Objectives: Diabetes is considered to be one of the most prevalent endocrine diseases worldwide. Chronic wounds are among the most devastating conditions these patients face along with kidney failure and vascular disease. Even small lesions can progress to an infected chronic wound, sometimes leading to amputation or death. Diabetic-related impairments that disturb an adequate immune response against pathogens are known to contribute to the progression of diabetic wounds. However, the database on skin microbial communities in diabetic patients has been lacking. We aimed to comparatively analyze the overall skin micro- and mycobiome between patients with diabetes and healthy individuals.
Methods: We obtained skin swab samples from the foot (sole, toe, and interdigital space) of 20 diabetic patients (DM) and 20 healthy controls (HC). Using a culture-independent sequencing method followed by direct DNA extraction and molecular PCR, taxonomic compositions of bacteria and fungi at stepwise level ranks were analyzed. The phylogenic markers used were the V3 to V4 regions of 16S rRNA genes and the internal transcribed spacer 2 regions for bacteria and fungi, respectively. 
Results: The Shannon Diversity Indexes (SDIs) of bacterial communities were 2.48±0.82 and 3.028±0.84 in DM and HC samples, respectively. The SDIs of fungal communities were 3.06±1.09 and 3.93±0.85 in DM and HC samples, respectively. The difference in SDIs between the two groups was statistically significant (p<0.01 in bacterial analysis and p<0.05 in fungal analysis). In beta-diversity analyses, samples in different groups showed a tendency to form different clusters. Additionally, HC samples tended to have more differentiated fungal communities than DM samples. 
Conclusion: We observed lower taxonomic diversity in the foot skin scales of diabetic patients. Further studies are needed to properly interpret these results. Our data provide a new insight into the micro- and mycobiome of diabetic patients, which might contribute to future investigations associated with diabetes-related chronic wounds, especially in the diabetic foot.

Analysis of the Microbiome and Mycobiome of Foot Skin in Patients with Diabetes Mellitus