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

Introduction 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. Methods 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. Results and Discussion 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.