Respiratory syncytial virus and bacterial co-infection of the paediatric respiratory tract — ASN Events
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Respiratory syncytial virus and bacterial co-infection of the paediatric respiratory tract (#72)

Jaelle C Brealey 1 , Keith J Chappell 1 2 , Peter D Sly 2 3 , Paul R Young 1 2
  1. School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD, Australia
  2. Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD, Australia
  3. Queensland Children’s Medical Research Institute, University of Queensland, Brisbane, QLD, Australia

Respiratory syncytial virus (RSV) is the most significant cause of acute respiratory infection (ARI) in children. The opportunistic pathogen Streptococcus pneumoniae is commonly detected during RSV infections. However, the clinical significance of these bacterial co-infections, and their effect on the host immune system, are still being elucidated. The role of RSV/S. pneumoniae co-infection was investigated in a clinical cohort and in cell culture. Nasopharyngeal aspirates from children under two years presenting with ARI at the emergency department of the Royal Brisbane Children’s Hospital were screened for respiratory viruses and bacteria. Disease severity scores were generated upon study enrolment. All 46 infants recruited to date had viral ARI, with RSV most commonly detected (54%). S. pneumoniae was more frequently detected in RSV infections (60%) compared to other viral infections (35%). Respiratory viruses were present across the spectrum of disease severity; however, S. pneumoniae detection was significantly associated with increased severity scores, regardless of RSV presence. These results suggest that in this severely ill cohort, S. pneumoniae was the main driver of disease severity. Given the high frequency of S. pneumoniae detection in severe RSV infections, the host innate immune response to co-infection was investigated, using clinical isolates of RSV and S. pneumoniae in immortalised human bronchial epithelial cells (BEAS-2B). RSV was found to induce a type I interferon response early during co-infection, while S. pneumoniae activated NF-κB signaling. The simultaneous activation of two distinct innate immune pathways by co-infection may lead to synergistic stimulation of downstream processes, such as inflammation, perhaps contributing to enhanced morbidity. The consequences of this simultaneous activation on the host are being investigated currently. Further sample collection and investigation of immune pathways should clarify the interactions between RSV and S. pneumoniae. Understanding the roles of virus and bacteria will potentially reveal novel treatment and prevention strategies for paediatric ARI.

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