Isolation of pathogenic bacteria from the nasopharynx of children with respiratory syncytial virus infection. Predictive value of chest roentgen examination and laboratory tests

RSV enhances Staphylococcus aureus bacterial growth in the lung

Patients coinfected with respiratory syncytial virus (RSV) and bacteria have longer hospital stays, higher risk of intensive care unit admission, and worse outcomes. We describe a model of RSV line 19F/methicillin-resistant Staphylococcus aureus (MRSA) USA300 coinfection that does not impair viral clearance, but prior RSV infection enhances USA300 MRSA bacterial growth in the lung. The increased bacterial burden post-RSV correlates with reduced accumulation of neutrophils and impaired bacterial killing by alveolar macrophages. Surprisingly, reduced neutrophil accumulation is likely not explained by reductions in phagocyte-recruiting chemokines or alterations in proinflammatory cytokine production compared with mice infected with S. aureus alone. Neutrophils from RSV-infected mice retain their ability to migrate toward chemokine signals, and neutrophils from the RSV-infected lung are better able to phagocytize and kill S. aureus ex vivo on a per cell basis. In contrast, while alveolar macrophages could ingest USA300 post-RSV, intracellular bacterial killing was impaired. The RSV/S. aureus coinfected lung promotes a state of overactivation in neutrophils, demonstrated by increased production of reactive oxygen species (ROS) that can drive formation of neutrophil extracellular traps (NETs), resulting in cell death. Mice with RSV/S. aureus coinfection had increased extracellular DNA and protein in bronchoalveolar lavage fluid and histological evidence confirmed NETosis in vivo. Taken together, these data highlight that prior RSV infection can prime the overactivation of neutrophils leading to cell death that impairs neutrophil accumulation in the lung. Additionally, alveolar macrophage killing of bacteria is impaired post-RSV. Together, these defects enhance USA300 MRSA bacterial growth in the lung post-RSV.

Interactions between respiratory syncytial virus and Streptococcus pneumoniae in the pathogenesis of childhood respiratory infections: a systematic review

Lower respiratory tract infections, commonly caused by respiratory syncytial virus (RSV) or Streptococcus pneumoniae (pneumococcus), pose a substantial global health burden, especially in children younger than 5 years of age. A deeper understanding of the relationship between RSV and pneumococcus would aid the development of health-care approaches to disease prevention and management. We completed a systematic review to identify and assess evidence pertaining to the relationship between RSV and pneumococcus in the pathogenesis of childhood respiratory infections. We found mechanistic evidence for direct pathogen-pathogen interactions and for indirect interactions involving host modulation. We found a strong seasonal epidemiological association between these two pathogens, which was recently confirmed by a parallel decrease and a subsequent resurgence of both RSV and pneumococcus-associated disease during the COVID-19 pandemic. Importantly, we found that pneumococcal vaccination was associated with reduced RSV hospitalisations in infants, further supporting the relevance of their interaction in modulating severe disease. Overall evidence supports a broad biological and clinical interaction between pneumococcus and RSV in the pathogenesis of childhood respiratory infections. We hypothesise that the implementation of next-generation pneumococcal and RSV vaccines and monoclonal antibodies targeting RSV will act synergistically to reduce global morbidity and mortality related to childhood respiratory infections.

Respiratory syncytial virus impairs macrophage IFN-alpha/beta- and IFN-gamma-stimulated transcription by distinct mechanisms

