Chlamydial pneumonia in children requiring hospitalization: effect of mixed infection on clinical outcome.

The etiology of community-acquired pneumonia (CAP) in a children's hospital was studied among 209 previously healthy children treated from August 1, 2001 to July 31, 2002. A total of 26 children (12.4%) with a diagnosis of chlamydial infection were included in this study. The diagnosis of chlamydial infection was based on either a positive immunofluorescent assay result for chlamydial antigen in sputum, or positive serologic results for immunoglobulin M (IgM), an IgG titer >/=1:640 or a 4-fold rise in IgG titer by microimmunofluorescence test. Fourteen patients (53.8%) were female and 20 (76.9%) were less than 5 years of age. The onset of infection occurred between August and January in 21 cases (80.7%). Twenty one patients (80.8%) had other pathogens identified. Fever and cough were the most common presenting symptoms. The signs and symptoms were similar for the children with and without coinfection except for tachypnea and wheezing sound, which were significantly more common in patients with mixed infection. None of the laboratory parameters seemed to be specific for chlamydial infection; however, serum C-reactive protein level was significantly higher in cases with mixed infection. Among the 26 children, 12 (46.2%) needed respiratory therapy, and most of them (91.7%, 11/12) had coinfection. Two patients (7.7%) with mixed infection were admitted to the pediatric intensive care unit. One had lobar pneumonia with pleural effusion and the other had necrotizing pneumonia requiring surgical intervention. None of the patients died. In conclusion, Chlamydia sp. was identified in 12.4% of children with CAP in this series, and mixed infections were common (80.8%) among these patients. The clinical course of chlamydial pneumonia was not serious in most patients, but alertness is needed to the possibility of developing severe pneumonia in cases with bacterial coinfection.