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't 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's ability to break up biofilms by arming it with the gene for a slime-busting enzyme.

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 ...