The effects of heat on Sporothrix schenckii in vitro and in vivo

Hyperthermia is a promising potential adjunct to treating sporotrichosis: A refractory case of HIV sporotrichosis and in vitro experiments on Sporothrix spp

BACKGROUND

Hyperthermia is a common monotherapy for sporotrichosis, but only in patients with special conditions, such as pregnancy and nursing. However, hyperthermia has not been used more widely for sporotrichosis in clinical practice.

PATIENTS/METHODS

An HIV-positive adult male with lymphocutaneous sporotrichosis caused by Sporothrix globosa that did not respond to conventional itraconazole therapy lasting >2 months received adjunctive therapy with local hyperthermia. To simulate the effects of heat exposure on the growth and morphology of Sporothrix spp. in vitro, S. globosa, S. schenckii and S. brasiliensis were exposed to intermittent heat (42°C) for 1 h a day for 7 or 28 days and observed under transmission electron microscopy.

RESULTS

Itraconazole combined with local hyperthermia significantly improved the lesions, and the patient was successfully cured of sporotrichosis, with no recurrence after 2 years of follow-up. Cultures of Sporothrix spp. treated with 7 days of daily heat exposure in vitro showed obvious decreases in colony diameters, but not numbers, compared with untreated cultures (p < .001). After 28 days of heat exposure in vitro, Sporothrix spp. were unable to thrive (p < .001), and ultrastructural alterations, including loose cell wall structure, incomplete cell membrane, disrupted vacuoles and fragmented nuclei, were noticeable.

CONCLUSIONS

Our case findings and in vitro experiments on Sporothrix spp., together with a literature review of previous sporotrichosis cases, suggest that hyperthermia has a clinical role as a treatment adjunct. Large-scale clinical trials are required to examine the utility of hyperthermia in various forms of cutaneous sporotrichosis.

Thermotherapy in dermatology

Heat has been used as a medicinal and healing modality throughout human history. Today, thermotherapy is being studied in the treatment of many diseases. Although the exact anti-infective mechanism of thermotherapy is yet to be solved, this historically important healing method has shown significant results in the treatments of a variety of dermatological infectious diseases ranging from simple acne to bacterial, parasitic and viral infections, in modern medicine. Induction of cellular apoptosis in medium doses and necrosis in high doses has made thermotherapy an important modality in the treatment of malignant tumors. Especially in dermatology, significant results have been achieved in the treatment of Bowen's disease, melanoma and simple warts. Thermotherapy, which today has also shown advancements in cosmetology, can be delivered by liquid nitrogen in the form of hypothermia and a variety of ways ranging from hot water pads to ultrasound and even to lasers, in the form of hyperthermia. In this article, the place of this historically important treatment method in modern medicine, especially in dermatology, has been reviewed by an extensive search of the literature.

Thermotherapy in dermatologic infections

The use of local induced hyperthermia or thermotherapy for dermatologic infections has not been fully explored in the more recent medical literature. Herein, we discuss the rationale behind the use of thermotherapy and review reported clinical experience with its use in the management of cutaneous infections.

Sporotrichosis in childhood: clinical and therapeutic experience in 25 patients

Sporotrichosis in an uncommon mycoses in childhood and is generally associated with injuries received as a consequence of farm work. We undertook a retrospective study of sporotrichosis in children and adolescents seen over a 10-year period, focusing on their clinical, epidemiologic, and mycologic features as well as treatment. We included 25 children with a mean age of 9.3 years. Most of those affected were schoolchildren (84%) from rural areas. The main clinical variety of sporotrichosis seen was the lymphocutaneous form (64%), followed by the fixed cutaneous form (36%), and one instance of the disseminated cutaneous form. Most lesions were located on the upper limbs (40%) and the face (36%). Sporothrix schenckii was isolated in all patients and 24 of 25 had a positive sporotrichin skin test. Nineteen patients were treated and cured clinically and mycologically with potassium iodide, three were cured with itraconazole and one with heat therapy.

Combined Effect of Heat, Essential Oils and Salt on the Fungicidal Activity against Trichophyton mentagrophytes in Foot Bath

This work was originally undertaken to determine the effective conditions of essential oils against Trichophyton mentagrophytes in vitro for the treatment of tinea pedis in a foot bath. Agar blocks implanted with T. mentagrophytes were immersed in 0.1% aqueous agar containing two-fold dilutions of essential oils with or without sodium chloride at 27 degrees C, 37 degrees C and 42 degrees C for 10 and 20 min. The number of surviving mycelia on the agar blocks was determined from the standard curves of the colony diameter and original inocula of the conidia. At the same time, the thermal effect on the cellular morphology was examined using SEM. Most fungal mycelia (99.7%) were killed after treatment at 42 degrees C for 20 min without essential oil. The fungicidal activity of essential oils was markedly enhanced by treating at 42 degrees C for 20 min as compared with that at 27 degrees C, showing 1/4 - 1/32-fold reduction of minimum fungicidal concentration (MFC to kill 99.99%). The order of the fungicidal activity of 11 essential oils was oregano, thyme thymol, cinnamon bark > lemongrass > clove, palmarose, peppermint, lavender > geranium Bourbon, tea tree > thyme geraniol oils. MFCs were further reduced to 1/2 - 1/8 by the addition of 10% sodium chloride. The salt effect was explained, at least partly, by an increase in mycelial adsorption of antifungal constituents in the presence of sodium chloride. Considerable hyphal damage was done at 27 degrees C by the essential oils, but no further alteration in morphology of the hyphae treated at 42 degrees C with or without oil was observed by SEM. The inhibitory effect of heat and oils was also observed against mycelia of T. rubrum and conidia of T. mentagrophytes. Thermotherapy combined with essential oils and salt would be promising to treat tinea pedis in a foot bath.

