A VIRUS has been genetically engineered that could help to break down the slimy colonies of bacteria that clog medical devices such as catheters.
Biofilms, which contain bacteria such as Staphylococcus aureus, can form on medical devices, where they clog fine tubes and make the bacteria hard to eradicate. Even if the bugs don鈥檛 carry genes for drug resistance, the slimy matrix often helps to protect them from antibiotics.
Some researchers are already trying to battle biofilms by deploying viruses known as phages that infect and kill the unwanted bacteria. Now Tim Lu and Jim Collins of Boston University have gone a step further. They have boosted one phage鈥檚 ability to break up biofilms by arming it with the gene for a slime-busting enzyme.
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鈥淭hey have armed phages with the gene for a slime-busting enzyme鈥�
After infiltrating a bacterial cell, the engineered phages hijack its internal machinery and manufacture large quantities of a slime-munching enzyme. They then burst the cell open and release the enzyme, which breaks down the biofilm by digesting a complex carbohydrate that helps hold it together. When the pair applied the enzyme-producing phages to Escherichia coli biofilms the phages easily outperformed their non-engineered cousins, removing about 100 times as many bacterial cells over 24 hours ().
Although Lu and Collins have so far engineered just one phage, T7, which targets E. coli, it should be possible to engineer phages that infect different bacterial species and produce enzymes to target a variety of biofilm components. 鈥淭here鈥檚 no limit to that,鈥� says Collins. Naturally occurring biofilms tend to house a range of species, so this versatility will be important.
Because there is a risk that phages will provoke an immune reaction, there will need to be safety testing before they are used to bust biofilms that form on devices that are implanted deep in the body. So they will probably find their first use as an addition to a fluid for flushing out catheters, which are accessible from outside the body: they can become blocked as they rest inside a patient鈥檚 veins or bladder.
Still, the bacterial colonies are so persistent that it may be necessary to combine the engineered phages with other methods, including conventional antibiotics. 鈥淏iofilms are tough,鈥� says Phil Stewart, who heads the Center for Biofilm Engineering at Montana State University in Bozeman. 鈥淭here鈥檚 not going to be a silver bullet that knocks everything out.鈥�
