How Is Bacterial Pneumonia Impacted by Our Respiratory Microbiome?
The respiratory microbiome can protect against pathogens, but how does it influence the severity of bacterial pneumonia?
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Pneumonia is an infection of the lung alveoli caused by bacteria, viruses or fungi. It is one of the leading causes of morbidity and mortality worldwide, representing a clinical and economic burden and a global public health problem. The microbial ecosystem (or microbiome) of the human respiratory tract colonizes different niches. The respiratory tract microbiome is of interest to scientists as it contributes to human health by stimulating the immune system and protecting against infection by pathogens. Scientists from the Institut Pasteur and the CNRS have demonstrated that the microbiome composition, pathogen load and clinical interventions influence the severity of bacterial pneumonia caused by Legionella pneumophila. The results were published in the journal Cell Reports Medicine on August 25, 2023.
In this study, scientists from the Biology of Intracellular Bacteria Unit, led by Carmen Buchrieser at the Institut Pasteur, in collaboration with Sophie Jarraud, Head of the National Reference Center for Legionella in Lyon, analyzed the diversity and composition of the respiratory tract microbiome (bacteria, archaea, fungi and protozoa) in patients with pneumonia caused by the intracellular bacterial pathogen Legionella pneumophila for their entire hospitalization period. L. pneumophila is responsible for a severe pneumonia known as Legionnaires' disease, which can be contracted by inhaling contaminated aerosols from artificial water sources such as showers, hot tubs or air conditioning systems. The fatality rate for Legionnaires' disease varies from 5 to 40% depending on the clinical context and the region. Risk factors are old age, pre-existing lung conditions, smoking and immunosuppression, and around two-thirds of reported cases occur in men. Confirmed cases of Legionnaires' disease in the European Union went from 4,693 cases in 2005 to 10,004 cases in 2021, an increase of 113%. One of the reasons for this sharp rise may be climate change, with higher water temperatures and more frequent and intense floods that allow Legionella to replicate more rapidly and to access human environments.
"In this study we also discovered that fungi, archaea and protozoa may be resident and not merely transitory in the respiratory tract of hospitalized patients and that they might contribute to pneumonia progression. This requires further investigation. Our research therefore shows that the interaction between respiratory tract microbiome equilibrium, pathogen load dynamics and clinical interventions plays a crucial role in the recovery of patients with pneumonia," concludes Carmen Buchrieser.
Reference: Pérez-Cobas AE, Ginevra C, Rusniok C, Jarraud S, Buchrieser C. The respiratory tract microbiome, the pathogen load and clinical interventions define severity of bacterial pneumonia. Cell Rep Med. 2023. doi: 10.1016/j.xcrm.2023.101167
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