['Although some studies indicate a low risk of serious bacterial infection in infants with respiratory syncytial virus (RSV), these studies focused on patients who did not progress to respiratory failure. We hypothesized the composite diagnosis of concomitant bacterial pneumonia (CBP) is common in lower risk infants with RSV who present in respiratory failure. The aim of the study was to investigate the incidence of CBP in low-risk infants mechanically ventilated for RSV respiratory failure and to compare the results with other studies searched for in MEDLINE.', 'Prospective, descriptive study, and literature review. Two MEDLINE searches were done using the terms 1) respiratory syncytial virus (RSV) and pneumonia, and 2) RSV, pneumonia, and antibiotics.', 'Tertiary pediatric intensive care unit (PICU) in the Northeast United States.', 'We prospectively enrolled 23 infants admitted to our PICU with RSV infection and respiratory failure over a 27-month period.', 'None.', 'All infants were intubated on arrival or soon thereafter; 22 had diagnostic tracheal aspiration performed, and 20 had blood cultures obtained shortly after admission. All had white blood cell count, temperature measured, and chest radiograph. Only one had antibiotics before culture. The length of mechanical ventilation, PICU course, and hospital stay were recorded.The primary outcome variable was the composite diagnosis of CBP as determined by the following criteria: 1) isolation of pathogenic bacteria from a tracheal aspirate, 2) blood culture, 3) chest radiograph, 4) temperature abnormality, and 5) peripheral white blood cell count. In our study, 7 infants met four criteria (probable pneumonia); 6 met three criteria (possible pneumonia); and 10 infants met less than three criteria. By tracheal aspirate criteria alone, 9 of 23 (39%) had probable pneumonia and 9 of 23 had possible pneumonia by previously published criteria. The mean length of mechanical ventilation for 7 infants who met four criteria was 10 +/- 2.7 (sem) days; for 6 infants who met three criteria, 10.5 +/- 2.1 days; and for infants who met less than three criteria 7.4 +/- 0.9 days. The mean PICU stay was 14.3 +/- 3.6 days for infants who met four criteria; 14.3 +/- 3.0 days for infants who met three criteria; and 9.9 +/- 1.4 days for infants who met less than three criteria. The mean hospital stay was 16.3 +/- 3.4 for infants who met four criteria; 18.7 +/- 2.8 days for infants who met three criteria; and 24.8 +/- 9.6 days for infants who met less than three criteria. These differences were not statistically significant. A MEDLINE search was performed using the terms 1) RSV and pneumonia, and 2) RSV, pneumonia, and antibiotics.'] Are empiric antibiotics justified for infants with respiratory syncytial virus lower respiratory tract infection presenting with respiratory failure : a prospective study and evidence review?