Light Integrated Gel Healthcare Technology

Antibiotic resistant bacteria are a therapeutic challenge to which new solutions must be found. Staphylococcus aureus is a human pathogen that causes local and systemic infections which can be life-threatening. Methicillin-resistant S. aureus (MRSA) is well known as a source of nosocomial infection and such strains often have broad spectrum resistance to many antibiotics. Recalcitrance to antibiotic therapy in S. aureus is also associated with a certain sub-population of cells known as small-colony variants (SCVs). SCVs are known to reside intra-cellularly in a quiescent state where they evade host defences and antimicrobial therapy, and can be a reservoir for recurrent infection.
Lethal photosensitisation is a mechanism whereby bacterial cells are killed by reactive molecules (e.g. singlet oxygen and other free radicles) produced by a photosensitive dye when activated by light of an appropriate wavelength and intensity.

Killing antibiotic resistant bacteria using a dye combined with a red light.

We report that genetically created S. aureus SCV, parent strains, and an MRSA strain were susceptible to lethal photosensitisation using the photo-sensitive dye, toluidine blue (TBO), with kills of up to 6 logs observed. We show effective delivery and activation of TBO in solution and when loaded into a hydrogel.