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Antimicrobial effects of positively charged surfaces on adhering Gram-positive and Gram-negative bacteria
B Gottenbos1, D W Grijpma, H C van der Mei
1Department of Biomedical Engineering, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
Abstract:
The infection of biomaterials is determined by an interplay of adhesion and surface growth of the infecting organisms. In this study, the antimicrobial effects on adhering bacteria of a positively charged poly(methacrylate) surface (xi potential +12 mV) were compared with those of negatively charged poly(methyl methacrylate) (-12 mV) and a highly negatively charged poly(methacrylate) (-18 mV) surface. Initial adhesion of Staphylococcus aureus ATCC 12600, Staphylococcus epidermidis HBH(2) 102, Escherichia coli O2K2 and Pseudomonas aeruginosa AK1 to these surfaces was measured in a parallel plate flow chamber in phosphate-buffered saline. Adhering bacteria were allowed to multiply by perfusing the flow chamber with growth medium. All bacteria adhered most rapidly to the positively charged surface, but there was no subsequent surface growth of the Gram-negative strains. On the negatively charged surfaces, despite a slower initial adhesion, surface growth of the adhering bacteria was exponential for both Gram-positive and Gram-negative strains. These results suggest that positively charged biomaterial surfaces exert an antimicrobial effect on adhering Gram-negative bacteria, but not on Gram-positive ones.
Insights
Positively charged biomaterial surfaces inhibit growth of adhering Gram-negative bacteria, but not Gram-positive bacteria. This finding impacts biomaterial design for infection control.
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.