Efficacy of nonantimicrobial drugs against Enterococcus faecalis using confocal laser scanning microscopy – An in vitro study

Abstract Background: Enterococcus faecalis is a key contributor to persistent endodontic infections and often shows resistance to conventional medicaments such as calcium hydroxide. Growing antimicrobial resistance has led to interest in repurposing nonantibiotic drugs such as nonsteroidal anti-inflammatory drugs and proton-pump inhibitors that have shown promising antimicrobial effects against E. faecalis . Aim: The study aimed to evaluate the in vitro antibiofilm activity of different combinations of nonantimicrobial drugs with and without calcium hydroxide against E. faecalis . Materials and Methods: Dentin specimens were infected with E. faecalis for 14 days to allow biofilm formation, then exposed to test solutions for 7 days. Eight groups were evaluated; untreated control, calcium hydroxide, diclofenac sodium, Omeprazole, their combinations in distilled water, and their combinations with calcium hydroxide. Confocal laser scanning microscopy was used for E. faecalis biofilm quantification, indicated as the percentage of green population (live cells), reduction percentage, and log 10 total biovolume. Statistical analysis included Dunn’s multiple comparison. The green percentage and reduction percentage were compared using Tukey’s post hoc test. Results: All treatments reduced viability, with Diclofenac sodium and Omeprazole combination showing the greatest effect, lowering viable cells to 32.82% ± 7.23% (54.97% ± 9.71% reduction percentage; P < 0.0001). Conclusions: Overall, the Diclofenac sodium–Omeprazole combination in distilled water was the most effective against E. faecalis biofilm, highlighting its potential in managing such persistent infections. With more extensive research, it could play a meaningful role in addressing antimicrobial resistance.