The bacterium Pseudomonas aeruginosa needs iron to establish and maintain a biofilm in the lungs of cystic fibrosis patients, and therapies have been proposed to deprive the bacteria of this necessary element. However, these techniques may not work, according to a new study published in mBio, the online open-access journal of the American Society for Microbiology, because they only target one of the two types of iron that are available in the lung.
Current therapies focus on removing ferric iron [Fe(III)] but leave plenty of ferrous iron [Fe(II)] behind for the bacteria to use, according to the study. The concentration of Fe(II) present in the lungs of patients with cystic fibrosis correlates with disease severity, a sign that pathogens not only use ferrous iron - they thrive on it. These findings could have implications for treatment of P. aeruginosa in patients with cystic fibrosis.
"It is clear that the percentage of the total iron pool that is Fe(II) is substantial, particularly in severely ill patients," write the authors. Despite a wealth of data on the abundance of iron in the airways of patients with cystic fibrosis, this study is the first to make direct measurements of two different bioavailable forms of iron, Fe(III) and Fe(II).
An optimal concentration of bioavailable iron is needed to establish the formation of P. aeruginosa biofilms, thick accumulations of bacteria, polysaccharides, and cellular debris that can build up in the lungs of cystic fibrosis patients. It's also integral to stabilizing biofilms, so therapies have been proposed to perturb P. aeruginosa's uptake and acquisition of iron to fight biofilm development in the lung.
Because Fe(III) is commonly assumed to be the dominant physiologically-relevant form of iron, therapies focus on blocking Fe(III) acquisition. However, Fe(II) may also be present in the lung, reasoned the authors, a fact that could undermine iro
|Contact: Jim Sliwa|
American Society for Microbiology