Titel: Establishing Colonization of Mice with Streptococcus pneumoniae to study the natural route of Influenza A virus mediated co-infections of the lower respiratory tract
Art: Abstractautor
Session: Workshop 01
Virulence Principles in Respiratory Tract Infections (FG MP)

Referent: Sebastian Skorka (Greifswald)

Abstract - Text

Introduction: Streptococcus pneumoniae is a typical colonizer of the human upper respiratory tract (URT). About 20–50% of healthy children and 8–30% of healthy adults are asymptomatically colonized. Influenza A viruses (IAV) have been identified as important pathogens that can pave the way for pneumococcal spread from the URT to the lungs causing severe medical conditions, including pneumonia. The exact mechanisms behind these bacterial and viral co-infections are still not well understood.

Objectives: Here, we aim to establish a natural route of bacterial and viral co-infections by colonizing the mice with a non-invasive pneumococcal strain before introducing the IAV to the host.

Materials & methods: First, C57BL/6J mice were colonized with S. pneumoniae 19F for seven consecutive days or infected with human-derived H1N1. Clinical conditions, weight, microbiological and immunological parameters were monitored over the whole period of infections. Second, based on the results of the single infections/colonization co-infections were performed.

Results: Nasopharyngeal pneumococcal colonization of mice resulted in a systemic and local inflammation during the first two days. All monitored values normalized by day four. Constant bacterial counts were recovered from nasopharynx over a period of seven days. Viral infections were characterized by weight loss and a shift in neutrophils/leukocytes counts systemically at day seven p.i. In addition, viral RNA was recovered from lungs of the animals. Viral infections of mice harboring pneumococci in the nasopharyngeal cavity were performed seven days post colonization. Initial monitoring of co-infected animals revealed no clinical signs of disease during the first seven days. However, initial bacterial spread to the lungs and elevated neutrophil counts in the blood stream were detected seven days post viral application.

Conclusions: Although the co-infected animals did not show critical clinical signs of pneumonia, the proposed model serves as a starting point for future experimental directions, which will include studies on synergistic effects of the pathogens in the host, systemic and local immune responses, tissue pathology, and microbiome composition.