Macrophages are the primary lung phagocyte and are instrumental in maintenance of a sterile, noninflamed microenvironment. IFNs are produced in response to bacterial and viral infection, and activate the macrophage to efficiently counteract and remove pathogenic invaders. Respiratory syncytial virus (RSV) inhibits IFN-mediated signaling mechanisms in epithelial cells; however, the effects on IFN signaling in the macrophage are currently unknown. We investigated the effect of RSV infection on IFN-mediated signaling in macrophages. RSV infection inhibited IFN-beta- and IFN-gamma-activated transcriptional mechanisms in primary alveolar macrophages and macrophage cell lines, including the transactivation of important Nod-like receptor family genes, Nod1 and class II transactivator. RSV inhibited IFN-beta- and IFN-gamma-mediated transcriptional activation by two distinct mechanisms. RSV impaired IFN-beta-mediated signal transducer and activator of transcription (STAT)-1 phosphorylation through a mechanism that involves inhibition of tyrosine kinase 2 phosphorylation. In contrast, RSV-impaired transcriptional activation after IFN-gamma stimulation resulted from a reduction in the nuclear STAT1 interaction with the transcriptional coactivator, CBP, and was correlated with increased phosphorylation of STAT1beta, a dominant-negative STAT1 splice variant, in response to IFN-gamma. In support of this concept, overexpression of STAT1beta was sufficient to repress the IFN-gamma-mediated expression of class II transactivator. These results demonstrate that RSV inhibits IFN-mediated transcriptional activation in macrophages, and suggests that paramyxoviruses modulate an important regulatory mechanism that is critical in linking innate and adaptive immune mechanisms after infection.

Radiologic differentiation between bacterial and viral lower respiratory infection in children: a systematic literature review

A systematic literature review was performed to quantify the accuracy of chest radiography in differentiating bacterial from viral lower respiratory infection in children. Relevant studies were identified in a systematic literature search and were included in the review according to predetermined criteria. Five of 13 relevant identified studies met the inclusion criteria. No clinically useful degree of accuracy was demonstrated, but great caution is needed in interpreting the findings because of the suboptimal nature of the reference standards, even in included studies. It is recommended that future surveys of the microbial etiology of pneumonia that employ a credible reference standard (such as lung aspiration) be used as opportunities to perform studies of diagnostic accuracy.

Chest X-ray appearances in pneumonia and bronchiolitis. Correlation to virological diagnosis and secretory bacterial findings

Chest X-ray findings were related to virus diagnosis, age and secretory bacterial findings in 128 infants and children under 7 years of age with clinical pneumonia and bronchiolitis. They belonged to a cohort examined in connection with the introduction of rapid methods for virological diagnosis. Seventy-six children had a virus infection diagnosed by examination of nasopharyngeal secretion and/or by serological methods. Thirty-seven of these children were classified as having pathogenic bacteria of importance in the respiratory tract. Four groups were compared: virus infected children with or without bacteria in the secretion and the corresponding virus negative groups. The X-rays were normal significantly more often in the virus positive/bacteria negative group compared with the other groups. Alveolar pneumonia appearing as lobar or segmental consolidations ("lobar" pneumonia) was observed with equal frequency and without relation to bacterial findings in the virus positive and the virus negative groups. But it was more often observed in the respiratory syncytial virus (RSV) infected children under 6 months of age compared with the older RSV children. In comparison disperse alveolar infiltrations ("bronchopneumonia") mostly appeared in the virus positive group. Interstitial pneumonia and peribronchitis were often present together in children over 6 months of age. There was no significant difference in the X-ray appearances in the groups with and without bacterial findings in the tracheal secretion except for a higher frequency of normal chest radiographs in the bacteria negative group.

Severe respiratory syncytial virus pneumonia in an adult renal transplant recipient: successful treatment with ribavirin

Respiratory syncytial virus (RSV) pneumonia may be a severe disease especially in immunocompromised patients. It is quite rare in adults. We report a case of severe RSV pneumonia in a 38-year-old male renal transplant recipient with successful outcome after ribavirin aerosol therapy.

Radiological findings in children with respiratory syncytial virus infection: relationship to clinical and bacteriological findings

Respiratory syncytial virus (RSV) is a frequent cause of bronchiolitis leading to acute admission to hospital in the winter months. A wide range of findings accompanies this disease and the appearances are seldom completely diagnostic. Associated bacterial co-infections are common and we have shown an association with atelectasis among patients with pathogenic bacteria in the nasopharynx.