Cigarette smoke suppresses innate immunity of the upper-respiratory tract leading to enhanced colonization of the lung

Smoking promotes enhanced colonization of the upper and the lower respiratory tract with potential pathogens, which increases the susceptibility to pulmonary infections. Here, we examined whether smoke exposure favors colonization of the upper-respiratory tract with bacterial pathogens such as Streptococcus pneumoniae and translocation of bacteria into the lung. To investigate this, mice were exposed to cigarette smoke in a long-term-smoke model for 8 months and afterwards colonized with S. pneumoniae in the upper-respiratory tract. Smoked mice showed higher colonization levels of the upper-respiratory tract com…