A component of bodily secretions, including mucus and tears, stops bacteria forming potentially deadly biofilms. These slime-encased colonies frequently clog up medical implants and the lungs of patients with cystic fibrosis. They are highly resistant to antibiotics.
鈥淏iofilm infections are a major medical problem,鈥� says Pradeep Singh of the University of Iowa, who led the new work. 鈥淏ut though the human body is constantly exposed to disease-causing bacteria, biofilms do not normally form unless a person鈥檚 defences have been compromised by disease. This suggested to us that the body might have a natural anti-biofilm defence mechanism.鈥�
The team focused on a protein called lactoferrin, a component of the body鈥檚 antibacterial defence system. They studied its effect on the bacterium Pseudomonas aeruginosa, in conditions ideal for biofilm formation.
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Even small amounts of lactoferrin stopped biofilms forming, the team found. The protein did not kill the bacteria or slow its growth 鈥� but it successfully kept individual bacteria on the move, preventing them aggregating into groups. The bacteria then remained exposed and vulnerable to antibiotics.
Iron trap
Lactoferrin achieves its effect by trapping iron, a crucial bacterial nutrient. When iron levels are low, bacteria roam across a surface in search of more. Other compounds that trap iron have been developed to improve deodorants.
鈥淟actoferrin is present in lung secretions, tears, saliva, breast milk and other bodily fluids that come in contact with bacteria,鈥� says Singh. 鈥淓verywhere this defence is needed, lactoferrin is present in large quantities.鈥�
However, the team also found that lactoferrin did not break down existing biofilms. 鈥淭his means it would have to be used early in infections, before biofilms form,鈥� says Singh.
Singh hopes medical devices, such as catheters, could be coated in lactoferrin, or another iron-trapping drug. 鈥淭his might prevent the formation of biofilms on these surfaces by limiting local iron concentrations,鈥� he says.
Other groups are working on alternative approaches to tackling biofilms. A team in Australia recently successfully coated catheters with furanones 鈥� chemicals produced by marine algae to protect themselves from bacterial attack. 鈥淏ecause of the difficulty of this problem, multiple approaches will probably be needed to develop effective anti-biofilm therapies,鈥� Singh says.
Journal reference: Nature (vol 417, p 552)