ANTI-FOULING agents produced by marine algae could help prevent some of the most troublesome hospital infections. The chemicals don鈥檛 kill bacteria but instead stop them ganging together to form dense colonies that resist all treatment.
Up to a fifth of all implanted devices, from catheters to heart valves and hip joints, become infected. Such infections can be life-threatening, and also mean that patients may have to face major surgery again.
Part of the problem is that bacteria that usually live harmlessly on the skin attach themselves to the implants, forming thick colonies called biofilms that are impervious to the patient鈥檚 immune system and antibiotics alike. But coating catheters with chemicals called furanones can stop the biofilms forming in the first place, Jasjit Baveja of the Cooperative Research Centre for Eye Research and Technology in Sydney told a meeting in the city last week.
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Furanones were identified a few years ago as the agents that keep the red alga Delisea pulchra free of bacteria and other marine organisms. Now Baveja and her colleagues have found that furanones reduced the numbers of a bacterium called Staphylococcus epidermidis coating plastic plates by 90 per cent in the lab. The bacteria also produced 95 per cent less of the slime that forms part of a biofilm. Furanones also inhibit the growth of other bugs such as S. aureus, which grows on metal implants and is often resistant to antibiotics.
When the researchers tested the furanone-coated catheters in sheep, they found they hosted 85 per cent fewer bacteria of all types after 12 weeks. 鈥淭he uncoated catheters were covered with pus,鈥� says Baveja.
The furanones don鈥檛 kill the bacteria. Rather, they appear to stop the bugs forming a biofilm, perhaps by preventing them from turning on the genes that allow them to stick on to a surface and to each other.
The fact that furanones don鈥檛 kill the bugs is an advantage, not only because dead bacteria can release harmful toxins, but also because bacteria should be less likely to develop resistance to the chemicals. Other groups are developing antibiotic-coated implants, but there are fears that this will encourage resistant strains to emerge (快猫短视频, 13 November 1999, p 7).
The next step will be to prove that furanones are safe to use in humans. Baveja hopes that tests of coated implants in people will begin within five years.
In a separate study, it was found that lactoferrin, an iron-gobbling protein found in human tears, stops the bacterium Pseudomonas aeruginosa forming biofilms (Nature, vol 47, p 552). Besides fouling implants, P.aeruginosa films are usually what kills people with cystic fibrosis.