Halicin Is Effective Against Staphylococcus aureus Biofilms In Vitro

Area of Science:

• Microbiology
• Infectious Diseases
• Pharmacology

Background:

• Bacterial biofilms pose challenges in treating orthopaedic infections due to inherent antibiotic resistance.
• Halicin demonstrates potent activity against planktonic bacteria, including drug-resistant strains and quiescent bacteria, but its effect on biofilms is unknown.

Purpose of the Study:

• To evaluate Halicin's efficacy against Staphylococcus aureus biofilms of varying maturity.
• To compare Halicin's biofilm activity with conventional antibiotics used for orthopaedic infections.

Main Methods:

• Minimal Biofilm Eradication Concentrations (MBEC75) were determined for 3-day and 7-day S. aureus biofilms using 96-well peg plates.
• Biofilm viability was assessed via resazurin reduction or colony-forming unit counts.
• Minimum Inhibitory Concentrations (MICs) were determined for planktonic bacteria.

Main Results:

• Halicin exhibited equivalent efficacy against planktonic S. aureus and 3-day biofilms (25 μM).
• Eightfold higher Halicin concentrations (200 μM) were required for 7-day biofilms.
• Conventional antibiotics showed significantly reduced efficacy against mature biofilms compared to planktonic forms.

Conclusions:

• Halicin is effective against S. aureus in less mature biofilms, comparable to its planktonic activity.
• Increased concentrations of Halicin are necessary for efficacy against mature biofilms.
• Halicin presents a promising therapeutic option for S. aureus orthopaedic infections, warranting further investigation in animal models and combination therapies.