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Etiology and diagnosis of pneumonia requiring ICU admission
1Department of Anesthetics, University of Cape Town, South Africa.
Abstract:
The spectrum of pathogens and the microbiologic investigations used to obtain a diagnosis in 178 patients with severe pneumonia (88 percent requiring intermittent positive-pressure ventilation) are reviewed. Ninety-five patients had primary pneumonia, 31 had nosocomial pneumonia, 24 were immunocompromised patients, and 28 had aspiration pneumonia. While the spectrum of isolates conformed to the usual patterns for the different types of pneumonia, the incidence of Gram-positive infections (15 percent), predominantly Klebsiella pneumoniae, Staphylococcus aureus, (8 percent), and Legionella pneumophila (5 percent) in primary pneumonia was much higher than in community or general hospital-based studies, and only one case of Mycoplasma pneumoniae was identified. Gram stain of sputum or tracheal aspirate taken on intubation in primary pneumonia was reliably predictive of the causative organisms in both Gram-positive and Gram-negative infections when compared with infections proven by blood culture. Serologic studies were valuable in patients in whom no positive microbiologic diagnosis was evident; however, fiberoptic bronchoscopy contributed minimally to the microbiologic diagnosis in this group of patients. The cause of severe primary pneumonia differs from less severe disease, and this should be recognized when selecting empiric antibiotic therapy.
Insights
Severe pneumonia cases show higher Gram-positive infections, including Klebsiella pneumoniae and Staphylococcus aureus, than previously reported. Gram stain on intubation reliably predicts pathogens, guiding antibiotic therapy for severe primary pneumonia.
Area of Science:
- Infectious Diseases
- Pulmonology
- Microbiology
Background:
- Severe pneumonia presents unique challenges in diagnosis and treatment.
- Understanding the causative pathogens is crucial for effective management.
- Previous studies may not fully represent the spectrum of pathogens in severe pneumonia cases.
Purpose of the Study:
- To review the spectrum of pathogens causing severe pneumonia.
- To evaluate the utility of various microbiologic investigations in diagnosing severe pneumonia.
- To compare pathogen prevalence in different types of severe pneumonia.
Main Methods:
- Retrospective review of 178 patients with severe pneumonia.
- Analysis of pathogen identification through sputum Gram stain, blood cultures, and serologic studies.
- Evaluation of fiberoptic bronchoscopy's contribution to diagnosis.
Main Results:
- Gram-positive infections (15%), including Klebsiella pneumoniae and Staphylococcus aureus (8%), and Legionella pneumophila (5%) were more common in primary pneumonia than expected.
- Gram stain of respiratory secretions on intubation accurately predicted causative organisms.
- Serologic studies aided diagnosis when other methods failed; fiberoptic bronchoscopy had limited utility.
Conclusions:
- The etiology of severe primary pneumonia differs from less severe forms.
- Gram stain is a valuable tool for early pathogen identification in severe pneumonia.
- Empiric antibiotic selection should consider the distinct pathogen profile of severe primary pneumonia.