Microbial ‘vampires’ killed by light

Vanderbilt University researchers have discovered a way to destroy Staphylococcus aureus (staph) using light in combination with an enzyme-activating small molecule. The research was published this summer in the Proceedings of the National Academy of Sciences (PNAS).

Staphylococcus aureus (staph) is the leading cause of hospital-acquired infections. Though about 30% of healthy people carry the bacteria in their noses, staph can also cause serious infections such as sepsis and pneumonia. Some strains of the bacteria, such as MRSA, are antibiotic-resistant and can be deadly.

In the new study, the researchers used an enzyme-activating small molecule they developed called ‘882. This molecule is one of about a dozen synthetic small molecules known to activate, rather than inhibit, an enzyme. It activates a bacterial enzyme called CgoX, which in turn causes accumulation of a photoreactive molecule named CPIII. When the researchers hit the CPIII with light of a certain wavelength, the molecule produced reactive oxygen species that killed the S. aureus bacteria. This was accomplished in mouse models of skin and soft tissue infections.

A treatment that uses a drug in combination with a certain type of light is called photodynamic therapy (PDT). PDT is used to treat skin conditions such as acne, as well as certain cancers. For example, according to the NCI, the FDA has approved a photosensitizing agent for use in PDT to treat both esophageal and non-small cell lung cancer. However, PDT hasn’t typically been used to treat infections because the process typically ends up killing human cells. In contrast, the ‘882 molecule selectively targets a bacterial enzyme, allowing for the destruction of S. aureus bacteria without harming human cells.

The research team likened S. aureus to microbial vampires, because staph bacteria require human blood to grow, in particular the iron from our hemoglobin. Then, like sunlight strips vampires of their powers, light and photodynamic therapy can stop bacteria. As senior author Eric Skaar, PhD, MPH, said in a tweet: “If S. aureus is going to drink our blood like a vampire, let’s kill it with sunlight.”

Do you work in this area of science? Check out our available bacteriology reagents to see if any could help accelerate your research. You also might be interested in past blog posts covering antibiotic research: