Background/Purpose: Gut, oral and genital mucosa microbiome studies in Behçet’s syndrome have shown heterogeneous results including reduced bacterial diversity and decrease in butyrate-producing bacteria. A role of microorganisms and/or microbial products in pathergy positivity was proposed based on decreased positivity after surgical cleaning and increased positivity when patient’s saliva and pneumococcal vaccine are applied to the pathergy site. We aimed to determine the skin microbiome of pathergy positive and negative patients with Behçet’s syndrome.

Methods: We compared the bacterial and fungal skin microbiome of 30 pathergy positive and 30 pathergy negative patients who were not treated with immunosupprresives. Skin samples were obtained by swabbing before the pathergy test and stored at -80^oC. The first 30 pathergy positive patients and 30 pathergy negative patients matched to the pathergy positive ones for demographic features were included. Samples were studied using 16S and 5.8S rRNA gene sequencing.

Results: Bacterial diversity within each group (alpha diversity) was similarly high in both groups. Beta diversity analysis revealed that the bacteria in the two groups were different from each other in terms of genus and species. The pathergy negative group was rich in Betaproteobacteria, Burkholderiales, and Ralstonia picketti, while the pathergy positive group showed enrichment in Nevskia soli, Staphylococcus haemolyticus, and Sphingomonas sanxanigenens.  Alpha diversity of fungal species was higher in the pathergy positive group. Beta diversity analysis showed that the fungi of both groups were similar. Pseudopezicula tracheiphila and Aspergillus heterocaryoticus were the most abundant fungi in the pathergy positive group, while Aspergillus subversicolor prevailed in the pathergy negative group.

Conclusion: The skin microbiota was different among pathergy positive and negative BS patients. Bacterial diversity was high and bacterial species were different among the two groups. Fungal diversity was higher in the pathergy positive group and there were similar fungi in terms of genus in both groups. The role of these differences in pathergy positivity needs to be further studied.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/skin-microbiome-shows-differences-between-pathergy-positive-and-negative-patients-with-behcets-syndrome/