< > Home : FAQ : Professional : Chlamydiales : Immunobiology : Infections : Diagnosis & Treatment : Links : Contact Us

C. pneumoniae was initially isolated in 1965 from a child’s conjunctiva during a trachoma vaccine trial in Taiwan [Grayston, 1965]. This particular isolate was called TW-183 [i.e. Taiwan isolate number 183]. Although isolated from an ocular site, TW-183 was recognised not to be C. trachomatis because its inclusions in cells did not stain with iodine and it failed to cause follicular conjunctivitis in monkeys or to kill mice on intravenous inoculation. TW-183 and another similar strain [IOL-207,  isolated in Iran from an ocular site by John Treharne and colleagues from the Institute of Ophthalmology, London; Dwyer et al., 1972] could not at that time be differentiated from C. psittaci on phenotype alone, although it showed some serological differences. These strains were therefore considered to be 'atypical isolates'. Nowadays DNA and antigenic criteria are used to differentiate C. pneumoniae from other species in the Chlamydiaceae and its entire genome was sequenced in 1998 [Kalman et al., 1999].

It was soon realised that TW-183 and similar "atypical" isolates were a cause of respiratory rather than ocular infections. With respect to the respiratory tract, the organism was first isolated in 1983 from the pharynx of a University of Washington student with pharyngitis. This isolate was labelled AR-39 [acute respiratory isolate 39].  However, when it was recognised that it was the same kind of atypical isolate as TW-183, these organisms became known as TWAR isolates. In a seminal study published in 1986, 13 of 386 students presenting with acute respiratory infections were found to have serological evidence of infection by TWAR and the organism was isolated from 8 students [Grayston et al., 1986]. TWAR was formally recognised as a new chlamydial species in 1989 and was renamed Chlamydia pneumoniae [Grayston et al., 1989]. However, in the new chlamydial taxonomy, the former C. pneumoniae and C. psittaci have been reassigned to the new genus Chlamydophila [meaning: like / similar to Chlamydia]. Thus the name Chlamydia pneumoniae is now obsolete. Numerous studies have confirmed that C. pneumoniae is indeed an important respiratory pathogen. However, it is the association of C. pneumoniae with a number of chronic human diseases, including coronary heart disease, which has excited the most interest. Table 1 summarizes the rather disparate epidemiology of the chronic human diseases with which C. pneumoniae has been associated. In the following section, the strength of evidence for C. pneumoniae as an important cause of chronic disease is examined.

Table 1. Epidemiology of diseases associated with Chlamydophila pneumoniae.

[MEW & YW] March 2002

References

Dwyer, R. S. C., Treharne, J. D., Jones, B. R. & Herring, J. (1972). Results of micro-immunofluorescence tests for detection of type-specific antibody in certain chlamydial infections. British Journal of Venereal Diseases 48, 452 - 459.

Grayston, J. T. (1965). Immunisation against trachoma. Pan American Health Organization Scientific Publication 147, 549.

Grayston, J. T., Kuo, C. C., Wang, S. P. & Altman, J. (1986). A new Chlamydia psittaci strain, TWAR, isolated in acute respiratory tract infections. New England Journal of Medicine 315, 161 - 168.

Grayston, J T., Kuo, C. C., Campbell, L. A. & Wang, S. P. (1989). Chlamydia pneumoniae sp-nov for Chlamydia sp strain TWAR. International Journal of Systematic Bacteriology 39, 88 - 90.

Kalman, S., Mitchell, W., Marathe, R., Lammel, C., Fan, J. & Hyman, R. W. et al. (1999). Comparative genomes of Chlamydia pneumoniae and C. trachomatis. Nature Genetics 21, 385 - 389.