Some lactic acid bacteria have developed an amazing ability to colonize the nose. This nasal microbiota is believed to play an important role in preventing respiratory disease and allergies by attacking other pathogenic microbes.
Everyone knows today about intestinal microbiota, the microbial organisms that inhabit our intestines, and is believed to play an essential role in immunity, obesity, cardiovascular disease, allergies, anxiety, and even athletic performance. Recently it has also been discovered that there is a microbiota of the skin and a microbiota of the tongue. We now know that we also have a nasal microbiota. Better still, this nasal microbiota can protect us from respiratory diseases such as chronic sinusitis and allergies.
Lactic acid bacteria in the nose
In a study published in Cell Reports, biologist Sarah Lebeer and her colleagues at the University of Antwerp in Belgium looked for bacteria in the noses of 100 healthy people and compared them to 225 patients with chronic sinusitis and nasal disease. Among the 30 families of bacteria found in the nose, they identified one that is particularly common in healthy volunteers: Lactobacillus Casei. These bacteria are three times more numerous in the anterior nasal cavity and ten times more numerous in the nasopharynx in healthy subjects. 40% of the unhealthy subjects did not have any L. Casei in their upper airways.
Unique adaptation to the nasal environment
This discovery is all the more surprising because L. Casei, a lactic acid bacterium found mainly in fermented milk, often thrives in oxygen-deficient environments with carbohydrate-containing substrates such as the intestinal mucosa. This is the opposite of the nose, where the air is constantly circulating. To understand this paradox, researchers sequenced the genome of L. Casei from the nose and discovered that they have special genes encoding catalase and other enzymes with antioxidant properties that give them good tolerance to oxygen. And this is not the only adaptive evolution these bacteria have developed.
Through microscopic observation, researchers have discovered that the Lactobacillus Casei in the nose have tiny hair-like fibers that anchor them firmly to the nasal mucosa. “Otherwise, the bacteria would be quickly eliminated by the mucus and nasal rinsing,” the authors explain.
A small probiotic spray in the nose
To investigate the role of Lactobacillus Casei in disease prevention, the researchers placed the specific strain of the bacteria found in the nose in the presence of other pathogenic bacteria such as Staphylococcus aureus, Haemophilus Influenzae or Moraxella Catarrhalis, which are particularly responsible for sinuses and lung infections. They found that L. Casei effectively prevents the development of pathogenic bacteria.
Based on this result, the researchers prepared a nasal spray containing strains of L. Casei, which they administered to 20 healthy volunteers in two daily doses over two weeks. This was successful because the bacteria colonized the participant’s noses quickly and without side effects.
The beneficial role of lactobacilli has been widely studied in intestinal and vaginal microbiota, but its effect on the respiratory tract remains largely unknown, the authors conclude. The administration of specific probiotics in the nose could open up a new way of treating chronic respiratory diseases.