide a basis of guidance for future empirical antibiotic treatments. Methods: We enrolled patients with severe CAP who were intubated and who required mechanical ventilation in an MICU in 2001. Only patients with identified bacterial pathogens were included. The bacterial distribution was determined, while differences in age, acute physiology and chronic health evaluation (APACHE) II scores, and initial PaO ₂/FiO₂ ratio between surviving and expired patients were compared. Results: Fifty-nine patients were enrolled and 75 isolates were obtained. Klebsiella pneumoniae was the most common bacteria (21.3%), followed by Pseudomonas aeruginosa and Acinetobacter baumannii. Staphylococcus aureus (8%) was the most-commonly isolated gram-positive organism, and half of its isolates were oxacillin-resistant (ORSA). The overall mortality was 55.9%. Multiple logistic regression analysis revealed that survivors had a significantly younger age and lower APACHE II scores. Conclusions: Gram-negative bacilli were the most-common causative pathogens among patients with severe CAP requiring mechanical ventilation. Antipseudomonal antibiotics or a carbapenem should be considered to cover Pseudomonas species, extended-spectrum β-lactamase-producing strains, and Acinetobacter species. If the isolated bacteria are gram-positive, care should be taken to cover the possibility of ORSA. Old age and higher APACHE II scores were associated with higher mortality.