Comparing the Composition of Cutaneous Microbiota on the Plantar Surface and Interdigital Spaces of the Diabetic and Non-diabetic Foot

Introduction: The skin is an ecosystem that contains a wide variety of micro-organisms. Alterations in the cutaneous microbiome not only disrupt the host-microbe relationship but can permit unchecked cutaneous colonization by pathogens.

The aim of this study was to determine if there is a detectable difference in the microbiome between people with and without diabetes that could be a contributing factor in the development of skin and soft tissue infections in people with diabetes.

Methods: This single center, analytical, cross-sectional study compared the cutaneous microbiome of the right plantar forefoot and interdigital spaces of clinic patients with and without diabetes. Skin swabs were analyzed using Next Generation Sequencing (NGS) to identify and quantify all bacterial and fungal sequences.  

Results: Data showed that all patients harbor a diverse microbiome of both bacteria and fungi. The most abundant bacterial species were Staphylococcus pettenkoferi (29.7%) and Staphylococcus hominis (7.9%). The two most abundant fungal species, Ascomycota sp. (13.6%) and Fungi sp. (12.5%), have not been previously described and could only be identified to the phylum and kingdom level, respectively. In both cohorts, 100% of the samples had bacterial dermal pathogens present, and 90% showed fungal pathogens at different degrees of relative abundances. In gastrointestinal health, a high degree of diversity is a marker for a healthy microbiome, but in this data set, 73% of samples showed either a bacterial or fungal overgrowth, where one species represented more than 50% of the bacterial or fungal composition, (37% and 17% respectively), or overgrowth in both (20%).

Conclusions: This study highlighted the complexity of the human cutaneous microbiome. Having a pathogen present in the microbiome, did not indicate a disease state or warrant antibiotic treatment. Further understanding of the human cutaneous microbiome will improve our understanding of skin health management strategies to help prevent the development of diabetic foot skin and soft tissue infections and ulcerations.