Respiratory potentially pathogenic bacteria are associated with increased disease severity in neonates with respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections (LRTIs) in infants under two years of age. However, the presence of respiratory bacterial pathogens and their impact on RSV severity in neonates remains inadequately understood. We therefore investigated the profiles of respiratory potentially pathogenic bacteria (PPB) in neonates with RSV and assessed their association with disease severity. We conducted a retrospective cohort study at the Children’s Hospital of Soochow University, including neonates diagnosed with LRTIs from July 2017 to June 2024. RSV-positive cases were categorized by disease severity based on the need for oxygen support, mechanical ventilation, or NICU admission. The distribution of PPB and their clinical implications were analyzed. Among 4,091 neonates with LRTI, 542 were RSV-positive (419 non-severe, 123 severe). In RSV-positive neonates, the presence of PPB was associated with a higher incidence of high fever (P = 0.002), feeding difficulty (P = 0.019), cardiovascular complications (P = 0.048), and oxygen supplementation (P = 0.015), as well as prolonged oxygen therapy (P = 0.018) and increased NICU admission rates (P = 0.028). Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae were the most commonly detected PPB. Notably, both overall PPB presence and K. pneumoniae detection were independently associated with severe RSV infection in neonates (P = 0.013 and 0.041, respectively). PPB, particularly K. pneumoniae, play a significant role in exacerbating the severity of RSV infection in neonates. These findings highlight the necessity of considering bacterial pathogens in the clinical management of RSV infection in neonates.