An in vitro study of the exposure of mixed populations of normal oropharyngeal bacteria to cigarette smoke.

Mixed populations of freshly isolated oropharyngeal bacteria growing in dextrose broth at 37 degrees C were subjected to smoke from four cigarettes over a 3 h period. Each cigarette, a commercially available brand, contained 23.0 mg of tar and 1.4 mg of nicotine. At hourly intervals eight puffs of smoke from a cigarette were passed over a 1.0 ml suspension of bacteria dispersed in a thin layer in a sterile tissue culture flask. Normal filtered air was in contact with the suspension between smoke treatments. Exposure to cigarette smoke resulted in a marked decrease in numbers of viable bacteria. Non-filter cigarette smoke had a greater detrimental effect than smoke from filter-tipped cigarettes. The predominant bacteria, non-haemolytic streptococci, and less numerous bacteria such as staphylocci, were equally sensitive to the toxic action of cigarette smoke.