Impact of emodin alone or in combination with ampicillin on methicillin-resistant Staphylococcus aureus biofilms in vitro

Methicillin-resistant Staphylococcus aureus (MRSA) is recognized as a significant global health concern. The development of resistance to a broad spectrum of antibiotics, particularly following biofilm formation, renders conventional therapeutic options for MRSA ineffective. Three MRSA clinical isolates were examined in vitro to assess their biofilm-forming capacity and the disruptive effects on pre-established biofilm (via crystal violet staining and scanning electron microscopy), and quantify extracellular DNA (eDNA) release after exposed to emodin alone or in combination with ampicillin. In addition, real-time PCR was employed to investigate the impact of emodin on the expression of biofilm-related genes in MRSA biofilms. The inhibitory effect of emodin on biofilm formation and disruption was observed in a dose dependent manner. The antagonistic activity of emodin in combination with ampicillin against MRSA biofilms was confirmed through adhesion assays. Real-time PCR analysis revealed that emodin, either alone or in combination with ampicillin, effectively downregulated the transcriptional levels of the biofilm-related genes fnbpB, clfA and atlA, but not icaA. In addition, drug treatment resulted in a significant reduction in eDNA release and protein contain in EPS (extracellular polymeric substances), which corresponded to the markedly decreased transcript level of atlA and fnbpB, respectively. These observations suggest that emodin, either alone or in combination with ampicillin, holds potential as a therapeutic approach for MRSA biofilm-related infections.