Although the well-recognised predisposition of cigarette smokers to the development of severe pneumococcal disease may be attributable to impairment of local host defences, less is known about the direct effects of smoke exposure on airway pathogens, or their virulence factors. In the current study, we have investigated the effects of cigarette smoke condensate (CSC) on biofilm formation by Streptococcus pneumoniae, and on the pore-forming activity of its major toxin, pneumolysin.Biofilm formation following exposure of the pneumococcus to CSC (20-160 mg?mL -1 ) was measured using a crystal violet-based spectrophotometric procedure, while the pore-forming activity of recombinant pneumolysin was determined by a fura-2/acetoxymethyl ester-based spectrofluorimetric procedure to monitor the uptake of extracellular Ca 2+ by isolated human neutrophils. Exposure of the pneumococcus or pneumolysin to CSC resulted in significant dose-related augmentation of biofilm formation (pf0.05 at 80 and 160 mg?mL -1 ) and substantial attenuation of the pore-forming interactions of pneumolysin, respectively. Augmentation of biofilm formation and inactivation of pneumolysin as a consequence of smoking are likely to favour microbial colonisation and persistence, both being essential precursors of pneumococcal disease.

Although cigarette smoking is well-recognised as being the strongest independent risk factor for development of invasive pneumococcal disease, little is known about its direct effects on the expression of virulence factors by the pneumococcus. The primary objectives of the current study were to investigate the effects on gene expression in relation to biofilm formation following exposure of the pneumococcus to cigarette smoke condensate (CSC). Strain 172 (serotype 2-3F) of the pneumococcus was exposed to CSC (20-160 µg/ml) for 16