Microbial aetiology of community-acquired pneumonia in hospitalised patients

Adult patients hospitalised with community-acquired pneumonia were studied prospectively to determine the microbial aetiology of pneumonia. Between Ap ril 1996 and March 1997, blood and sputum samples were collected for cultur e. Throat swabs were obtained for isolation of viruses and for detection of antigens of Chlamydia pneumoniae, influenza viruses A and B, respiratory s yncytial virus and parainfluenza virus. Antibodies against Legionella spp., Mycoplasma pneumoniae, Chlamydia pneumoniae, Chlamydia psittaci, Coxiella burnetii, influenza viruses A and B, respiratory syncytial virus, adenoviru s and parainfluenza virus were tested in serum samples. Two hundred eleven patients were included in the study: paired sera were available from 152 pa tients. Blood culture was positive in 23 (10.9%) patients, Streptococcus pn eumoniae being the bacterium isolated most frequently. A fourfold or greate r rise or fall in the Chlamydia pneumoniae IgG and/or IgM antibody titre wa s found in 20 (9.5%) patients and a high antibody titre (greater than or eq ual to 1:512) in the first and/or the second serum sample in 18 (18.5%) pat ients. Antibodies confirming acute Mycoplasma pneumoniae infection were fou nd in 12 (5.7%) patients, Legionella spp. in six (2.8%), Chlamydia psittaci in two and Coxiella burnetii in one. Three patients had pulmonary tubercul osis. Only two patients had a virus present in the throat swab (adenovirus in one patient and echovirus in the other), and in nine patients, viral ant igen was detected. Acute viral infection was confirmed in 51 (24.1%) patien ts. Bacterial pneumonia was diagnosed in 84 (39.8%) patients, 23 of whom ha d concurrent viral infection. Acute viral pneumonia without any other ident ified pathogen was diagnosed in 28 patients. Streptococcus pneumoniae and C hlamydia pneumoniae were the most frequently identified microorganisms.