Cigarette smoke exposure promotes bacterial colonization of the upper-respiratory tract

Recurrent bacterial infections of the respiratory tract contribute to the progression of the Chronic Obstructive Pulmonary Disease (COPD). There is evidence that exacerbations of COPD are provoked by new bacterial strains acquired from the environment. Using a murine model of colonization, we show that chronic exposure to cigarette smoke promotes nasopharyngeal colonization with bacterial pathogens of the lung. Nontypeable Haemophilus influenzae (NTHi) only marginally colonized air exposed mice and exposure to cigarette smoke resulted in significantly increased numbers of viable NTHi in the upper respiratory tract. Enhanced colonization levels of Streptococcus pneumoniae in the upper respiratory tract of smoke exposed mice were accompanied by increased bacterial translocation into the lung. Colonization levels in the upper respiratory tract correlated with an increased influx of immune cells into the upper respiratory tract and into the lung. These findings demonstrate that exposure to cigarette smoke impacts the ability of the host to control bacterial colonization resulting in an enhanced susceptibility of the host to potential pathogens.