Frequent isolation of Arthroderma benhamiae from dogs with dermatophytosis

Molecular analysis methods have led to many changes in the taxonomy of dermatophyte species.

We hypothesized that fungi displaying morphology consistent with a traditional identification of 'Trichophyton mentagrophytes' represent multiple species, consistent with the new taxonomy.

Fungal specimens (n = 20) were collected directly from animals with dermatophytosis, were among those submitted for diagnostic analysis or were part of historical teaching collections. Primers that amplified a portion of the 28S ribosomal RNA gene and primers specific for a fragment from the internal transcribed spacer region were used for PCR amplification of genomic DNA. The DNA sequences from the amplified products were compared with databases to identify the isolates.

Of the 80% (n = 16) of the fungal isolates identified as Arthroderma benhamiae, eight were collected from dogs. One isolate was identified as Arthroderma vanbreuseghemii, two were Trichophyton erinacei and one was Nannizziopsis (Chrysosporium) guarroi, which was probably present as a saprophyte.

Frequent isolation of A. benhamiae from dogs suggests a greater host range for this fungus than reflected in the current literature. Our data also suggest the potential for geographical restriction of strain types within the species. Efforts to identify fungal isolates using molecular techniques create a better understanding of diversity and epidemiology of the dermatophytes.