Researchers announced this week the discovery of a mechanism by which Mycobacterium avium - a bacterium which can result in serious lung infections and is prevalent in emphysema and AIDS patients among others - infects tissue cells or macrophages and thus compromises the body's immunity.
Results of the study, led by researchers at Oregon State University, will be published in the Proceedings of the National Academy of Sciences. Other co-authors were from the University of Nebraska.
The key to the bacterium's ability to enter environmental amoebas , and ultimately humans , is an island of genetic material acquired through evolution from another bacterium, according to Luiz E. Bermudez, a professor of biomedical sciences in OSU's College of Veterinary Medicine and an author of the study.
"Without these acquired genes, the bacterium is very inefficient in infecting environmental amoeba, which is the environmental host," Bermudez said. "In fact, its efficiency is close to zero. But with this island of acquired genetic material, the bacterium finds a way to get inside the cells and it takes control, not the phagocyte."
Phagocytes are cells that engulf and digest pathogens and cellular debris, and in humans serve as the body's initial immune response.
The researchers did not find a similar island of acquired genetic material in two similar bacteria, Mycobacterium tuberculosis and Mycobacterium paratuberculosis, which causes Johne's disease.
M. avium exists in the environment and is thought to infect humans when the infected environmental hosts , amoebas , are inhaled or swallowed.