Effects of Postbiotics Derived from Lactobacillus plantarum and Bifidobacterium bifidum on Biofilm Formation and Virulence Gene Expression of Enterococcus faecalis

Enterococcus faecalis is a Gram-positive opportunistic pathogen that is capable of forming biofilms and developing antibiotic resistance, complicating the treatment of infections. This study investigates the effect of postbiotics derived from Lactobacillus plantarum and Bifidobacterium bifidum on biofilm formation and virulence gene expression in E. faecalis . In this study, standard strains L. plantarum ATCC 8014, B. bifidum ATCC 15696 and E. faecalis ATCC 29212 were used. Postbiotics/cell-free supernatant (CFS) was prepared from probiotics and added to E. faecalis . Biofilm formation was examined by microtiter plate method and expression of Ebp , efa , Asa and Ace genes was assessed by quantitative Real-time PCR. Statistical analysis was performed using Student's t-test and ANOVA (p < 0.05). CFSs significantly reduced biofilm formation in a dose-dependent manner. B. bifidum CFSs at 20 mg/mL (p < 0.0001), 10 mg/mL (p < 0.0001), and 5 mg/mL (p = 0.04) significantly decreased biofilm formation compared to the control. Similarly, L. plantarum CFSs at 20 mg/mL (p = 0.003) and 10 mg/mL (p = 0.01) showed a significant inhibitory effect. qRT-PCR analysis revealed that L. plantarum CFSs downregulated efa (p < 0.0001), Asa (p = 0.01), and Ace (p = 0.001) genes but had no effect on the Ebp gene. Conversely, B. bifidum CFSs reduced Ebp (p = 0.0003) and Ace (p = 0.0001) genes but did not significantly alter efa and Asa genes. These findings suggest that postbiotics could be used as a potential alternative to reduce the pathogenicity of E. faecalis , although further clinical trials are necessary to confirm these results.