EDTA suppresses bacterial perseverance to 2-phenoxyethanol

Area of Science:

• Microbiology
• Cosmetic Science
• Antimicrobial Resistance

Background:

• Cosmetic products use preservatives to prevent microbial growth, but ingredient limitations and nutrient content can promote microbial survival.
• Bacterial perseverance, a non-genetic survival strategy, has been observed with antibiotics but not extensively studied with cosmetic preservatives.
• Single-cell analysis is crucial for understanding microbial responses to preservatives in complex formulations.

Purpose of the Study:

• To investigate bacterial perseverance in Staphylococcus ureilyticus exposed to the preservative 2-phenoxyethanol (PE) and the booster ethylenediaminetetraacetate (EDTA).
• To assess the impact of EDTA on PE-induced perseverance using single-cell analysis.
• To evaluate the role of EDTA in enhancing preservative efficacy by suppressing persevering subpopulations.

Main Methods:

• Time-lapse microscopy and microfluidic devices for single-cell analysis of Staphylococcus ureilyticus.
• Exposure of bacterial cultures to 2-phenoxyethanol (PE) alone and in combination with ethylenediaminetetraacetate (EDTA).
• Conventional time-kill assays and pedigree analysis to track bacterial division and survival.

Main Results:

• A subpopulation of Staphylococcus ureilyticus exhibited perseverance, dividing multiple times over 23.4 hours during 2-phenoxyethanol (PE) exposure.
• Pedigree analysis confirmed a non-mutational basis for this perseverance phenotype.
• Ethylenediaminetetraacetate (EDTA) significantly reduced single-cell division in the presence of PE, despite similar population-level kill curves.

Conclusions:

• Single-cell analysis reveals microbial behaviors masked in population-based assays, highlighting the importance of studying preservative efficacy at the individual cell level.
• Ethylenediaminetetraacetate (EDTA) acts as a preservative booster by enhancing the bactericidal effect of 2-phenoxyethanol (PE) and suppressing bacterial perseverance.
• These findings provide insights for improving the safety and effectiveness of preservatives in cosmetic products.