Chlamydia pneumoniae Prospects and Predictions for an Emerging Pathogen


Chlamydial diseases have long been recognized as a significant cause of morbidity in humans. Although acute disease is rarely fatal, chronic infections with their associated sequelae have an enormous impact both on the economy and on the quality of life of those who suffer from these conditions. For Chlamydia trachomatis, acute infections include conjunctivitis and the sexually transmitted diseases; chronic infections can lead to trachoma, tubal factor infertility, pelvic inflammatory disease, and reactive arthritis.(1) The identification and speciation of Chlamydia pneumoniae about 15 years ago and the recognition that a large percentage of the world's population has been exposed to this organism(2) have led many investigators to inquire into certain diseases with unknown etiology, some of which were not thought to have an infectious component. For Chlamydia pneumoniae, acute infections are localized to the airways, with pneumonia and bronchitis being the most common disease conditions.® Chronic sequelae, developing from acute or asymptomatic infections, cannot be definitively attributed to C. pneumoniae at this time, although evidence is accumulating to suggest that C. pneumoniae infection may also lead to debilitating (asthma) and even fatal (heart disease) conditions. Table I shows acute diseases caused by C. pneumoniae and the chronic diseases with which it has been associated. Possible pathological associations are also listed.

C. pneumoniae, like other members of the genus, has the characteristic biphasic life cycle between the infectious, metabolically inert elementary body (EB) and the noninfectious, metabolically active reticulate body (RB). EBs are

SCOT P. OUELLETTE and GERALD I. BYRNE • Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, Tennessee.

C. pneumoniae Diseases and Putative Chronic Sequelae

Acute disease

Chronic disease

Possible ch lamydia-associated pathology



Community-acquired pneumonia


Macrophage/en dothelial dysfunction, chronic inflammatory response, LDL oxidation

Serology, IHC, PCR, EM, culture

4,5, 6, 7 (see 8 for review)

Bronchitis Pharyngitis


Ciliary dysfunction, inflammatory and IgE responses, bronchial hyperrespo nsi veness

Serology, PCR, MtF, culture, treatment

9,10 (see 11 for review)

Other respiratory tract diseases

Reactive arthritis

Chronic inflammatory response, HLA type association


12, 13



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