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Mild Positive Pressure Improves the Efficacy of Benzalkonium Chloride against Staphylococcus aureus Biofilm
Shamaila Tahir1, Sarah Emanuel1,2, David W Inglis2
1Surgical Infection Research Group, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, NSW 2109, Australia.
Abstract:
Current protocols using liquid disinfectants to disinfect heat-sensitive hospital items frequently fail, as evidenced by the continued isolation of bacteria following decontamination. The contamination is, in part, due to biofilm formation. We hypothesize that mild positive pressure (PP) will disrupt this biofilm structure and improve liquid disinfectant/detergent penetration to biofilm bacteria for improved killing. Staphylococcus aureus biofilm, grown on polycarbonate coupons in the biofilm reactor under shear at 35 °C for 3 days, was treated for 10 min and 60 min with various dilutions of benzalkonium chloride without PP at 1 atmosphere (atm), and with PP at 3, 5, 7, and 10 atm. The effect on biofilm and residual bacterial viability was determined by standard plate counts, confocal laser scanning microscopy, and scanning electron microscopy. Combined use of benzalkonium chloride and PP up to 10 atm significantly increased biofilm killing up to 4.27 logs, as compared to the treatment using disinfectant alone. Microscopy results were consistent with the viability plate count results. PP improved disinfectant efficacy against bacterial biofilm. The use of mild PP is possible in many flow situations or if equipment/contaminated surfaces can be placed in a pressure chamber.
Insights
Mild positive pressure (PP) enhances disinfectant effectiveness against bacterial biofilms on heat-sensitive medical items. This method significantly improves bacterial killing, addressing a critical gap in hospital disinfection protocols.
Area of Science:
- Microbiology
- Biomedical Engineering
- Infectious Disease Control
Background:
- Liquid disinfectants often fail to eliminate bacterial biofilms on heat-sensitive hospital items.
- Biofilm formation on medical equipment poses a significant challenge to effective decontamination.
- Current disinfection protocols struggle with residual bacterial contamination.
Purpose of the Study:
- To investigate if mild positive pressure (PP) can disrupt bacterial biofilms.
- To determine if PP enhances the efficacy of liquid disinfectants against biofilms.
- To improve bacterial killing in hospital item disinfection.
Main Methods:
- Cultured *Staphylococcus aureus* biofilms on polycarbonate coupons.
- Treated biofilms with benzalkonium chloride disinfectant at various dilutions and pressures (1-10 atm).
- Assessed biofilm disruption and bacterial viability using plate counts, confocal laser scanning microscopy, and scanning electron microscopy.
Main Results:
- Combined benzalkonium chloride and PP significantly increased biofilm killing by up to 4.27 logs compared to disinfectant alone.
- Microscopy confirmed improved disinfectant penetration and bacterial killing under PP.
- Positive pressure demonstrated enhanced disinfectant efficacy against bacterial biofilms.
Conclusions:
- Mild positive pressure is a viable strategy to enhance disinfectant efficacy against bacterial biofilms.
- This approach can significantly improve the decontamination of heat-sensitive hospital items.
- PP can be integrated into flow systems or pressure chambers for effective disinfection.
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