Sole pathogen in acute bronchiolitis: is there a role for other organisms apart from respiratory syncytial virus?

Acute bronchiolitis (AB) is a common disease of young children with peak incidence during the winter season. Respiratory syncytial virus (RSV) is a major causative organism, yet recent relatively small sized studies have suggested an increased role of other organisms as sole or codetected organisms. The aim of this study was to assess the prevalence of sole- and mixed-organisms infections in hospitalized children with AB, using combined antigen-based and polymerase chain reaction assays (PCR). Sputum or nasal wash specimens obtained from 490 previously healthy children < or =2 years of age hospitalized with AB between December 1, 2005 and March 31, 2006 were tested: (1) For RSV, by rapid antigen detection test; (2) For RSV, influenza A, B, Parainfluenza 1 to 3, and adenovirus antigens by direct fluorescent assay; (3) For influenza A and B, RSV, Parainfluenza 1 to 3 viruses RNA by reverse transcription (RT) PCR assay; (4) For human metapneumovirus and rhinovirus RNA by RT real-time PCR assay; (5) For adenovirus, and Bordetella pertussis DNA by conventional PCR assays; (6) For human bocavirus DNA by real-tine PCR assays. At least 1 organism was detected in 465 (91%) children. In 283 (61%), 117 (25%), and 23 (5%) children, 1, 2, and 3/4 organisms were detected, respectively. The most commonly detected organism was RSV, detected in 76%, and as a sole organism in 49%. Rhinovirus, human metapneumovirus, influenza virus A, bocavirus, Bordetella pertussis, and adenovirus were detected as a sole organism in 7%, 2.1%, 1%, 0.6%, 0.6%, and 0.2% of the children, respectively. Respiratory organisms were detected in the majority of the children, of whom about one third suffered from mixed organism infection. RSV was the most prevalent sole detected organism. The relevance of all other organisms may be much less than previously suggested.