Coinfections in Hospitalized Children With Community-Acquired Pneumonia: What Does This Mean for the Clinician?

Community-acquired pneumonia (CAP) is one of the most common infections in children admitted to the hospital [1]. The leading pathogens causing CAP in hospitalized children are respiratory viruses, including influenza virus, respiratory syncytial virus (RSV), and human metapneumovirus; bacterial pathogens such as Streptococcus pneumoniae and Staphylococcus aureus; and the atypical bacterium Mycoplasma pneumoniae. In the prospective Etiology of Pneumonia in the Community (EPIC) study, investigators from the Centers for Disease Control and Prevention, along with those from children’s hospitals in Nashville, Memphis, and Salt Lake City, determined the etiology of radiographically proven CAP in >2200 hospitalized children from January 2010 through June 2012 [2]. An etiology was proven or implied for 81% of children, using standard microbiologic culture, serologic techniques, and molecular testing. Viral etiologies were primarily implied on the basis of findings from molecular testing of nasopharyngeal specimens, which may or may not reflect the true pathogen causing the lower respiratory tract infection, especially cases due to human rhinovirus. As expected, viral etiologies were most common, with ≥1 virus detected in 66% of patients, whereas typical-bacterial pathogens (primarily S. pneumoniae) were identified in 8%. Evidence of M. pneumoniae infection was found in 8% of patients. Multiple pathogens were detected in 26%, both bacteria and viruses in 7%, and multiple viruses in almost 20%, particularly in children <5 years of age. The interactions of viruses and bacteria in the pathogenesis of both local and invasive respiratory tract infections have been studied for many years. The mechanisms by which preceding influenza virus infections lead to a secondary bacterial infection with S. aureus or S. pneumoniae have been of particular interest [3–5]. In this issue of The Journal of Infectious Diseases, Nolan et al [6] examined the EPIC database to further understand the impact of copathogens on the clinical manifestations and outcome of CAP in hospitalized children. As noted above, 26% of children (576 of 2219) had coinfections detected. Of great interest were the 99 children who had ≥1 virus and ≥1 typical bacterium identified. RSV and human rhinovirus were the viruses found most often as single pathogens and were also the viruses most commonly found as copathogens with other viruses or bacteria. S. pneumoniae was codetected with RSV in 11 patients, parainfluenza virus and coronavirus in 8 each, human metapneumovirus in 7, and influenza virus in 4. S. aureus was identified with ≥1 virus in 13 children. M. pneumoniae was a copathogen with ≥1 virus, most commonly human rhinovirus (n = 18), influenza virus (n = 6), and RSV (n = 4), in 48 children. However, demographic and clinical characteristics of children with CAP, including age, underlying conditions, duration of illness prior to admission, prevalence of cough, prevalence of fever, prevalence of chest retractions, and chest radiography findings at admission, were not different between children with typical bacteria alone and those with viral and typical bacterial copathogens or between children with M. pneumoniae alone and those with M. pneumoniae and viral copathogens. Not unexpectedly, children with typical bacteria alone or with viral and typical bacterial copathogens were more likely than children with viruses alone to have a consolidation pattern on their admission chest radiograph or a parapneumonic effusion sometime during hospitalization. There was 1 difference noted for virus-virus coinfections as compared to single-virus infections, with higher rates of supplemental oxygen use in the first 24 hours of hospitalization in the group with virus-virus copathogens. In an earlier study from Dallas, clinical characteristics (pneumonia was most common) were not significantly different among 129 children with invasive pneumococcal disease (IPD) with (n = 28) or without (n = 101) a viral coinfection [5]. E D I T O R I A L C O M M E N T A R Y