Sub-inhibitory Concentrations of Nitrofurantoin Modulate Enterococcus faecalis Biofilm Formation and Adherence in vitro

Abstract

     Biofilm formation interferes with Enterococcus faecalis infections. Modulating biofilm formation may aid in developing innovative treatment strategies for multidrug-resistant bacteria responsible for urinary tract infections (UTIs). This study aims to evaluate the effect of nitrofurantoin minimum inhibitory concentration (MIC) on E. faecalis biofilm formation and adherence. Midstream urine samples (78) were collected from patients with UTI. The biochemical tests and VITIK technology were used to identify the E. faecalis isolates. The MICs of nitrofurantoin were determined to evaluate the susceptibility of E. faecalis isolates. Biofilm levels to polystyrene and adherence to human oral mucosal epithelial cells (OMECs) in vitro were evaluated. The inhibition role of nitrofurantoin sub-MICs in biofilm formation and adherence was examined. The incidence of UTI infection with E. faecalis was 12.82%. The susceptibility of ten E. faecalis isolates to nitrofurantoin, and their biofilm formation varied. No significant relationship was observed between the susceptibility of the isolates to nitrofurantoin and their biofilm production (r: +0.37, P>0.05). Sub-MICs of nitrofurantoin (½ MIC and ¼ MIC) significantly decline bacterial biofilm formation and adherence to human OMECs (P < 0.05).  Nitrofurantoin sub-MICs reduce biofilm production and E. faecalis adherence to biotic and abiotic surfaces. This can help modulate treatment strategies in the future.