Hyperthermic treatment of chromomycosis with disposable chemical pocket warmers. Report of a successfully treated case, with a review of the literature

A case of chromomycosis in which hyperthermia proved effective is reported. The patient was a 56-year-old male bean curd maker who, without any previous history of minor trauma, developed on the extensor side of the left upper arm an eczematous lesion that underwent gradual radial expansion. The lesion showed a well-defined, 7 x 10 cm infiltrated erythematous plaque with the central area healed and, at the upper and lower borders, adherent scales and crusts on the surface. Histological examination revealed granulomatous changes in the dermis, as well as sclerotic cells within giant cells and microabscesses. On culturing, Fonsecaea pedrosoi was isolated. The patient was treated with disposable chemical pocket warmers, which were secured over the lesion with a rather tight elastic bandage, so that they kept the affected area warm for 24 hours a day. After a month of such hyperthermic treatment, the erythema and infiltration had decreased considerably, and microscopic examination and culture of the crusts both yielded negative results. Examination of biopsy specimens of the lesion after the third month showed that it had cicatrized. The treatment was stopped after 4 months, and no relapse occurred. We also summarize the published results of local hyperthermic treatment of chromomycosis in Japan.

Hyperthermic treatment of sporotrichosis: experimental use of infrared and far infrared rays

We used pocket warmers and infrared and far infrared rays to treat 14 cases of sporotrichosis, 7 in children and 7 in adults. There were 9 cases of the fixed cutaneous type and 5 of the lymphocutaneous type; 6 were located on the face and 8 on the limbs. Four cases were treated with pocket warmers, 5 with infrared rays, and 5 with far infrared rays. All lesions treated with pocket warmers were facial lesions in children; infrared and far infrared ray treatments were used in 3 children and 7 adults, 2 on facial lesions and 8 on lesions on the extremities. In treatments with infrared and far infrared rays, the amount of heat was greater than with the pocket warmers, and one 15-min treatment daily was sufficient to yield satisfactory results, but this method is difficult to use on children and on the face, and 40-min treatments two or three times a week proved unsatisfactory. Infrared and far infrared ray treatments allow the length of a single treatment to be reduced by three-quarters, in comparison with one pocket warmer treatment.

Ultrastructure of Sporothrix schenckii treated with iodine-potassium iodide solution

The ultrastructural changes produced by iodine-potassium iodide solution on yeast cells of Sporothrix schenckii were investigated by transmission electron microscopy in order to clarify the mechanism of oral potassium iodide therapy for sporotrichosis. Yeast cells were dipped with solutions containing various concentrations of iodine. The rate of germination decreased markedly between the range of iodine concentrations from 0.63 microgram/ml to 5.0 micrograms/ml. No significant ultrastructural changes were seen at the concentration of the iodine of 1.25 microgram/ml (80% germination) or less. In the concentration of 2.5 micrograms/ml (50% germination), normal cells and degenerated cells coexisted. When the cells were treated with 5.0 micrograms of iodine per ml (0% germination) or more, their interior structures were completely destroyed. It is assumed that iodine treatment of the organism causes rapid destruction in the whole cell.

Effects of hyperthermia on phagocytosis and intracellular killing of Sporothrix schenckii by polymorphonuclear leukocytes

The effects of hyperthermia on phagocytosis and killing of Sporothrix schenckii by polymorphonuclear leukocytes (PMNs) were investigated in order to clarify the mechanism of local thermotherapy for sporotrichosis. Yeast cells of S. schenckii, PMNs and serum were incubated at 37 degrees C or 40 degrees C for 2 or 4 hours. Rate of phagocytosis and killing rate (rate of germination) were estimated, and their processes were observed by transmission electron microscopy. There was no effect of hyperthermia on the phagocytosis rate, but the killing rate increased significantly at 40 degrees C. Electron microscopic examination showed an increase of granularity in the yeast cytoplasm, elongation and fragmentation of the cell membrane. The ultrastructural changes were basically identical under both temperatures, but the degree of these changes was higher at 40 degrees C than at 37 degrees C. Although both intact and degenerated yeasts were found in the same conditions, their transient forms were few, suggesting that the PMN-killing process was completed promptly.