Nasopharyngeal colonization by the Gram-positive bacterium
Streptococcus pneumoniaeis a prerequisite for pneumonia and invasive pneumococcal diseases. Colonization is asymptomatic, involving dynamic and complex interplay between commensals, the host immune system, and environmental factors. The elderly are at an increased risk of developing pneumonia, which might be due to changes in the respiratory microbiota that would impact bacterial colonization and persistence within this niche. We hypothesized that the composition of the upper respiratory tract (URT) microbiota changes with age and subsequently can contribute to sustained colonization and inefficient clearance of S. pneumoniae. To test this, we used a mouse model of pneumococcal colonization to compare the composition of the URT microbiota in young, middle-aged, and old mice in the naive state and during the course of colonization using nasal pharyngeal washes. Sequencing of variable region 3 (V3) of the 16S rRNA gene was used to identify changes occurring with age and throughout the course of S. pneumoniaecolonization. We discovered that age affects the composition of the URT microbiota and that colonization with S. pneumoniaeis more disruptive of preexisting communities in older mice. We have further shown that host-pathogen interactions following S. pneumoniaecolonization can impact the populations of resident microbes, including Staphylococcusand Haemophilus. Together, our findings indicate alterations to the URT microbiota could be detrimental to the elderly, resulting in increased colonization of S. pneumoniaeand decreased efficiency in its clearance.