Time-kill curve analysis of fucoidan combination with conventional antibiotics against biofilms formation of methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii clinical isolates.

Introduction This study investigates the efficacy of fucoidan, both alone and in combination with antibiotics, against single-species biofilms and mixed-species, individual planktonic, and co-culture planktonic conditions of Methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii. Materials and Methods Fucoidan, a sulfated polysaccharide, was purchased from Sigma-Aldrich, USA. Clinical isolates of MRSA and A. baumannii were obtained from diabetic foot ulcers (DFUs), and single-species biofilms and mixed-species biofilms were developed to assess susceptibility to the treatments using MIC, MBC, MBIC, MBEC, and time-kill kinetics assays. Cytotoxicity was assessed using MTT assays on human skin fibroblast cells (HSF-PI 16). Results The study determined the geometric mean MIC and MBC values for gentamicin, imipenem, and fucoidan in MRSA and A. baumannii cultures, both individually and in co-culture. The MIC and MBC values were significantly lower under co-culture conditions, indicating enhanced antimicrobial efficacy. Synergy between fucoidan, gentamicin, and imipenem was confirmed through time-kill assays, which showed complete inhibition of bacterial growth and effective biofilm eradication, particularly in mixed-species biofilms. Fucoidan demonstrated low cytotoxicity at optimal concentrations, highlighting their potential as a therapeutic strategy against biofilm-associated infections in diabetic foot ulcers. Conclusion The study concludes that fucoidan, in combination with gentamicin and imipenem, effectively disrupts mixed-species biofilms of MRSA and A. baumannii, suggesting fucoidan-based therapies could improve outcomes for DFU patients, warranting further clinical investigation.