Low-Molecular-Weight Branched Polyethylenimine Potentiates Ampicillin against MRSA Biofilms

Area of Science:

• Microbiology
• Biotechnology
• Materials Science

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) is a global health threat, particularly in device-related infections and chronic wounds.
• MRSA's robust biofilm formation confers resistance to most available antibiotics, necessitating novel therapeutic strategies.
• Previous research indicated the potential of branched polyethylenimine (BPEI) as an antibiotic potentiator against Staphylococcus epidermidis biofilms.

Purpose of the Study:

• To investigate the efficacy of 600 Da BPEI as a potentiator for antibiotic treatment against MRSA biofilms.
• To elucidate the mechanism of action for the synergistic effect between BPEI and ampicillin in eradicating MRSA biofilms.

Main Methods:

• Utilized microtiter minimum biofilm eradication concentration models to assess treatment efficacy.
• Quantified biofilm biomass using crystal violet assays.
• Visualized biofilm structure and bacterial morphology via electron microscopy.

Main Results:

• Demonstrated synergistic eradication of MRSA biofilms by combining BPEI and ampicillin.
• Identified a two-step mechanism: BPEI first removes extracellular polymeric substances (EPS), exposing bacteria.
• Observed electrostatic interaction between BPEI and bacterial cell wall teichoic acid, enhancing ampicillin's efficacy.

Conclusions:

• BPEI acts as a potent sensitizer for ampicillin against MRSA biofilms.
• The combined approach offers a promising strategy for combating difficult-to-treat MRSA infections.
• Understanding the synergistic mechanism provides a foundation for developing new anti-biofilm therapies.