New research shows that altered bacterial balance in the oropharynx may amplify the impact of Influenza A. A new study published in mSystems, a journal of the American Society for Microbiology, reveals that cigarette smoke damages the lungs and disrupts the delicate balance of bacteria in the throat—an effect that may significantly worsen the severity of influenza A virus infections.
Scientists from the University of Bern in Switzerland have found that cigarette smoke can induce a disordering of the oropharyngeal microbiota. This region includes the back of the tongue, tonsils, soft palate, and upper throat. The disruption caused by smoking may play a key role in how the body handles viral infections such as the flu.
Microbiota Transfer Sheds Light on Infection Pathways
To examine the effects of smoking on the microbiota and its potential influence on flu severity, researchers conducted a controlled study using mice. Some mice were exposed to cigarette smoke, while others were kept in clean air. The researchers then transferred bacteria from the exposed and non-exposed mice into germ-free mice—animals raised without any existing microbiota.
After colonization, all mice were infected with the influenza A virus. The results were precise: mice that received bacteria from smoke-exposed donors experienced significantly more severe illness, including increased weight loss. These mice had never been exposed to smoke directly, indicating that the altered microbiota alone was capable of exacerbating the disease.
Flu Virus Further Alters Bacterial Balance
In addition to the effects of cigarette smoke, the researchers found that the influenza virus caused notable changes in the oropharyngeal microbiota—particularly noticeable on days 4 and 8 post-infection. This suggests a compounding effect, where smoking initially disrupts the bacterial environment, and the virus accelerates the imbalance during infection.
“This study shows that it is not only the smoking per se that impacts respiratory disease,” said Dr. Markus Hilty, lead author and associate professor at the Institute for Infectious Diseases at the University of Bern. “Our data indicate that the smoker’s microbiota may also impact respiratory disease and/or infection. In our case, it impacts viral infection.”
New Factor in Cigarette Smoke and Disease Management
The findings underscore the importance of considering microbial composition in the oropharynx when evaluating the health risks associated with smoking. While the damaging effects of cigarette smoke on the lungs and cardiovascular system are well-documented, this study adds a new layer: long-term microbial disruption that can intensify the body’s response to viral threats.
By highlighting how cigarette-induced microbial changes contribute to infection severity, the research offers new insight into the complex interactions between environmental exposures, microbiota, and disease. This area may hold potential for future preventative or therapeutic strategies.
Reference: Tsering Wüthrich, Simone de Brot, Veronica Richina, Nadja Mostacci, Zora Baumann, Nathan G. F. Leborgne, Aurélie Godel, Marco P. Alves, Mohamed Bentires-Alj, Charaf Benarafa, Markus Hilty. Cigarette smoke-induced disordered microbiota aggravates the severity of influenza A virus infection. mSystems, 2024.
