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Potassium loss from chlorhexidine-treated bacterial pathogens is time- and concentration-dependent and variable
Noelle H O'Driscoll1, Olga Labovitiadi, T P Tim Cushnie
1School of Pharmacy and Life Sciences, Research Institute for Health and Welfare, Robert Gordon University, Schoolhill, Aberdeen, AB10 1FR, UK, n.o-driscoll@rgu.ac.uk.
Abstract:
The membrane-active antimicrobial agent chlorhexidine is used extensively as an antiseptic during infection prophylaxis and treatment. Whilst known to induce membrane damage that results in loss of internal solutes from bacteria, the present study sought to determine the rate and extent of cytoplasmic potassium loss and whether any species-specific differences exist. Direct measurement of potassium was achieved using flame emission spectrophotometry. Exposure of selected species to minimum inhibitory (MIC) or minimum bactericidal concentration (MBC) resulted in solute loss that was both concentration and time dependent. Within 5-min treatment with MIC levels, losses of 3 % from P. aeruginosa, 9 % from E. coli, and 15 % from S. aureus were recorded, whilst at 5 % w/v chlorhexidine, elevated loss of 20, 28, and 41 % occurred, respectively. Nonlinear potassium release was evident from all species when treated with 5 % chlorhexidine over a 60-min period. After this contact time, potassium loss from E. coli and S. aureus rose to 93 or 90 %, respectively; in contrast, P. aeruginosa retained 62 % intracellular potassium. Results confirm lethal concentrations of chlorhexidine induce rapid and substantial loss of cytoplasmic potassium from common pathogens. However, bacterial responses vary between species and should be borne in mind when considering mechanism of action.
Insights
Chlorhexidine causes rapid potassium loss from bacteria, but the extent varies by species. This finding is crucial for understanding how this antiseptic works against different pathogens.
Area of Science:
- Microbiology
- Antimicrobial Agents
Background:
- Chlorhexidine is a widely used antiseptic for infection control.
- It is known to damage bacterial membranes and cause solute loss.
Purpose of the Study:
- To quantify the rate and extent of cytoplasmic potassium loss induced by chlorhexidine.
- To investigate species-specific differences in potassium efflux.
Main Methods:
- Bacterial species were exposed to chlorhexidine at minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations.
- Potassium loss was directly measured using flame emission spectrophotometry over time.
Main Results:
- Potassium loss was concentration and time-dependent.
- Significant potassium efflux was observed in *P. aeruginosa*, *E. coli*, and *S. aureus*.
- Species-specific differences were noted, with *P. aeruginosa* retaining more intracellular potassium than *E. coli* and *S. aureus* after 60 minutes.
Conclusions:
- Lethal concentrations of chlorhexidine induce rapid and substantial cytoplasmic potassium loss in common bacterial pathogens.
- Bacterial responses to chlorhexidine-induced potassium loss vary significantly between species.
- These species-specific differences are important for understanding the antimicrobial mechanism of action of chlorhexidine.
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