Community-acquired pneumonia in Christchurch and Waikato 1999-2000: microbiology and epidemiology

To prospectively record current epidemiology and microbiology of community-acquired pneumonia in two New Zealand centres.

Between July 1999 and 2000 all adults admitted to Christchurch and Waikato Hospitals with community-acquired pneumonia were screened for study inclusion. All those enrolled had their medical history, clinical variables, inpatient management and clinical outcomes recorded and standardised microbial diagnostic testing carried out.

474 participants were enrolled with a mean age of 64 years and a microbial diagnosis was made in 197 cases (42%). Streptococcus pneumoniae (14%), Haemophilus influenzae (10%) and Influenza A virus (7%), Legionella spp (4%) and Mycoplasma pneumoniae (3%) were the most commonly isolated organisms. An 'atypical' organism was diagnosed in 8% of cases compared to 30% and 23% in previous Christchurch and Waikato studies respectively. Fourteen of the 67 S pneumoniae isolates (21%) had reduced susceptibility to penicillin, all with a MIC < or = 2 microg/mL, a level of reduced susceptibility not associated with worse patient outcomes. Clinical outcome included a mean hospital stay of 6.7 days and a 6 week mortality of 6%.

Although S pneumoniae was the most commonly isolated organism in this study there have been significant changes in the prevalence of atypical organisms since previous surveys. Ongoing surveillance of antibiotic resistance and variations in the prevalence of organisms causing community-acquired pneumonia is required to guide clinicians' empiric antibiotic use.