I can tell you from first hand experience, getting pneumonia is not a fun experience. It can actually be quite deadly and results in approximately 1.3 million childhood deaths each year worldwide. One of the causes of pneumonia is invasive pneumococcal disease, or a fancy way of saying a bacterial infection caused by a specific bacterium, Streptococcus pneumonia (or the pneumococcus). This bacterium often resides in the place where your mouth and nose connect called the nasopharynx. A better understanding of the relationship between this bacteria and the nasal microbiome will allow for a better ability to modulate the bacteria and prevent or treat diseases like pneumonia or meningitis.
Scientists recently published a study in the journal Microbiome that compared the nasopharyngeal microbiome of individuals who were natural carriers of this bacterium and those who were not. In a study of 40 individuals, 10 were natural carriers of the pneumococcus and 30 were not. Those who were not were inoculated (vaccinated) through their nose with one of two strains of the bacteria.
They found that the natural carriers had greater phylogenetic distances (PD) between the bacteria in their nasopharyngeal microbiome. Phylogenetic distance is a measure of how common the ancestors of specific bacteria are. Those with a greater PD had bacteria that had common ancestors a longer time ago than those with a lower PD. In individuals who were not carriers and were inoculated with the bacterial strains, those who had a more diverse microbiome resulted in pneumococcal carriage being established, meaning the presence of S. pneumonia, was identified in the nasopharynx.
This study provided a model for studying the interaction between the microbiome of our nose and specific bacteria that are important for disease onset. We often see that in an environment like the gut with a more diverse microbiome, bacteria are unable to colonize and establish a presence, but the opposite is true in this case. Those with a more diverse microbiome often had pneumococcus in their nose after inoculation. It is proposed that carriage of pneumococcus results in an immunizing event and therefore the ability for the bacteria to become established is beneficial and helps establish better immunity. Better understanding of this relationship will be important for better immunizations and preventing invasive pneumococcal disease.