Hydroxyethoxy phenyl butanone, a new cosmetic preservative, does not cause bacterial cross-resistance to antimicrobials

Introduction. Biocide-induced cross-resistance to antimicrobials in bacteria has been described and is a concern for regulators. We have recently reported on a new protocol to predict the propensity of biocide to induce phenotypic resistance in bacteria. Aim. To measure bacterial propensity to develop antimicrobial resistance following exposure to a new cosmetic preservative developed by L'Oreal R and I. Methodology. Well-established antimicrobials including triclosan (TRI) and benzalkonium chloride (BZC) and a new molecule hydroxyethoxy phenyl butanone (HEPB) were investigated for their antimicrobial efficacy, effect on bacterial growth, and their potential to induce resistance to chemotherapeutic antibiotics using a new predictive protocol. Results. The use of this predictive protocol with Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa showed that TRI and BZC significantly affected bacterial growth, MICs and minimum bactericidal concentrations (MBCs). There was no change in antibiotic susceptibility profile following exposure to BZC, but E. coli became intermediate resistant to tobramycin following treatment with TRI (0.00002 % w/v). HEPB did not change the antimicrobial susceptibility profile in P. aeruginosa and S. aureus but E. coli became susceptible to gentamicin. TRI exposure resulted in bacterial susceptibility profile alteration consistent with the literature and confirmed the use of TRI as a positive control in such a test. Conclusion. Data produced on the propensity of a molecule to induce bacterial resistance is useful and appropriate when launching a new preservative.