Microorganisms associated with respiratory syncytial virus pneumonia in the adult population

Respiratory syncytial virus (RSV) has been recognized as responsible for severe respiratory illness in adults, especially in the elderly. While pneumonia is commonly observed during RSV infection, the burden and epidemiology of bacterial superinfection is poorly understood. The aim of this study was to identify microorganisms associated with RSV-positive pneumonia in adults. A retrospective study was conducted during three consecutive winters (October to April 2013-2016) in the University Hospital of Lyon, France. During RSV circulation periods, a systematic RSV screening was performed by reverse-transcription PCR on all respiratory samples collected from adults. Records of RSV-positive patients were subsequently analyzed to identify radiologically confirmed pneumonia cases. Bacteria were identified by standard bacteriology cultures or urinary antigen screening and classified as potentially causative of pneumonia if quantification was above the specific threshold as defined by the European Manual of Clinical Microbiology. Overall, 14,792 adult respiratory samples were screened for RSV detection by PCR. In total, 292 had a positive RSV detection (2.0%) among which 89 presented with pneumonia including 27 bacterial superinfections (9.3%) with Streptococcus pneumonia, Haemophilus influenza, Staphylococcus aureus, Pseudomonas aeruginosa, and Moraxella catarrhalis. Most patients were elderly (55.6%) and patients with comorbidities (77.8%). A more severe outcome was observed for RSV-bacteria-associated pneumonia compared with RSV pneumonia: length of stay was significantly longer (16 days vs 10 days) and ICU hospitalization more frequent (66.7% vs 21.0%) (p < 0.05). In conclusion, we did not observe major differences in the epidemiology of bacterial superinfections in RSV-positive pneumonia compared to reports on post-influenza pneumonia.