Berberine attenuates the pathogenicity of Enterococcus faecalis N9 by regulating virulence factors

Abstract:

[Background] Enterococcus faecalis is a major opportunistic pathogen that can cause infections in humans and various animals. However, due to its inherent drug resistance and the enhancing multi-drug resistance, the clinical treatment of E. faecalis infections faces severe challenges. [Objective] This study explored the effects of berberine (BBR) on the transcription of virulence factors and pathogenicity-related phenotypes of E. faecalis, aiming to provide a reference for the treatment of E. faecalis infections. [Methods] The two-fold dilution method was employed to determine the minimum inhibitory concentration (MIC) of BBR against E. faecalis N9. Subsequently, sub-inhibitory concentrations (1/2 MIC, 1/4 MIC, and 1/8 MIC) of BBR were used to treat E. faecalis N9. The transcription levels of virulence factors of E. faecalis N9 were determined by qPCR. Additionally, biofilm formation of the strain was evaluated through crystal violet staining, and the adhesion to the pig small intestinal epithelial cell line IPEC-J2 was analyzed via a cell adhesion test. A gelatin liquefaction test was conducted to examine the gelatin liquefaction ability of the strain. [Results] The MIC of BBR against E. faecalis N9 was 625 μg/mL. Treatment with sub-inhibitory concentrations (1/2 MIC and 1/4 MIC) of BBR significantly inhibited the transcription of fimbrium-related virulence factors (ebpA, ebpB, ebpC, ebpR, and rnjB), biofilm-related virulence factors (esp, ace, psr, srtA, and atn), and gelatin liquefaction-related virulence factors (fsrA, fsrB, fsrC, sprE, and gelE) of E. faecalis N9. Moreover, the treatment markedly reduced the biofilm formation, adhesion to IPEC-J2 cells, and the ability to liquefy gelatin of E. faecalis N9. [Conclusion] BBR could effectively inhibit the transcription of pathogenicity-related virulence factors as well as the biofilm formation, cell adhesion, and gelatin liquefaction of E. faecalis N9. These findings suggest that BBR might be a candidate for treating E. faecalis infections.