Progression of interdigital infections from simplex to complex.

The dynamics of symptomatic toe web infections often involve an ecologic interplay in which an initial dermatophyte infection provides a hospitable niche for subsequent colonization by bacteria. Several studies suggest that exacerbation of a mild dermatophyte infection (dermatophytosis simplex) can arise in the occlusive environment of the toe web space. Fungal infection induces damage to the stratum corneum, which allows overgrowth of resident bacteria and maceration, itching, and often malodor at the site (dermatophytosis complex). Because fungi frequently elaborate antibacterial substances, the superinfecting bacteria generally are resistant to penicillin and other antibiotics. A flourishing bacterial superinfection may mask the underlying fungal cause, making it difficult to obtain a positive fungal culture.