Antimicrobial effects of positively charged surfaces on adhering Gram-positive and Gram-negative bacteria

Area of Science:

• Biomaterials Science
• Microbiology
• Surface Chemistry

Background:

• Biomaterial infection involves bacterial adhesion and surface growth.
• Understanding surface charge effects on bacterial behavior is crucial for developing infection-resistant materials.

Purpose of the Study:

• To compare the antimicrobial effects of positively and negatively charged poly(methacrylate) surfaces on adhering bacteria.
• To investigate the influence of surface charge on bacterial adhesion and subsequent surface growth.

Main Methods:

• Bacterial adhesion and surface growth assays were performed using Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa.
• Experiments utilized a parallel plate flow chamber with surfaces of varying charge (positive +12 mV, negative -12 mV, and highly negative -18 mV).
• Bacterial adhesion was measured initially, followed by monitoring surface growth after perfusion with growth medium.

Main Results:

• All tested bacteria exhibited the most rapid initial adhesion to the positively charged surface.
• Gram-negative bacteria (E. coli, P. aeruginosa) showed no surface growth on the positively charged surface.
• Both Gram-positive and Gram-negative bacteria demonstrated exponential surface growth on negatively charged surfaces, despite slower initial adhesion.

Conclusions:

• Positively charged biomaterial surfaces demonstrate an antimicrobial effect against adhering Gram-negative bacteria.
• The surface charge of biomaterials significantly influences bacterial adhesion and subsequent growth dynamics.
• Positively charged surfaces may offer a strategy for preventing Gram-negative bacterial infections on biomaterials.