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.