Aetiology of community-acquired pneumonia in hospitalized adult patients in New Caledonia

OBJECTIVE: To describe the aetiology of community-acquired pneumonia (CAP) in hospitalized adult patients in New Caledonia, a French archipelago in the South Pacific. METHODS: Confirmed CAP patients (n=137) were enrolled prospectively. Pathogens were detected by culture, molecular methods, serology on paired sera, immunofluorescence on nasopharyngeal swabs and antigen detection in urine. RESULTS: The aetiology of CAP was determined in 82 of 137 cases (59.8%), of which 31 exhibited two or more pathogens (37.8%). Hundred and seventeen pathogens were detected: Streptococcus pneumoniae was the most common one (41.0%), followed by influenza virus A (22.1%) and Haemophilus influenzae (10.2%). The frequency of atypical bacteria was low (6.0%). The most frequent and significant coinfection was S. pneumoniae with influenza A virus (P=0.004). Influenza virus was detected from nasopharyngeal swabs in four patients (15.4% of patients tested for influenza) and by PCR from pulmonary specimens in 15 patients (57.7%). CONCLUSIONS : Pneumoniae is the leading cause of CAP in New Caledonian adults. Viral-bacterial co-infections involving S. pneumoniae and influenza virus are very common during the winter. Such adult patients hospitalized with CAP are a clear sentinel group for surveillance of influenza. Vaccination against influenza and S. pneumoniae should be strengthened when risk factors are identified.