The nasopharyngeal flora of smokers contains more potential pathogens and fewer bacteria with interfering capability than those of non-smokers. This paper studied the effect of smoking cessation on levels of these organisms. Two nasopharyngeal swabs were taken from 20 adults who had smoked at least 10 cigarettes a day for the previous 5 years. The first swab was taken while the patient was still smoking and the second 12–15 months after smoking cessation. None of the subjects had received antimicrobial treatment or had had a respiratory tract infection in the 3 months prior to testing.

Eleven potential pathogens were isolated from 9 of the 20 subjects before smoking cessation. Two potential pathogens were isolated from two individuals after smoking cessation (p<0.05). Bacterial interference was found in 35 instances against the four potential pathogens investigated (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and S pyogens) by 14 normal flora isolates before smoking cessation and in 116 instances by 42 isolates after smoking cessation (p < 0.01).

This study confirms previous work by the authors, that the nasopharyngeal flora of smokers contains more potential pathogens and fewer aerobic and anaerobic bacteria with interfering capability than that of non-smokers. The authors also showed that the low levels of interfering bacteria revert to normal after smoking cessation. This is an important finding, as the presence of organisms with interfering potential may play a role in the prevention of upper respiratory tract infections, and this provides further evidence for the importance of smoking cessation.