A fluorescent probe could help physicians to pinpoint where the dangerous bacterium Staphylococcus aureus is living in a patient's body.

Some bacterial infections are difficult to locate directly, so James McNamara of the University of Iowa in Iowa City and colleagues created a molecular probe that reacts with an enzyme made by S. aureus called micrococcal nuclease. The enzyme cuts up small strings of nucleic acid molecules, and the probe consists of two nucleic acid bases attached to a fluorescent molecule.

The researchers injected the probe into a mouse with a S. aureus infection in its muscles. The bacterial enzyme cut the probe in two, activating the fluorescent molecule and causing the bacteria to glow under a microscope.

Several other pathogens produce these nuclease enzymes, suggesting that the approach could be customized to detect specific species of bacteria.

Nature Med. http://doi.org/rcf (2014)