Seroprevalence of chronic Chlamydia pneumoniae infection in patients affected by chronic stable asthma

Objective To evaluate the seroprevalence of Chlamydia pneumoniae and age, gender and smoking habits in stable asthmatic patients. Methods Over a period of 3 months, 197 adult patients affected by intermittent-to-severe chronic asthma were enrolled from 16 respiratory disease units in the south of Italy. As a control group, we tested 185 healthy, non-asthmatic subjects matched for age and gender, recruited among hospital staff. All patients were submitted to clinical examination, spirometry and blood collection for C. pneumoniae serology. The presence of infection was investigated by microimmunofluorescence (Micro-IF Test) for C. pneumoniae -specific IgG, IgM and IgA antibodies. Results C. pneumoniae IgG titers greater than or equal to1 : 64 were detected in 30.4% of asthmatics and in 30.8% of controls. Correlation of age, gender and smoking habit with C. pneumoniae seropositivity was evaluated by linear regression analysis. Age was significantly associated with C. pneumoniae IgG titer greater than or equal to1 : 64 when seropositive asthmatics were tested. Moreover, C. pneumoniae seroprevalence was higher among smokers with a diagnosis of chronic asthma. Conclusions The seroprevalence of C. pneumoniae in stable asthmatics was comparable with the controls; therefore, the study does not support the association between C. pneumoniae antibody titers and stable asthma. However, the analysis for likely confounders such as age, gender and smoking status suggests a possible association of enhanced susceptibility to C. pneumoniae infection with age and smoking habitus.