Researchers report in Science Immunology that a specific gut microbe can protect mice from deadly bacterial pneumonia that follows influenza A infection. The team focused on segmented filamentous bacteria (SFB), a gut microbe present in some mammals, and tested whether SFB altered susceptibility to secondary bacterial infection after influenza.
In the experiments, mice infected with influenza A were exposed to common respiratory pathogens: Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus. Mice carrying SFB showed marked protection against these otherwise highly lethal secondary infections. The authors note that much illness and many deaths during influenza pandemics come from such secondary bacterial infections, so gut microbiota composition could influence survival in severe outbreaks.
The protective effect depended on alveolar macrophages in the lung. Although SFB lives only on the outer surface of the intestine, it epigenetically reprogrammed those macrophages so they resisted influenza-induced dysfunction and maintained strong defence against respiratory bacteria. Lead author Vu Ngo emphasised how adding one species changed macrophage responses, and senior author Andrew T. Gewirtz said they hope to harness this mechanism to create new pharmacologic approaches to reduce the severity of many respiratory infections. The study was funded by the National Institute of Allergy and Infectious Diseases of the NIH.
- Key organism: segmented filamentous bacteria (SFB)
- Main mechanism: epigenetic reprogramming of alveolar macrophages
- Implication: gut microbiota may affect influenza outcomes
Difficult words
- segmented filamentous bacteria — a specific type of gut bacterium found in mammals
- epigenetic — relating to changes in gene activity without DNA changeepigenetically
- alveolar macrophage — immune cell in lung air sacs that eats pathogensalveolar macrophages
- susceptibility — likelihood of being affected by a disease
- gut microbiota — the community of microorganisms living in the gut
- pathogen — a microorganism that can cause disease in hostspathogens
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Discussion questions
- How might differences in gut microbiota composition influence survival during severe influenza outbreaks?
- What are possible benefits and risks of using a single gut microbe to reduce the severity of respiratory infections?
- What additional experiments would you want to see before trying this approach in humans?
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