Chlamydia pneumoniae infection in adult patients with persistent cough.

Chlamydia pneumoniae is a frequent causative agent of acute respiratory disease. To assess whether C. pneumoniae plays a role in persistent cough, the prevalence of C. pneumoniae infection in adult patients with persistent cough was investigated. Nasopharyngeal swabs and serology samples from 366 adult patients with a persistent cough lasting in excess of 2 weeks and 106 control subjects were analysed for bacterial isolation and by PCR. C. pneumoniae was isolated from two patients and from none of the controls and was detected by PCR in 20 patients and one control. Serological evidence of acute C. pneumoniae infection was present in 24 patients but in none of the controls. Of these 20 patients who were positive by culture and/or PCR, three were still positive by PCR after 2 weeks of treatment with clarithromycin and symptoms either continued or relapsed. However, when patients were treated with clarithromycin for 5-6 weeks, their symptoms disappeared completely and the results of their cultures and/or PCR for C. pneumoniae became negative. These data suggest that C. pneumoniae infection may cause persistent cough in adults. Furthermore, these data also indicate that it may be necessary to eradicate the organism when C. pneumoniae is detected by culture and/or PCR in patients with persistent cough.