Legionella, Chlamydia pneumoniae and Mycoplasma infection in patients admitted to Christchurch Hospital with pneumonia

Abstract

Aims: To determine the incidence, clinical features and outcome of community acquired pneumonia caused by Mycoplasma pneumoniae, Legionella species, Coxiella burnetti, Chlamydia pneumoniae and Chlamydia psittaci requiring admission to hospital.

Methods: Over 12 months the clinical findings and severity of pneumonia were recorded prospectively. Sputum, blood, serum and urine samples were collected for diagnostic testing. Management was supervised by the admitting medical team. Subjects were followed-up six weeks after discharge.

Results: Two hundred and fifty-five patients met the entry criteria of whom 20 died, including five who had Legionella infection. M pneumoniae (16%) infection was more often of mild/moderate severity (95%), occurred in a younger age group (mean age 31.4 years, p=0.002), with more frequent myalgia and headache. The length of hospital stay was shorter and clearing of chest radiograph and return to normal activity occurred more rapidly in this group of patients. Legionellosis was common as judged by culture and serological testing (26 cases, 11%) and a further 22 cases were identified by polymerase chain reaction. Legionella infection was not distinguishable clinically from other pneumonias. C pneumoniae was uncommon (8 cases, 3%). C burnetti and C psittaci were not identified in this study.

Conclusions: Some cases of pneumonia caused by Mycoplasma pneumoniae can be identified at presentation, however pneumonia due to Legionella is not distinguishable on clinical grounds. Development of molecular diagnostic techniques may enable therapy to be directed against specific organisms earlier in the course of the disease.