Effect of rose bengal photodynamic therapy on Staphylococcus aureus and Candida spp cultures

  • Baanu Paul Remician

Western Sydney University thesis: Master's thesis

Abstract

The increase in antimicrobial resistance worldwide is of great concern. Staphylococcus aureus (SA) and Candida are two of many microorganisms which are currently leading causes of nosocomial infections, hence the need to identify an alternate treatment method for resistant microbes is vital. Photodynamic Therapy (PDT), with Rose Bengal (RB) as a sensitising agent, has been suggested as a feasible treatment to inhibit the growth of these organisms. This study expands on a protocol developed in a previous study, which demonstrated the phototoxic effects of PDT towards isolates of S. aureus, (SA19 and SA70), different species of Candida (C.albicans, C.glabrata, C.kruseii and C. parapsilosis) and Pseudomonas aeruginosa, which were grown on nutrient rich agar plates in darkness. Different green LED light sources were applied to samples containing microbial cells and RB for 5,10 and 15 minutes. The cells were then incubated for 48 hours before CFU/mL counts were performed to identify percentage of viable cells. This showed that Rose Bengal Photodynamic Therapy (RB-PDT) effectively inhibited the growth of S.aureus and Candida spp. The optimal protocol for inhibition of S.aureus and Candida was 25 µg/mL for 10 minutes and 37.5 µg/mL for 15 minutes respectively. Additionally, the use of different light sources showed the intensity of light is important for the effectiveness of PDT. The commercial LED torches were found to be as effective as a custom-built green LED light source developed for a previous study. RB-PDT with commercially available light sources may provide a cost-effective and useful alternative treatment of superficial microbial infections.
Date of Award2022
Original languageEnglish

Keywords

  • rose bengal
  • photochemotherapy
  • Staphylococcus aureus
  • Candida

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