Association between smoking and presence of mycoplasma pneumoniae in circulating leukocytes

The morbidity and mortality of infectious diseases due to smoking are not widely appreciated by physicians. However, cigarette smoking appears to be a major risk factor for respiratory tract and other systemic infections. Only limited data are available on the association between smoking and Mycoplasma (M) pneumoniae. We raise the question of whether smoking increases the presence of M pneumoniae in circulating leukocytes. Furthermore we have studied whether the combination of smoking and M pneumoniae infection affects circulating levels of inflammatory biomarkers.

Prevalence of latent M pneumoniae infection was analysed in a total of 122 subjects by polymerase chain reaction. Smoking status was documented at presentation. Circulating levels of c-reactive protein, macrophage chemoattractant protein-1 and complement factor 5a were determined by commercial enzyme linked immuno-sorbent assays.

We found a significant association between smoking and latent M pneumoniae infection (p = 0.009). This association remained significant after correction for age, gender and diabetes (OR 3.4; 95% CI 1.3-9.4; p = 0.017). There was no correlation between circulating levels of the inflammatory biomarkers studied and smoking or M pneumoniae infection, respectively.

Our data indicate that smoking is associated with the presence of M pneumoniae in circulating leukocytes. This could contribute to the pro-inflammatory effects of smoking. Despite the low number of subjects included in this study, this is an interesting finding demanding further investigation.