Microbiome composition influences severity of Legionnaires’ illness

Pneumonia is an an infection of the lung alveoli attributable to micro organism, viruses or fungi. It is likely one of the main causes of morbidity and mortality worldwide, representing a scientific and financial burden and a world public well being drawback. The microbial ecosystem (or microbiome) of the human respiratory tract colonizes totally different niches. The respiratory tract microbiome is of curiosity to scientists because it contributes to human well being by stimulating the immune system and defending towards an infection by pathogens. Scientists from the Institut Pasteur and the CNRS have demonstrated that the microbiome composition, pathogen load and scientific interventions affect the severity of bacterial pneumonia attributable to Legionella pneumophila. The outcomes have been printed within the journal Cell Studies Medication on August 25, 2023.

On this examine, scientists from the Biology of Intracellular Micro organism Unit, led by Carmen Buchrieser on the Institut Pasteur, in collaboration with Sophie Jarraud, Head of the Nationwide Reference Middle for Legionella in Lyon, analyzed the variety and composition of the respiratory tract microbiome (micro organism, archaea, fungi and protozoa) in sufferers with pneumonia attributable to the intracellular bacterial pathogen Legionella pneumophila for his or her total hospitalization interval. L. pneumophila is liable for a extreme pneumonia referred to as Legionnaires’ illness, which will be contracted by inhaling contaminated aerosols from synthetic water sources corresponding to showers, scorching tubs or air-con techniques. The fatality fee for Legionnaires’ illness varies from 5 to 40% relying on the scientific context and the area. Threat components are previous age, pre-existing lung situations, smoking and immunosuppression, and round two-thirds of reported instances happen in males. Confirmed instances of Legionnaires’ illness within the European Union went from 4,693 instances in 2005 to 10,004 instances in 2021, a rise of 113%. One of many causes for this sharp rise could also be local weather change, with larger water temperatures and extra frequent and intense floods that enable Legionella to duplicate extra quickly and to entry human environments.

The group of scientists mixed high-throughput bacterial, archaeal and fungal marker gene sequencing with a quantification method to characterize how the respiratory tract microbiome developed in sufferers over the course of an infection and on account of hospital-related interventions (corresponding to mechanical air flow and administration of antibiotics). A singular cohort of 38 hospitalized sufferers with pneumonia attributable to Legionella pneumophila was analyzed. «We found complicated microbiome dynamics, the place commensal and pathogenic microorganisms coexist, and the equilibrium amongst their abundance drives the microbiome to restoration or dysbiosis,» explains Carmen Buchrieser, lead writer of the examine and Head of the Institut Pasteur’s Biology of Intracellular Micro organism Unit. The scientists noticed that early in hospitalization, microbiome range decreased and the pathogen L. pneumophila was killed by the antibiotic remedy. However the empty area of interest was quickly occupied by different opportunistic species, usually proof against antimicrobials – an element that must be thought-about in prevention methods for secondary infections. The respiratory tract microbiomes with the best bacterial and fungal hundreds additionally confirmed decrease range and pathogen enrichment, indicating that prime biomass could possibly be a biomarker for secondary and/or co-infections. Lastly, the scientists confirmed that Legionella biomass correlates with illness severity and comorbidities, suggesting that pathogen quantification must be included in affected person monitoring. Medical interventions corresponding to mechanical air flow or administration of sure sorts of antibiotics affect the microbiome composition and due to this fact additionally illness end result.

On this examine we additionally found that fungi, archaea and protozoa could also be resident and never merely transitory within the respiratory tract of hospitalized sufferers and that they may contribute to pneumonia development. This requires additional investigation. Our analysis due to this fact exhibits that the interplay between respiratory tract microbiome equilibrium, pathogen load dynamics and scientific interventions performs an important position within the restoration of sufferers with pneumonia.»

Carmen Buchrieser, Institut Pasteur