SET your phages to stun. Researchers have devised a way to engineer a class of bacteria-destroying viruses to make them more clinically useful. The phage viruses could eventually be used to kill disease-causing bacteria in the body while leaving our “good” bacteria unharmed.

Many phage viruses infect and replicate inside bacteria, killing them. This makes phages a possible alternative to antibiotics as resistance to these drugs grows. What’s more, most phages infect only one species or even a few strains within a species; antibiotics aren’t so selective.

But that specificity is a problem: it might not be clear which pathogenic bacterial strain is present in an infection, so a cocktail of several phages might be needed to guarantee effective treatment. Each may have to pass regulatory approval separately.

Timothy Lu and his colleagues at the Massachusetts Institute of Technology aim to get round this by making a single phage modifiable with bacteria-attacking machinery from other phages. In theory, that could reduce regulatory hold-ups.


Phage DNA is difficult to manipulate in the lab, so Lu’s team made their modifications while the phages were in yeast. They swapped in genes from other phages to change the phage tail – a needle that punches through a target bacterial membrane. They could then direct the virus to target new bacteria.

“We built a phage design system that is a lot more efficient than anything that came before,” says team member Sebastien Lemire.

The phage normally kills E. coli, but by swapping in different tails, the team made it kill at least 99 per cent of either Yersinia or Klebsiella bacteria (Cell Systems, doi.org/74j).

“It may well make it possible to get new therapeutic phages much more quickly,” says Elizabeth Kutter at Evergreen State College in Olympia, Washington.

This article appeared in print under the headline “Targeted drugs could kill only harmful bugs”