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Tools for the Real-Time Assessment of a Pseudomonas aeruginosa Infection Model
Published on: April 6, 2021
Resistance to a polyquaternium-1 lens care solution and isoelectric points of Pseudomonas aeruginosa strains
Gerda M Bruinsma1, Minie Rustema-Abbing, Henny C van der Mei
1Department of Biomedical Engineering, University Medical Center Groningen and University of Groningen, The Netherlands.
Insights
Pseudomonas aeruginosa strains resistant to polyquaternium-1 show higher cell surface charge. This increased negative charge, indicated by a higher isoelectric point, likely prevents the disinfectant from entering the bacterial cell.
Area of Science:
- Microbiology
- Ophthalmology
- Material Science
Background:
- Pseudomonas aeruginosa is a common cause of contact lens-related infections.
- Polyquaternium-1 is a disinfectant used in lens care solutions.
- Bacterial surface properties can influence antimicrobial resistance.
Purpose of the Study:
- To investigate the relationship between cell surface characteristics and resistance to polyquaternium-1 in Pseudomonas aeruginosa.
- To determine if cell surface hydrophobicity or charge correlates with resistance to a specific lens care solution.
Main Methods:
- Isolated 11 Pseudomonas aeruginosa strains from various ophthalmic sources.
- Measured cell surface hydrophobicity using water contact angle.
- Determined cell surface charge via micro-electrophoresis across a pH range.
Main Results:
- Resistant strains exhibited a higher isoelectric point (4.0-5.5) compared to susceptible strains (1.3-1.9).
- Susceptible strains were more negatively charged than resistant strains.
- No correlation was found between cell surface hydrophobicity and resistance levels.
Conclusions:
- Bacterial cell surface charge, specifically a higher negative charge, is associated with resistance to polyquaternium-1.
- Electrostatic repulsion between the positively charged disinfectant and negatively charged bacterial surface may impede antimicrobial efficacy.
Objectives:
The aim of this study was to correlate the cell surface hydrophobicity and charge of various strains of Pseudomonas aeruginosa with their resistance to a polyquaternium-1 lens care solution.
Methods:
The 11 P. aeruginosa strains included were isolated from eyes, contact lenses, lens cases and lens care solutions. Cell surface hydrophobicities were determined from water contact angle measurements and surface charges were measured as a function of pH using particulate micro-electrophoresis.
Results:
Strains resistant to polyquaternium-1 had an isoelectric point (IEP; pH where the bacterial zeta potential is zero) ranging from 4.0 to 5.5, whereas susceptible strains were more negatively charged than resistant strains and had an IEP between 1.3 and 1.9. Water contact angles ranged from hydrophilic (34 degrees) to hydrophobic (124 degrees), without showing a relation with antimicrobial resistance.
Conclusions:
Results suggest that electrostatic repulsion between cationic molecules on the cell surface and quaternary ammonium compounds impedes the antimicrobial entering the cell.
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