In Vitro Evaluation of Photoactivated Rose Bengal for Growth Inhibition of Fungi Isolated From Keratitis

The aim of this study was to evaluate the activity of photoactivated 0.1% rose bengal (RB) for in vitro growth inhibition of the most prevalent fungi isolates in infectious keratitis.

Eight corneal clinical isolates were included in the experiments: Fusarium solani complex, Purpureocillium lilacinum , Candida albicans , Candida parapsilosis complex, Exophiala oligosperma , Scedosporium apiospermum complex, Aspergillus niger complex, and Curvularia geniculata . Microorganisms, previously identified by phenotypical methods, were grown and incubated at specific conditions and prepared in suspension for concentration adjustments. The following groups were evaluated in triplicate: group I, no treatment; group II, treated with RB and exposed to the dark for 30 minutes; group III, exposed to green-light light-emitting diode 7.2 mW for 30 minutes (photodynamic therapy [PDT]); and group IV, treated with RB and PDT (RB-PDT). The final work concentration was 10 4 cells per mL. The RB-PDT was combined with Amphotericin B (AmphoB) to target isolates that were not inhibited by RB-PDT alone. Plates were incubated at specific conditions and photographed after growth for pixel analyses.

The growth was inhibited after RB-PDT for F. solani complex, P. lilacinum , C. albicans , C. parapsilosis complex, and E. oligosperma , and not inhibited for S. apiospermum complex, A. niger complex, and C. geniculata , even though combining RB-PDT with AmphoB.

RB-PDT presented good activity against five of the tested microorganisms. For the first time, we demonstrated that RB-PDT could inhibit growth of P. lilacinum , C. parapsilosis complex, E. oligosperma , and not inhibit S. apiospermum , A. niger complex, and C. geniculata , even when combined with AmphoB.