Bacterial colonization and life-threatening respiratory syncytial virus infection in children.

BACKGROUND

Respiratory syncytial virus is a major cause of acute respiratory infection in children. While most cases are mild, some progress to life-threatening disease. The role of bacterial colonization in shaping respiratory syncytial virus outcomes remains incompletely understood.

OBJECTIVE

To evaluate the association between respiratory tract bacterial colonization and respiratory syncytial virus disease severity in children.

STUDY

DESIGN

Prospective cohort study conducted during 2019 and 2023. Children ≤ 24 months hospitalized with confirmed positive respiratory syncytial virus infection were enrolled. Clinical and epidemiological data were collected. respiratory syncytial virus subtypes, viral load, and detection of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis were determined by qPCR.

RESULTS

401 patients were hospitalized with acute respiratory infection, of which 172 (42.9 %) had confirmed respiratory syncytial virus infection. Among them, 15 (8.7 %) developed life-threatening disease. Bacterial colonization was highly prevalent (92.4 %): H. influenzae (68 %), S. pneumoniae (64.5 %), and M. catarrhalis (52.9 %). M. catarrhalis colonization was associated with mild disease (p = 0.003), while H. influenzae showed a trend toward increased severity (p = 0.054). Viral subtype and viral load were not linked to severity. Household crowding was independently associated with more severe disease (p = 0.031).

CONCLUSIONS

Our results support the growing evidence that airway microbiota modulates respiratory syncytial virus outcomes and highlights M. catarrhalis as potential microbial determinant of disease progression.