Effects of three γ-alkylidene-γ-lactams on the formation of multispecies biofilms.

ABSTRACT

This study evaluated the inhibitory effects of lactams on Streptococcus mutans, Enterococcus faecalis, and Candida glabrata multispecies biofilm formation. γ-Alkylidene-γ-lactams 1, 2, and 3 [solubilized in 3.5% dimethyl sulfoxide (DMSO)] were tested. Glass coverslips were conditioned with either the lactams or 3.5% DMSO (control) for 1 h, inoculated with microbial cultures, and incubated for 48 h. To assess the effect of the lactams on biofilm formation, the following parameters were determined the biofilm biomass (by both crystal violet staining and protein determination); the amount of insoluble polysaccharides of the extracellular matrix; and the number of viable and total cells [by both colony-forming unit counting and quantitative real-time PCR (qPCR)]. Data were analysed using one-way anova and post-hoc Tukey tests. Lactams 1, 2, and 3 promoted a statistically significant reduction in the amount of biofilm biomass, but only lactam 3 resulted in a statistically significant reduction in the number of attached viable E. faecalis. Both total protein content and the amount of extracellular polysaccharides decreased significantly. The effects of γ-alkylidene-γ-lactams 1, 2, and 3 on the inhibition of multispecies biofilm formation were evident by their ability to reduce the amount of protein and extracellular polysaccharides.