A prospective diagnostic study clarifies the epidemiology of community-acquired lower respiratory infection in immunocompetent hospitalized children. The study was conducted from January 1999 through March 2000before pneumococcal conjugate vaccine was administered routinely.
Investigators used the results of blood or pleural fluid culture, polymerase chain reaction assay, viral direct fluorescent antibody testing, or serologic testing, to attempt to determine the causative agents of infection in 154 children, 2 months to 17 years of age (median age, 33 months), who were hospitalized with confirmed lower respiratory infection. A respiratory pathogen was identified in 79%.
Of the 60% of infections caused by bacteria, Streptococcus pneumoniae accounted for 73%; Mycoplasma pneumoniae, for 14%; and Chlamydia pneumoniae, for 9%. Viruses were identified in 45% of the childrenmost often, influenza virus A, respiratory syncytial virus, and parainfluenza types 1, 2, and 3. Nearly one quarter of patients had concurrent acute viral and bacterial disease. The percentage of identifiable infections attributable to viruses decreased with age; the opposite was true with bacteria.
Children who were infected with typical bacterial respiratory pathogens and those who had a mixed bacterial and viral lower respiratory infection had the most inflammation and the most severe disease. Two clinical features were strongly associated with bacterial pneumonia: high temperature (>38.4° C) within 72 hours after admission and pleural effusion. Children with a proven viral infection tended to be younger and to wheeze more often than did children with a bacterial or mixed bacterial-viral infection. The median age of children with M pneumoniae or C pneumoniae infection was 5 years and 35 months, respectivelysuggesting that preschool-aged children have at least as many episodes of atypical lower respiratory infections as older children do (Michelow IC et al: Pediatrics 2004;113:701).
Commentary: Because this study was limited to hospitalized children with pneumonia, it may not accurately reflect the profile of children seen in physicians' offices and in emergency departments, who are sent home with pneumonia. I was surprised to read that 47% of the 17 patients with atypical pneumonia were younger than 5 years. And 13% of children thought to have bacterial pneumonia alone had associated wheezing; 44% of the group had pneumococcal infection or coinfection, but these data were collected before universal pneumococcal vaccination. Information about human metapneumovirus was not collected.
Kingella kingae responsible for invasive disease cluster. A recent report describes two confirmed cases and one probable case of osteomyelitis/septic arthritis caused by K kingae among children 17 to 21 months old who were in the same classroom in a day-care center. Within one week, all three children began to run a fever, had an upper respiratory illness, and refused to bear weight on the affected limb. This report reminds pediatricians to consider K kingae infection in young children who have a Gram stain-negative or culture-negative skeletal infection (Faville R et al: MMWR 2004;53:241).