Streptococcus milleri Group Pleuropulmonary Infection in Children

Abstract

Streptococcus milleri group streptococci have recently been increasingly recognized as important pulmonary pathogens, but their imaging features have not been well documented in children. We have recently observed a number of cases of this infection among pediatric patients at our tertiary care, children's hospital. Our purpose was to investigate the computed tomographic (CT) findings and clinical features of S. milleri group pleuropulmonary infection in children. We used our hospital information system to identify all consecutive pediatric patients (<18 years of age) who had both a microbiologically proven S. milleri group infection and a chest CT scan between December 1996 and May 2009. Each scan was systemically reviewed by 2 pediatric radiologists for pleural and lung parenchymal abnormalities. Pleural effusions were classified as either simple or complex and correlated with results of pleural fluid analysis. Computed tomographic findings were compared with chest radiographic findings in the subset of patients who underwent radiography within 24 hours of CT. Microbiological data, risk factors, immune status, patient management, and clinical outcome were systematically reviewed. The final study cohort consisted of 15 children (6 boys and 9 girls), ranging in age from 4.2 years to 17.7 years (mean, 10.8 years). All patients were immunocompetent without recognized risk factors for this infection. Thirteen pleural effusions were identified in 10 (67%) of the 15 patients, including 10 complex and 3 simple pleural effusions. All complex effusions at CT were consistent with empyemas by pleural fluid analysis. Lung parenchymal abnormalities were identified in 7 (47%) of the 15 patients, including lung abscess in 4 patients, consolidation in 2, and multiple bilateral pulmonary nodules and lung abscesses in 1. In the subset of 7 patients with comparison radiographs, radiographic and CT findings were concordant for the detection of lung abnormalities, except one case in which consolidation was diagnosed on chest radiography, whereas CT scan showed a lung abscess. Radiographs detected all 4 complex pleural effusions seen on CT scan, although it was not possible to characterize the effusions as simple or complex on the radiographs. Interventional procedures were required in all 15 patients, most commonly thoracentesis (n = 11) and chest tube drainage (n = 9). In children with S. milleri group pleuropulmonary infection, CT often demonstrates complex pleural effusions and lung abscesses, which usually require interventional procedures for effective treatment.