The effects of temperature, incubation atmosphere, and medium composition on arthrospore formation in the fungus Trichophyton mentagrophytes

Abstract

Several growth conditions were found to allow abundant arthrospore formation in T. mentagrophytes. These included growth at 32--37 degrees C on Sabouraud's medium (1% neopeptone, 4% glucose) and growth at temperatures below 32 degrees C solely on neopeptone or other complex peptide sources without the addition of glucose, a supplementary carbon source. Sabouraud's medium did not allow arthropsore formation at 30 degrees C under normal atmospheric conditions. However, if oxygen tension were reduced by partial replacement of air with either N2 or CO2 arthrosporulation did occur on Sabouraud's medium at 30 degrees C. The rate of germ tube elongation was lower under those conditions which supported arthrospore formation, suggesting a correlation between decreased rate of hyphal extension and arthrospore formation. Stimulation of arthrospore formation by sublethal concentrations of several antifungal agents tends to support this hypothesis.

Arthroconidia production in Trichophyton rubrum and a new ex vivo model of onychomycosis

“…Similar effects have been seen in T. mentagrophytes, in which griseofulvin (0?5 mg ml 21 ), clotrimazole (0?1 mg ml 21 ), and particularly amphotericin B (5 mg ml 21 ), stimulate a low level of arthrosporulation (Emyanitoff & Hashimoto, 1979). Compared to other antifungals, itraconazole, and particularly terbinafine, have significantly increased rates of cure and shorter treatment times (Roberts, 1999), and interestingly, in our study, only itraconazole, and particularly terbinafine, suppressed arthroconidium production in T. rubrum N250.…”

“…At 42 u C, no growth occurred. Temperatures between 32 and 39 u C also strongly favour the arthroconidiation of T. mentagrophytes on SDA, and no or less arthroconidium formation is seen in T. mentagrophytes at 30 u C (Emyanitoff & Hashimoto, 1979); in addition, arthroconidium formation in T. rubrum was seen at 37 u C but not at 25 u C by . The temperature required for optimal arthroconidium formation in vitro, 37 u C, is higher than those recorded for the surface of the human body, typically 33±1 uC, and near the upper limit for growth for this species.…”

“…Whether the stimulated arthroconidiogenesis is due to the presence of CO 2 itself or reduced oxygen tension has been the subject of some controversy (Barrera, 1986). Some investigators (Emyanitoff & Hashimoto, 1979) have shown that exogenous CO 2 is not the absolute requirement, and that replacement of air by either N 2 or CO 2 stimulates arthrosporulation in T. mentagrophytes to the same extent. However, King et al (1976) have shown that while helium and methane, like CO 2 , tend to inhibit the growth of T. mentagrophytes, they do not induce arthroconidial formation.…”

“…Arthroconidia shed from lesions are likely to be the form involved in the spread of infection. The development of arthroconidia in Trichophyton mentagrophytes has been observed in vitro by a number of authors (Bibel et al, 1979;Emyanitoff & Hashimoto, 1979;Weigl & Hejtmanek, 1979;Wright et al, 1984) and in Trichophyton rubrum (Miyaji & Fujiwara, 1971). Here we describe a detailed examination of the environmental and iatrogenic factors which affect arthroconidiation in vitro in T. rubrum, and describe a new ex vivo model for the study of arthroconidium formation in nails.…”

Effects of terbinafine exposure on the ultrastructure ofTrichophyton interdigitale

“…Arthroconidia were prepared as suspensions of single cells from 10-day-old cultures grown as surface lawns on glucose-peptone agar in an atmosphere of 10% CO 2, 90% 02 at 37°C [1,4]. Surface growth was harvested from the culture plates with a scalpel blade, suspended in 5 ml 1% Tween 80-distilled water and agitated on a vortex mixer for 5 min.…”