The Susceptibility of Dermatophytes to Photodynamic Treatment with Special Focus on Trichophyton rubrum

Abstract

Owing to the accessibility of skin to light, many applications of photodynamic treatment (PDT) have been developed within dermatology. The recent increase of dermatological antimicrobial PDT investigations is related to the growing problem of bacterial and fungal resistance to antibiotics. This review focuses on the susceptibility of dermatophytic fungi, in particular Trichophyton rubrum, to PDT and shows its potential usefulness in treatment of clinical dermatophytoses. There are no data indicating significant differences in PDT susceptibility between various dermatophytes and it is unlikely that treatment problems of especially T. rubrum with current antimycotics would occur in case of PDT. Red light 5-aminolevulinic acid-mediated PDT is after repeated sessions successful in in vivo treatment of onychomycosis (fungal nail infection) caused by various dermatophytes. Regarding skin dermatophytoses, UVA-1 PDT with cationic porphyrins appears to be safe and efficient. Most effective toward T. rubrum ex vivo is 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) when combined with UVA-1 radiation or red light; this creates the possibility of efficiently treating nail infections and remaining spores in hair follicles. If the promising in vitro and ex vivo results could be transferred to clinical practice, then PDT has a good prospect to become a worthy alternative to established antifungal drugs.

The Tetrazole VT-1161 Is a Potent Inhibitor of Trichophyton rubrum through Its Inhibition of T. rubrum CYP51

“…These antimycotic agents are most effective against the growing organism but are often ineffective against static phases of the organism, such as T. rubrum conidia, leading to reinfection, unless prolonged treatment regimens are adopted. Recently, photodynamic treatments have been developed using photosensitizers in combination with UV-A1 radiation (340 to 400 nm) to kill both the mycelial form and the conidia of T. rubrum (13) in topical dermal infections. The antifungal agents most commonly used against T. rubrum are ketoconazole, fluconazole, terbinafine, and flucytosine (13).…”

In Vitro Photodynamic Inactivation of Plant-Pathogenic Fungi Colletotrichum acutatum and Colletotrichum gloeosporioides with Novel Phenothiazinium Photosensitizers

“…One of the factors that may explain the lack of damage is that the PS did not cross the leaf cuticle. As the reactive species generated during PDT have very short half-lives, their diffusion is limited, and therefore, damage is restricted to structures close to the PS (18). As the PS remained outside the cuticle, which is approximately 4 m thick, the internal leaf structure was not damaged by the PDT.…”

“…APDT has been used to treat human mycoses caused mainly by fungi of the genera Candida and Trichophyton (15,16,18,29,30). It is thus logical that novel applications of APDT are explored, including its use to control plant pathogens.…”

“…Antimicrobial photodynamic treatment (APDT) is an alternative and promising antifungal discovery platform that can be used to control localized mycoses in animal hosts or to kill fungi in the environment (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). The approach is based on the use of a photosensitizer (PS) that binds to the surface or preferentially accumulates in the target fungal cell (13,14,17,20).…”

Blue Dye and Red Light, a Dynamic Combination for Prophylaxis and Treatment of Cutaneous Candida albicans Infections in Mice

“…Numerous published studies have shown PDT to be highly effective in the in vitro inactivation of fungi (19,20,31). In addition, it is considered that the development of resistance to PDT by microbes is an unlikely event, because PDT is typically a multitarget process, which is a difference between PDT and most other antifungal drugs (22).…”