Question

Axial spondyloarthritis (axSpA) is a complex rheumatic disease, mainly manifested at the spinal column and symptomatic by pain in the lower back. The exact pathogenesis is still not fully understood. It is thought to be caused by a combination of genetic as well as environmental factors, with microbial influences currently discussed as relevant.

Microbiome analysis using NGS alone does not provide information about abundance or spatial distribution of bacterial species and thus does not allow identifying the key microorganisms in mixed biofilms. Novel techniques such as fluorescence in situ hybridization (FISH) allow a more detailed analysis of the architecture of subgingival bacterial plaque.

To gain validated and multidimensional insights into the microbiomes, the combination of two complementary analysis techniques was developed.

Aim was to shed light on the oral microbiota in patients with axSpA and possible association with disease activity / severity.

Methods

23 patients and 4 healthy controls were included. Oral biofilms were sampled using a carrier system that was placed in a periodontal pocket for 5 days. Carriers were embedded and consecutive sections were submitted to NGS analysis. Based on those results, FISH was performed using specific probes for two bacterial species identified as potentially interesting to the disease, to gain further insight into the spatial structures of the microbiomes and to confirm the results obtained by NGS.

Results

Distinct differences between four groups of axSpA patients and between patients and healthy controls were detected. It could be shown that the results of the NGS analysis agree with those of FISH, with a very high degree of agreement.

Conclusions

Using the two different molecular techniques, a comprehensive and detailed "landscape" of the oral microbiome could be provided and we succeeded in giving microbiome data by NGS a spatial resolution.

The microbial differences that were be detected, are to be linked to clinical data. Information on the spatial distribution of the bacteria visualised by FISH could be used to find key species and investigate interactions between oral bacteria