Increased Nasopharyngeal Bacterial Titers and Local Inflammation Facilitate Transmission of Streptococcus pneumoniae

The transmission of the bacterium Streptococcus pneumoniae (the pneumococcus) marks the first step toward disease development. To date, our ability to prevent pneumococcal transmission has been limited by our lack of understanding regarding the factors which influence the spread of this pathogen. We have previously developed an infant mouse model of pneumococcal transmission which was strictly dependent on influenza A virus (IAV) coinfection of both the experimentally colonized “index mice” and the naive cohoused “contact mice.” Here, we sought to use this model to further elucidate the factors which facilitate S. pneumoniae transmission. In the present report, we demonstrate that increasing the nasopharyngeal load of S. pneumoniae in the colonized index mice (via the depletion of neutrophils) and inducing a proinflammatory response in the naive cohoused contact mice (as demonstrated by cytokine production) facilitates S. pneumoniae transmission. Thus, these data provide the first insights into the factors that help mediate the spread of S. pneumoniae throughout the community.