RAPA: a novel in vitro method to evaluate anti-bacterial skin cleansing products.

Area of Science:

• Microbiology
• Dermatology
• Product Development

Background:

• Predicting the clinical efficacy of antibacterial skin cleansers requires reliable pre-clinical in vitro methods.
• Current methods for evaluating antibacterial product efficacy in vitro are often inadequate for predicting real-world performance.

Purpose of the Study:

• To develop and validate a simple, rapid, and reproducible in vitro method for assessing the efficacy of antibacterial skin cleansing products.
• To establish a pre-clinical assay that correlates with in vivo clinical outcomes for antibacterial skin cleansers.

Main Methods:

• A novel Rapid Agar Plate Assay (RAPA) was developed, using bacteriological agar as a surrogate for skin.
• Trypticase soy agar plates were washed with test products, rinsed, air-dried, inoculated with bacteria (Staphylococcus aureus or Escherichia coli), and incubated.
• The method combined elements of clinical Agar Patch and Cup Scrub assays to simulate hand washing.

Main Results:

• RAPA demonstrated a strong linear relationship between bacterial dose and percent reduction for antibacterial bar soap against S. aureus (R² = 0.97).
• A similar dose-response relationship was observed for antibacterial liquid hand soap against E. coli (R² = 0.96).
• The assay successfully differentiated antibacterial products based on active ingredient type and concentration, with results comparable to clinical methods.

Conclusions:

• The Rapid Agar Plate Assay (RAPA) is a simple, rugged, and reproducible in vitro method for evaluating antibacterial skin cleansing product efficacy.
• RAPA shows promise for predicting clinical efficacy, offering a valuable tool for the development of new antibacterial skin cleansers.
• Further research is recommended to enhance the clinical predictability of the RAPA method.