16S rDNA sequencing and metadata of Dutch dental unit water

The consistent application of hydrogen peroxide controls biofilm growth and removes Vermamoeba vermiformis from multi-kingdom in-vitro dental unit water biofilms

The water systems inside a dental unit are known to be contaminated with a multi-kingdom biofilm encompassing bacteria, fungi, viruses and protozoa. Aerosolization of these micro-organisms can potentially create a health hazard for both dental staff and the patient. Very little is known on the efficacy of dental unit disinfection products against amoeba. In this study we have examined the effect of four different treatment regimens, with the hydrogen peroxide (H₂O₂) containing product Oxygenal, on an in-vitro multi-kingdom dental unit water system (DUWS) biofilm. The treatment efficacy was assessed in time using heterotrophic plate counts, the bacterial 16S rDNA, fungal 18S rDNA gene load and the number of genomic units for Legionella spp. the amoeba Vermamoeba vermiformis. The results indicated that a daily treatment of the DUWS with a low dose H₂O₂ (0.02% for 5 h), combined with a weekly shock dose (0.25% H₂O₂, 30 min) is necessary to reduce the heterotrophic plate count of a severely contaminated DUWS (>10⁶ CFU.mL^-1) to below 100 CFU.mL^-1. A daily treatment with a low dose hydrogen peroxide alone, is sufficient for the statistically significant reduction of the total amount of bacterial 16S rDNA gene, Legionella spp. and Vermamoeba vermiformis load (p < 0.005). Also shown is that even though hydrogen peroxide does not kill the trophozoite nor the cysts of V. vermiformis, it does however result in the detachment of the trophozoite form of this amoeba from the DUWS biofilm and hereby ultimately removing the amoeba from the system.

Short-chain fatty acids regulate B cells differentiation via FFAR2 to alleviate rheumatoid arthritis

BACKGROUND AND PURPOSE

Short-chain fatty acids (SCFAs) are metabolites of gut microbes involved in the host's inflammatory response and immunity. The aim of this study was to investigate the role of SCFAs in RA and the possible mechanisms.

EXPERIMENTAL APPROACH

Gut microbiota diversity in mice was analysed by 16S rDNA sequencing. SCFAs levels were analysed by gas chromatography mass spectrometry. T cells and B cells were analysed by flow cytometry. Bone damage was analysed by micro-CT and x-ray. Histopathological status was analysed by HE staining. The protein in tissues were analysed by immunohistochemistry and PCR. Mice with CD19⁺ B cells specifically deficient in FFAR2 were used to explore the molecular mechanisms involved.

KEY RESULTS

Levels of acetate, propionate, butyrate, and valerate were decreased in RA patients, and the first three levels correlated positively with the frequency of Bregs in peripheral blood but not with Tregs. Administration of the three SCFAs prior to the onset of collagen-induced arthritis in mice improved arthritic symptoms, increased the Bregs frequency, and decreased transitional B cells and follicular B cells frequency. However, the preceding phenomena could not be observed in mice with CD19⁺ B cells deficient in FFAR2. The effects of the three SCFAs in RA were dependent on FFAR2 while were independent of the other five B cell receptors (FFAR3, GPR109A, PPARγ, Olfr-78, and AhR).

CONCLUSIONS AND IMPLICATIONS

SCFAs regulate B cells differentiation via FFAR2 to alleviate RA. This will provide new insights into the treatment of RA from an immunological and microbiological perspective.