A study of human respiratory tract chlamydial infections in Cambridgeshire 1986-88.

Human respiratory tract chlamydial infections have been studied in Cambridgeshire for many years, but until recently we have been unable to distinguish between infection with Chlamydia psittaci or Chlamydia pneumoniae (TWAR). In this study, we have employed the micro-immunofluorescence (micro-IF) test for this purpose and to look for the relative incidence of C. psittaci and C. pneumoniae infections in Cambridgeshire. Among 50 patients with community-acquired respiratory tract symptoms whose serum samples had Chlamydia complement fixation test titres greater than or equal to 64, 25 had evidence of recent C. psittaci or C. pneumoniae infection. Nineteen (76%) of the 25 patients had evidence of recent C. psittaci infection and of these 16 (84%) had recently had contact with birds. Six patients (24%) had evidence of recent C. pneumoniae infection, and of these, only two (33%) had recently had contact with birds. While C. psittaci was grown from several of the birds associated with human C. psittaci infection, it was not cultured from any of the birds in contact with the two human C. pneumoniae cases.