Effect of a bacterial glutaminyl cyclase inhibitor on multi-species-biofilms

Modifying bacterial virulence could be an interesting alternative to antibiotics. The study aimed to examine the effects of an inhibitor targeting bacterial glutaminyl cyclase [which is selectively present in Porphyromonas gingivalis (Pg), Tannerella forsythia (Tf), and Prevotella intermedia (Pi)] on various multispecies biofilms.

Two multi-species biofilms-one containing four species (including Tf) and another with 12 species (including Tf, Pg, and Pi)-were cultured in the presence of 31.25-500 µM of a [4,5-c]pyridine-based inhibitor. After 24 h, bacterial counts, biofilm biomass, metabolic activity, and, when Pg was included, Arg-gingipain activity were measured. Additionally, the biofilms were exposed to monocytic cells; here, the release of interleukin (IL)-1β and IL-10 was analyzed. The data were analyzed using a one-way analysis of variance (ANOVA) with a post-hoc comparison performed using the Bonferroni correction.

In all biofilms, total bacterial counts and those of Pg and Tf remained unaffected by the inhibitor. In the 12-species biofilm, both biomass and total metabolic activity decreased at high inhibitor concentrations (500 µM to 75.2 ± 6.5% and 87.2 ± 5.8%, respectively; each p < 0.001). The arginine-specific amidolytic activities of Rgp declined dose-dependently, down to 60.4 ± 10.2% (p < 0.001) at 500 µM of the inhibitor. Consequently, Pg colonies lost pigmentation as inhibitor concentrations increased. The inhibitor also reduced IL-1β release from monocytic cells stimulated by the 12-species biofilm. The studied [4,5-c]pyridine-based inhibitor is able to modify virulence of a multispecies biofilm. It might have the potential to be a promising approach in periodontal prevention and therapy.