Plasmid Curing in Antibiotic- Resistant Escherichia coli Isolated from Herbal Cosmetic Powders

Antibiotic resistance, largely driven by plasmid-mediated genes, is a growing public-health threat, yet the presence of resistant bacteria in herbal cosmetic powders remains underexplored, creating a critical research gap in the safety of widely used natural products. This study aimed to isolate Escherichia coli from commonly used herbal cosmetic powders and evaluate the effectiveness of plasmid curing using sodium dodecyl sulfate (SDS) and heat-shock treatment. E. coli strains were isolated from Multani Mitti, Avaram Poo, Rose Powder, and Kasturi Manjal, confirmed through standard biochemical and Gram-staining techniques, and assessed for antibiotic resistance. Resistant isolates were subjected to plasmid curing, and plasmid loss was analyzed by alkaline lysis and agarose gel electrophoresis, followed by post-curing antibiotic susceptibility testing. The key findings revealed that several isolates carried plasmids associated with resistance, and SDS- and heat-shock-based curing resulted in partial or complete loss of plasmids, restoring antibiotic sensitivity in treated strains. These results demonstrate that herbal cosmetic powders can serve as overlooked reservoirs of plasmid-mediated antibiotic-resistant E. coli, and effective plasmid curing highlights the direct link between plasmid presence and drug resistance. The study emphasizes the need for stricter microbial quality control in herbal cosmetic manufacturing and provides baseline evidence that can guide regulatory policies and future antimicrobial resistance research.