Iron Plays Important Role in Formation of Drug-Resistant Bacteria

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Iron and Bacterial Infections

Understanding the role iron plays in the formation of bacterial infections could shed more light on drug-resistant strains and give doctors new hope of improving the health of patients suffering from cystic fibrosis and other debilitating diseases, according to a recent report in a leading scientific journal.

Researchers from the University of Colorado at Denver and Health Sciences Center and the University of Washington-Seattle made an important connection between disease-causing bacteria and their ability to use certain forms of iron to form complex communities that are highly resistant to antimicrobial drugs. The communities, called biofilms, also resist the body's defenses against infections.

"There is a very delicate and integrate balance between the host and the infectious agent with regard to the availability of iron," said Michael Vasil, PhD, professor of microbiology at UCDHSC and co-author of the study. "If the organism is able to out-compete the host for available iron or destroy its ability to withhold iron, then it is much more likely to cause a serious infection."

The findings of the study, published in the July 18-22 edition of Proceedings of the National Academy of Sciences of the United States, could result in better antibiotics and increased awareness of how iron in the diet might affect people battling certain illnesses.

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In particular, researchers are hopeful their findings will lead to new treatments for people living with cystic fibrosis, a genetic disease that causes the body to produce abnormally thick mucus that clogs the lungs and leads to life-threatening infections. The thick substance contains biofilms produced by the most prevalent bacterial infectious agent in patients with cystic fibrosis, Pseudomonas aeruginosa, Vasil said.

About 30,000 Americans are living with cystic fibrosis, and another 10 million are unknowing carriers, according to the Cystic Fibrosis Foundation.

According to the study, predatory, iron-loving infectious agents such as Pseudomonas aeruginosa require certain kinds of iron to be able to form biofilms. During an infection, bacteria obtain this iron by effectively overcoming the host's ability to withhold it.

In most healthy people, the body can keep iron away from an infectious agent by producing proteins such as lactoferrin and storing excess iron in certain organs such as the liver. However, Pseudomonas aeruginosa and similar bacteria are better at producing strong iron-binding compounds called siderophores, or iron lovers, and are more likely to infect a susceptible host by interfering with the function of proteins such as lactoferrin. These bacteria can steal iron from the host by either making siderophores that bind iron more effectively than the host's proteins or by actually degrading the host's iron-binding proteins and using the released iron to make biofilms.

The University of Colorado at Denver and Health Sciences Center is one of three campuses in the University of Colorado system.

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