Chlamydia pneumoniae is an important cause of community-acquired pneumoniain school-aged children: Serological results of a prospective, population-based study

The aetiology of community-acquired pneumonia in childhood was studied in t he total population of 8851 children in the area of 4 municipalities in eas tern Finland, All cases of community-acquired pneumonia (n = 201) were regi stered during a surveillance period of 12 months between September 1, 1981 and August 31, 1982, The diagnosis of pneumonia was verified radiologically in all identified cases. The diagnosis of chlamydial infection was based o n an antibody response measured by complement fixation (CF), by enzyme immu noassay (EIA; IgG or IgM) or by microimmunofluorescence (MIF; IgG or IgM), and the diagnosis of mycoplasmal infection on CF alone. In total, 29 cases of Chlamydia sp, infection were diagnosed; 20 were caused by Chlamydia pneu moniae, Thus, C. pneumoniae was an aetiological agent in 10% of the 201 pne umonia eases: the proportion was 9% for children aged 5-9 y and 31% for tho se aged 10 y or more. In the study population, the total incidence of C. pn eumoniae pneumonia was 2.3/1000/y. Mycoplasma pneumoniae serology (CF) was positive in 44 patients (22%); the total incidence of M. pneumoniae pneumon ia was 5.0/1000/y. Serological evidence of both Chlamydiae and M. pneumonia e was detected in 9 (4%) patients, Our results indicate that C, pneumoniae is an important cause of community-acquired pneumonia in school-aged childr en, Diagnostic serological response to Chlamydia species or;M. pneumoniae w as found in 42% of pneumonia patients between 5 and 9 y of age and in 67% o f patients aged 10 y or more. Thus, we suggest that macrolides should be co nsidered as an empirical antimicrobial treatment for community-acquired pne umonia, especially in school-aged outpatients.