Effect of vacuum and thermal shock on laser treatment of Trichophyton rubrum (toenail fungus)

Abstract

The eradication of Trichophyton rubrum has been attempted via laser irradiation because it could result advantageous relative to current clinical therapies. Anticipating that the necessary thermal effects could unintentionally damage the underlying toe dermal layer, we have explored two auxiliary approaches: (a) laser irradiation under vacuum pressure, with and without water dousing and, (b) cooling followed by laser heating (thermal shock). The rationale is that at low pressures, the temperature necessary to achieve water evaporation/boiling is significantly reduced, thus requiring lower fluences. Similarly, a thermal shock induced by cooling followed by laser irradiation may require lower fluences to achieve fungus necrosis. For all experiments presented we use a Cooltouch, model CT3 plus, 1320 nm laser to irradiate fungi colonies. The vacuum pressure experiments exposed fungi colonies to a subatmospheric pressure of 84.7 kPa (25 inHg) with and without water dousing for 5 min, followed by irradiation with 4.0 J/cm 2 fluence and 40-90 J total energies. The thermal shock experiments consisted of three sections at 4.8 J/cm 2 : cooling the fungus to 0 o C at 0.39 o C/min and then irradiating to 45-60 o C; cooling to -20 o C at 1.075 o C/min and irradiating to 45 o C; and cooling to -20 o C at 21.5 o C/min and irradiating to 45 o C. Fungus growth rate over a 1-week period assessed the feasibility of these procedures. Results indicated both approaches hamper the growth rate of fungi colonies relative to untreated control samples, especially water dousing under vacuum conditions and slow cooling rate preceding irradiation for thermal shock effect.

Controlled inactivation of Trichophyton rubrum using shaped electrical pulse bursts: Parametric analysis

“…According to the World Health Organization (WHO) the dermatophytes, which are a common short label for the thee genera of fungi— Epidermophyton , Trichophyton , and Microsporum , are responsible for the cutaneous mycoses and affect about 25% of the world's population . They are unable to grow in the living tissues, but instead they are the filamentous keratinophilic fungi, where the Trichophyton rubrum is the most frequent in clinical cases of tinea unguium , tinea corporis , tinea pedis , and tinea cruris . According to the recent epidemiologic findings, in the 115,846 cases over 37 years (Korea) the increasing prevalence of T. rubrum (88.35%) compared to other dermatophytes was observed .…”

“…1 They are unable to grow in the living tissues, but instead they are the filamentous keratinophilic fungi, where the Trichophyton rubrum is the most frequent in clinical cases of tinea unguium, tinea corporis, tinea pedis, and tinea cruris. [1][2][3] According to the recent epidemiologic findings, in the 115,846 cases over 37 years (Korea) the increasing prevalence of T. rubrum (88.35%) compared to other dermatophytes was observed. 4 This fungus is attributed to main causative agents of tinea pedis and onychomycosis in Lithuania.…”