Community acquired pneumonia: aetiology and prognostic index evaluation

A 10 month prospective study of all adults admitted to Waikato Hospital with community acquired pneumonia was performed to assess aetiology, mortality, hospital stay, and the value of a prognostic index based on that obtained from a British Thoracic Society study. The 92 patients in the survey had a mean age of 56 (range 13-97) years. A microbiological diagnosis was established in 72%; Streptococcus pneumoniae (33%), Mycoplasma pneumoniae (18%), and influenza A virus (8%) were the most common microorganisms. Other causative organisms were Legionella pneumophila (4 cases), Staphylococcus aureus (3), Klebsiella pneumoniae (2), Haemophilus influenzae (2), Nocardia brasiliensis (1), and Acinetobacter calcoaceticus (1). Chlamydia sp, influenza B virus and adenovirus were each found in one case; all were cultured on nasopharygeal aspirates. Aspiration was considered to be the underlying cause in five patients, two with epilepsy and one with pseudobulbar palsy. Five of the six deaths that occurred were in patients over 75 years of age and the other was 69. In four of the six the established causative organisms were Chlamydia sp (1), K pneumoniae (1), and S aureus (2). Patients had a 16 fold increased risk of death if they had two or more of the following on admission: a respiratory rate of 30/minute or more, diastolic blood pressure of 60 mm Hg or less, and either confusion or a plasma urea concentration greater than 7.0 mmol/l.