Morphological and physiological features of Arthroderma benhamiae anamorphs isolated in northern Germany

The anamorph of Arthroderma benhamiae is an upcoming zoophilic dermatophyte that only in recent years has gained importance as a cause of tinea in humans. Its identification by conventional methods can cause problems. In this study we have subjected seven genetically confirmed strains of A. benhamiae anamorphs from northern Germany recently identified in our laboratory to a comprehensive assessment. Their macroscopic and microscopic morphology was checked on various agars and enzyme release stimulated by substrates with keratin, hair perforation and other physiological characteristics were tested. All strains were related to the previously described yellow phenotype of the A. benhamiae anamorph and showed a high resemblance among themselves. Coherent features were their uniform thallus morphology on Sabouraud glucose agar with yellow pigmentation, the formation of circuit-like hyphal structures and hyphal connections that had not been described previously, a lack of conidia, thiamine dependence, the spectrum of released enzymes and a good growth on human stratum corneum. With exception of the latter two these criteria are suggested for the identification of this anamorph phenotype that should be evaluated by future observations. Different phenotypes of the A. benhamiae anamorph may prevail in other geographic regions.