Time-Kill Curve Analysis of Fucoidan Combination with Conventional Antibiotics against Biofilms Formation of Methicillin-Resistant Staphylococcus aureus and Acinetobacter baumannii Clinical Isolates.

Abstract

Introduction: This study investigates the efficacy of fucoidan combination with antibiotics, against single-species biofilms and mixed-species, individual planktonic, and coculture planktonic conditions of Methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii by time-kill curve analysis.

Materials and methods: Fucoidan, a sulfated polysaccharide, was purchased from Sigma-Aldrich, USA. Clinical isolates of MRSA and A. baumannii from diabetic foot ulcers (DFUs) were used, and single-species biofilms and mixed-species biofilms were developed to assess susceptibility to the treatments using MIC, MBC, minimum biofilm inhibitory concentration, minimum biofilm eradication concentration, 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-cultures. 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 DFUs.

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.