Photodynamic therapy may offer a new way to treat chronic infection in cystic fibrosis.

Chronic bacterial lung infection is a major cause of disease and death in people with cystic fibrosis. Pseudomonas aeruginosa is a particular problem as it cannot usually be eradicated with antibiotics, which cannot penetrate the thick mucus in the lungs (above).

Researchers at Queen's University Belfast, led by Ryan Donnelly, have been exploring the potential of photodynamic antimicrobial chemotherapy (PACT) to destroy this bacterium. In PACT, a photosensitising drug is delivered to tissues and then activated by a targeted light source, to selectively destroy microbial cells. The hope is that a suitable drug could be delivered in a spray directly into the lungs.

The team examined two 'typical' photosensitisers, which have been used before in PACT to kill other kinds of bacteria. They showed that both light and the photosensitisers were able to penetrate an artificial cystic fibrosis mucus – vital for PACT to be effective.

PACT with either photosensitiser killed P. aeruginosa growing freely and in biofilms – both of which are seen in people with cystic fibrosis. Further work is now needed to test the feasibility of this therapy in animal models of the disease.

Image credit: ISM/Science Photo Library

External links

• Donnelly RF et al. Delivery of photosensitisers and light through mucus: investigations into the potential use of photodynamic therapy for treatment of Pseudomonas aeruginosa cystic fibrosis pulmonary infection. J Control Release 2007;117(2):217–26.