News release

From: BMJ Group

Imbalances in the oral microbiome linked to symptomatic hand osteoarthritis

Changes in the bacteria of the mouth may affect the microbiome of gut to worsen inflammation and pain in hand arthritis

Specific imbalances and disruptions to the oral microbiome have been linked to symptomatic hand arthritis by a study published online in the open access journal RMD Open.

Its findings suggest that the microbial environment of the mouth may influence the disease process of hand arthritis which is associated with pain, stiffness and reduced grip strength and can severely impair quality of life. The oral microbiome plays a role in systemic inflammation and interacts closely with gut microbiome which is significantly associated with symptomatic hand arthritis.

To assess the role of the oral microbiome, saliva samples from 52 people with symptomatic hand arthritis recruited from a community-based osteoarthritis study and 712 people without the condition were analysed using ribosomal RNA gene sequencing.

Compared with samples taken from participants without hand arthritis, samples from participants with symptomatic hand arthritis showed significantly lower oral microbial richness and altered composition.

Specifically, the abundance of Trichococcus bacteria was significantly higher in the symptomatic hand arthritis samples and positively associated with severity of hand arthritis symptoms. Trichococcus abundance in the oral microbiome was also positively associated with the gut microbial tyrosine metabolism pathway – a metabolic pathway previously implicated in hand arthritis.

Samples from participants with symptomatic hand arthritis also displayed reduced oral-gut microbiome correlations compared with controls suggesting the balance between these two microbial communities was disrupted.

This is an observational study, and as such, can’t establish cause and effect. The authors highlight some limitations, most importantly, that the oral microbiome was profiled using16S rRNA gene sequencing, which provides taxonomic and compositional insights but lacks the resolution to identify specific bacterial species or strains, and the cross- sectional design meant a temporal or causal relationship between oral microbiome alterations and symptomatic hand arthritis could not be established.

Symptomatic hand arthritis was diagnosed at hand level rather than at the individual joint which may have introduced some misclassification, and the small sample size may limit statistical power and prevent detection of additional species with more modest associations with pathogenesis. Finally, although several known confounders were adjusted for, confounding from unmeasured variables cannot be excluded.

Nevertheless, the authors conclude that oral microbiome dysbiosis and disruption of the oral-gut microbiome network are associated with prevalent symptomatic hand arthritis and suggest a potential role of the oral-gut microbiome axis in SHOA pathogenesis.

“This study provides the first evidence linking oral microbiome alterations to symptomatic hand arthritis and highlights their correlation with gut microbiome dysbiosis, suggesting a potential role for the oral-gut microbiome axis in symptomatic hand arthritis pathogenesis,” they say.

Larger studies are needed to confirm these associations, and longitudinal cohort studies are required to determine whether these microbial changes precede development of symptomatic hand arthritis or are consequences of the disease.