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A study of human respiratory tract chlamydial infections in Cambridgeshire 1986-88
T G Wreghitt1, C E Barker, J D Treharne
1Clinical Microbiology and Public Health Laboratory, Addenbrooke's Hospital, Cambridge.
Abstract:
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.
Insights
Chlamydia psittaci infections are more common in human respiratory illness in Cambridgeshire than Chlamydia pneumoniae (TWAR). C. psittaci infections are often linked to bird contact, unlike C. pneumoniae.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Respiratory Medicine
Background:
- Human respiratory tract chlamydial infections have been historically challenging to differentiate.
- Distinguishing between Chlamydia psittaci and Chlamydia pneumoniae (TWAR) infections was previously difficult.
Purpose of the Study:
- To differentiate between C. psittaci and C. pneumoniae infections in Cambridgeshire.
- To determine the relative incidence of these two chlamydial infections.
- To investigate potential sources of infection, such as bird contact.
Main Methods:
- Utilized the micro-immunofluorescence (micro-IF) test for serological diagnosis.
- Analyzed serum samples from 50 patients with community-acquired respiratory symptoms and high Chlamydia complement fixation test titres (≥64).
Main Results:
- Twenty-five patients (50%) showed evidence of recent C. psittaci or C. pneumoniae infection.
- C. psittaci infection was identified in 19 patients (76% of positive cases), with 16 reporting recent bird contact.
- C. pneumoniae infection was found in 6 patients (24% of positive cases), with only 2 reporting recent bird contact.
- C. psittaci was isolated from birds associated with human infections, but C. pneumoniae was not cultured from birds linked to human cases.
Conclusions:
- C. psittaci is a more frequent cause of diagnosed chlamydial respiratory infections in this Cambridgeshire cohort compared to C. pneumoniae.
- Bird contact is strongly associated with C. psittaci respiratory infections.
- The micro-IF test is effective for differentiating these chlamydial infections.