“ The Chlamydias (24) are obligate, intracellular bacteria whose extreme
biosynthetic defects in intermediate metabolism and energy generation cause them to be
absolutely dependant on a host cell to grow and replicate. They are among the most
common of all human infectious agents and produce much disability although little
mortality.” Although they contain many complex biochemical metabolic systems, their
lack of certain essential enzymes and amino acids render them incapable of independent
existence outside a living cell.
The chlamydia are classified into three major human disease divisions:
- C. trachomatis: a) The classical eye infection, trachoma, seen primarily in
underprivileged children in developing countries, spread by fomites and flies. b)
Sexually transmitted diseases spread by direct contact among sexually active
teenagers and adults including urethritis/cervicitis, epidymitis/salpingitis, and
lymphogranuloma venereum. In this cluster are also inclusion conjunctivitis from
infected pregnant mothers and infant pneumonia. - C. psittaci: The psittacosis agent spread as an aerosol from infected birds and
causing atypical (non-bacterial) pneumonia of various degrees of morbidity and
mortality. A more recent clinical finding has been recognition of occasional cases
of blood culture-negative endocarditis (infection of heart valves). - C. pneumoniae: A recently recognized member of the group, originally labeled
the TWAR agent, that causes a febrile respiratory disease associated with sore
throat, cough and mild atypical pneumonia. Originally confused with psittacosis,
it shares less than 10 per cent homology with the other three chlamydial species.