Commensal Bacteria Augment septic Arthritis in a Dose-Dependent Manner.

Background: Septic arthritis is considered one of the most dangerous joints diseases and is mainly caused by the Gram-positive bacterium (). Human skin commensals are known to augment infections. The aim of this study was to investigate if human commensals could augment -induced septic arthritis.

Method: NMRI mice were inoculated with alone or with a mixture of together with either of the human commensal () or (). The clinical, radiological and histopathological changes due to septic arthritis were observed. Furthermore, the serum levels of chemokines and cytokines were assessed.

Results: Mice inoculated with a mixture of and or developed more severe and frequent clinical arthritis compared to mice inoculated with alone. This finding was verified pathologically and radiologically. Furthermore, the ability of mice to clear invading bacteria in the joints but not in kidneys was hampered by the bacterial mixture compared to alone. Serum levels of monocyte chemoattractant protein 1 were elevated at the early phase of disease in the mice infected with bacterial mixture compared with ones infected with alone. Finally, the augmentation effect in septic arthritis development by was bacterial dose-dependent.

Conclusion: The commensal bacteria dose-dependently augment -induced septic arthritis in a mouse model of septic arthritis.