Researchers from the Centre for Infection and Immunity in Lille (CNRS/Inserm/Institut Pasteur de Lille/University of Lille/CHU Lille) and their colleagues from INRAE have revealed for the first time in mice that disturbances in the intestinal microbiota caused by the influenza virus favour secondary bacterial superinfections. Published in the US journal Cell Reports on March 3, 2020, these results offer new insights into the prevention and treatment of bacterial pneumonia, a major cause of death in elderly or vulnerable people infected with influenza virus and coronavirus.
Influenza and its complications remain a major public health problem and a heavy socio-economic burden. Vaccination campaigns and the discovery of new antiviral treatments offer preventive or therapeutic solutions. However, the impairment of defence mechanisms against secondary bacterial infections, which considerably worsen the clinical picture of people with influenza, remains a major problem.
Specializing in the field of pulmonary immunity, the team led by François Trottein, a CNRS researcher at the Centre d'infection et d'immunité de Lille (CNRS/Inserm/Institut Pasteur de Lille/Université de Lille/CHU Lille), is interested in the intestinal microbiota, well known for its key role in many physiological processes, including immune defence mechanisms.
Scientists have shown, in mice, that influenza transiently alters the composition and metabolic activity of the intestinal microbiota, probably due to reduced food consumption during illness. During influenza, the production of short-chain fatty acids by the bacteria of the microbiota is also reduced. These are small molecules produced by bacteria, which are able to pass from the intestine to the general circulation and to immune cells in the lung alveoli. These short-chain fatty acids (SCFAs) are produced in the gut by certain bacteria of the microbiota during the fermentation of plant fibres.
The research team reveals that these fatty acids remotely promote the bactericidal activity of macrophages in the lungs. The disruption of the intestinal microbiota by influenza thus compromises the lung's defences, in particular against Streptococcus pneumoniae, the leading cause of bacterial pneumonia in humans.
Researchers have also shown that this sensitivity to bacterial superinfection can be corrected by treatment with acetate, one of the main short-chain fatty acids produced by the microbiota.
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This work could have concrete applications for the well-being of infected patients who would be better equipped to deal with influenza-related complications. This discovery, made in collaboration with scientists from the Institut Micalis (INRAE/AgroParistech/University Paris Saclay), the Lille inflammation research international center (Inserm/University of Lille/CHU Lille), the Laboratory for the Design and Application of Bioactive Molecules (CNRS/University of Strasbourg), the Molecular Virology and Immunology Unit (INRAE) and GenoScreen (Lille), represents a major advance in understanding the mechanisms leading to bacterial superinfections in influenza patients. It could lead to the development of new nutritional and/or therapeutic strategies aimed at better controlling bacterial infections.
Diet to strengthen your defences against influenza (and coronavirus)
Thus, it appears that increasing the consumption of plant fibres in times of influenza epidemics could help protect against the infectious complications of influenza. Similarly, fasting and calorie restrictions should be avoided and are not advisable during these epidemic episodes.
To protect her intestinal microbiota during an influenza epidemic, British immunologist Sheena Cruickshank proposes in The Guardian eat a balanced diet of foods high in fibre. It is found in legumes (soybeans, lentils, chickpeas, dried beans), whole grains (rice, bread, pasta, oats ...), or some fruits and vegetables (cooked cauliflower, endive, raspberry, pumpkin ...). It would also be recommended to eat fermented products such as yoghurt, sauerkraut or kimchi (traditional Korean dish made of chilli peppers and lacto-fermented vegetables).
To go further :
- " Discovering the belly and its bacteria - A path of vitality "by Marcel Roberfroid - Edition Josette Lyon, October 2019