Detection of Chlamydia pneumoniae DNA and antigen in the circulating mononuclear cell fractions of humans and koalas
Bodetti, TJ & Timms, P 2000, Infection and Immunity, vol. 68, no. 1, pp. 2744-2747.
DNA and antigens of the common respiratory pathogen Chlamydia pneumoniae were found in the peripheral blood mononuclear cell (PBMC) fractions of 30% of koalas from a sampled population at Lone Pine Koala Sanctuary. The presence of the pathogen in these cells confirms that C. pneumoniae can use PBMCs as a pathway for disseminating and subsequently infecting non-respiratory sites. A similar phenomenon was observed in the blood of human donors, suggesting that the dissemination of C. pneumoniae to non-respiratory sites is not unique in humans but rather is an inherent characteristic of the bacterium.
C. pneumoniae commonly occurs in humans, infecting typically respiratory but also non-respiratory sites throughout the body. A potential link between the bacterium and human atherosclerosis, or cardiovascular disease, has been established; however, causation has not yet been proven. The only other natural host of C. pneumoniae is the koala, in which the same types of infections that occur in humans have been observed including respiratory disease. In koalas, C. pneumoniae has been detected at ocular, urogenital and respiratory sites. The presence of C. pneumoniae DNA and antigens in PBMCs demonstrates that the bacterium is able to spread around the body to these non-respiratory sites via the peripheral blood system by infecting circulating PBMCs. This transport mechanism is a possible factor in strengthening the link between the pathogen and atherosclerosis.
C. pneumoniae is thought to be present in nearly every wild and captive koala population. Although a link exists between this pathogen and atherosclerosis in humans, the shorter lifespans and lower-cholesterol diets of koalas compared to humans puts koalas at a much lower risk of developing heart disease. Despite being a low risk in this regard, the finding that the bacterium can spread throughout the body of a koala via the peripheral blood system to infect non-respiratory sites is significant for the management of infection in both wild and captive populations.
Summarised by Joanna Horsfall
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