The bacteria Streptococcus pneumoniae harmlessly colonizes the mucous linings of throats and noses in most people, becoming virulent only when they and enter the middle ears, lungs, or bloodstream. In research published in mBio, University at Buffalo researchers reveal how that happens.
Lead author Anders P. Hakansson, PhD, and his colleagues had previously found that when the pneumococci colonize the nose, they form sophisticated, highly structured biofilm communities.
In the current study, the research team grew biofilms of pneumococci on top of human epithelial cells, where the bacteria normally grow. They then infected these bacteria with influenza A virus or exposed them to the conditions that typically accompany the flu, including increased temperature to mimic fever, increased concentrations of ATP (the energy molecule in cells), and the stress hormone norepinephrine, released during flu infection.
All three stimuli triggered a sudden release and departure of bacteria from the biofilm in the nose into otherwise normally sterile organs, such as the middle ears and lungs, or into the bloodstream. At the same time, the researchers found that the gene expression profile of the bacteria that had dispersed from the biofilms revealed far more virulence.
Hakansson says the research demonstrates how the mammalian and bacterial kingdoms interact. “Humans are the only natural hosts for these bacteria,” he explains. “When the viral infection comes in, there is inter-kingdom signaling: the bacteria respond to host molecules. If we can find ways to interrupt that signaling, we might be able to prevent disease.” Read the study.
