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 hours, bacterial counts, biofilm mass, 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 ‘mass” 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.