Cutaneous Dysbiosis and Dermatophytosis: The Unexplored Link.

The skin, besides being the largest interface between the body and the external environment, also forms an ecological niche which is populated by almost a trillion microorganisms. These, collectively known as the cutaneous microbiome, form a dynamic yet well-controlled system that resists invasion by pathogenic microorganisms, functioning as the so-called 'microbiological barrier', modulating the body's immune response, indirectly playing a crucial role in the pathogenesis of several inflammatory diseases. The composition and complexity of the microbiome are yet to be fully understood. The term 'dysbiosis' originally was coined in 1908 for a change in the gut microbiome. The potential role of 'cutaneous dysbiosis' in human dermatophytic infections, especially in the backdrop of the current epidemic of chronic, recurrent and treatment-resistant dermatophytosis, is understandably a topic of interest. The purpose of this review was to assess all studies using culture-independent methods for analysing the skin microbiome in various dermatophyte infections. The PubMed and Google Scholar databases were searched using the terms 'microbiome', 'dysbiosis', 'dermatophytes', 'dermatophytosis' and 'tinea'. All studies involving the use of standard sequencing methods for the study of the microbiome in various dermatophytoses were included. A total of four studies assessing the local skin microbiome associated with dermatophytic infections were found-one for tinea capitis, one for onychomycosis (in both psoriatic and nonpsoriatic nails) and two studying patients of tinea pedis. The studies determined the microbiological patterns in patients and compared them with healthy individuals using sequencing methods. Significant differences in the species diversity and counts of the various microorganisms between patient and control groups were demonstrated in all. However, cross-sectional design and the absence of pre- and post-treatment data along with a limited sample size were the major limitations in all of them. No data regarding other forms of tinea, most importantly, tinea cruris, corporis, faciei, etc. were found. The existing studies demonstrate a change in the microbiome or dysbiosis associated with cases of dermatophytosis, but are inadequate to determine a causal association. The changes may also be wholly or partly attributed to the effect of the infection. Further longitudinal studies from different regions of the world, also involving other forms of dermatophytosis, are required to provide a clearer insight and a more representative picture.