High incidence of pulmonary bacterial co-infection in children with severe respiratory syncytial virus (RSV) bronchiolitis

Respiratory syncytial virus (RSV) is the most common cause of viral lower respiratory tract infections (LRTI). Viral LRTI is a risk factor for bacterial superinfection, having an escalating incidence with increasing severity of respiratory illness. A study was undertaken to determine the incidence of pulmonary bacterial co-infection in infants and children with severe RSV bronchiolitis, using paediatric intensive care unit (PICU) admission as a surrogate marker of severity, and to study the impact of the co-infection on morbidity and mortality.A prospective microbiological analysis was made of lower airways secretions on all RSV positive bronchiolitis patients on admission to the PICU during three consecutive RSV seasons.One hundred and sixty five children (median age 1.6 months, IQR 0.5-4.6) admitted to the PICU with RSV bronchiolitis were enrolled in the study. Seventy (42.4%) had lower airway secretions positive for bacteria: 36 (21.8%) were co-infected and 34 (20.6%) had low bacterial growth/possible co-infection. All were mechanically ventilated (median 5.0 days, IQR 3.0-7.3). Those with bacterial co-infection required ventilatory support for longer than those with only RSV (p<0.01). White cell count, neutrophil count, and C-reactive protein did not differentiate between the groups. Seventy four children (45%) received antibiotics prior to intubation. Sex, co-morbidity, origin, prior antibiotics, time on preceding antibiotics, admission oxygen, and ventilation index were not predictive of positive bacterial cultures. There were 12 deaths (6.6%), five of which were related to RSV.Up to 40% of children with severe RSV bronchiolitis requiring admission to the PICU were infected with bacteria in their lower airways and were at increased risk for bacterial pneumonia.