Viability of six species of normal oropharyngeal bacteria after exposure to cigarette smoke in vitro.

Bacteria in culture medium at 37 degrees C were subjected to eight puffs of smoke from one cigarette, and viable cell counts were done at intervals ranging from 0 min to 3 h after exposure to smoke. The cigarette contained 23.0 mg of tar and 1.4 mg of nicotine. Each 25.0 ml puff of smoke from a mechanical smoking apparatus was passed over a 1.0 ml suspension of bacteria dispersed over a 25 cm2 surface in a sterile flask. Filtered air was in contact with the suspension between puffs, and during the intervals between smoke treatment and viable cell counts being done. There was a marked decrease in numbers of viable Branhamella catarrhalis at 15 min after exposure to smoke, and by 1 h there were no viable cells in suspensions which originally contained 10(7) bacteria. No reduction in the number of viable Branhamella catarrhalis occurred in an untreated suspension of the micro-organism. There was a marked decrease in viable Neisseria perflava at 30 min, and by 3 h there were no viable cells. There was a 4 to 5 log10 reduction of viable Neisseria sicca compared with untreated bacteria at 3 h after exposure to smoke. Streptococcus mitis, Streptococcus salivarius, and Streptococcus sanguis were less susceptible to the harmful action of cigarette smoke, and by 3 h there were 1 to 2 log10 differences in viable cell counts between smoke-treated and untreated bacteria. Non-filter cigarette smoke had a greater detrimental effect on all species of bacteria studied than smoke from filter-tipped cigarettes.