Pneumococcal pneumonia—is it underdiagnosed?

Abstract

To the Editor: Cevey-Macherel et al. published in the journal their very interesting results on the etiology of community-acquired pneumonia (CAP) by the World Health Organization (WHO) criteria in 99 hospitalized children aged 2 months to 5 years [1]. An extensive test panel was in use including antigen detection and antibody assays for seven viruses and polymerase chain reaction (PCR) for 13 viruses. PCR and conventional serology were available for Mycoplasma pneumoniae and Chlamydia pneumoniae. Streptococcus pneumoniae was studied by PCR for the pneumolysin gene in whole blood and by IgG antibodies to pneumolysin in paired sera. Bacterial infection was identified in 19%, viral in 33%, and mixed viral-bacterial in 33%, without any significant association with the WHO severity classification. S. pneumoniae caused 45% of the cases [1]. High antibody titers were regarded diagnostic, though they are merely an indication of an earlier infection. However, IgG to pneumolysin found only 4/27 (14.8%) of serologically diagnosed pneumococcal CAP cases of <5 years old children in our population-based study [2], and half of them were hospitalized. Though the value of pneumococcal antibody assays has been questioned, the real proportion of S. pneumoniae in hospitalized CAP cases probably is even greater than 45% identified [1]. M. pneumoniae and/or C. pneumoniae were found by PCR in <10% and by antibodies in 12/71 (17%) of the CAP cases [1]. In our population-based study, M. pneumoniae and/or C. pneumoniae caused 15/105 (14%) of CAP cases in <5 years old children [3], when conventional serology was supplemented by enzyme immunoassay. Both sole pneumococcal etiology and mixed etiology with viruses or atypical bacteria are common in CAP in children <5 years old [1]. The previously rare CAP complications like necrotizing pneumonia and empyema are increasing, being usually caused by S. pneumoniae. Which children with pneumonia—if any—could safely withheld antibiotics, and how they should be monitored, remains to be resolved in future.