Proposal for assessment of the antimicrobial efficacy of undiluted medical honey: Using a standardized phase 2/step 2 in vitro stainless steel disc carrier test model

Abstract

Abstract PurposeThe antimicrobial efficacy of medical honeys used for professional wound care was published previously. So far, all in vitro antimicrobial tests performed have been conducted using non-standardized methods and used diluted medical honey. A standardized, reproducible phase 2/step 2 in vitro disc carrier model is proposed allowing testing the antimicrobial efficacy of undiluted medical honey. MethodsUsing a standardized disc carrier model, the log10 Reduction Factor (RF) of undiluted medical honey was determined for MSSA, MRSA, VRE, Pseudomonas aeruginosa, and Candida albicans, with and without protein challenge. ResultsAn antimicrobial efficacy was observed after 1h. Without organic challenge, log10RF >5 within 24h was achieved for all tested microorganisms, except for Staphylococcus aureus (log10RF: 4.8/24h). Challenged with 10% bovine serum albumin, a similar pattern was observed at 24h. The most susceptible organism was C. albicans (log10RF of >3/5min). Over an exposure time of 48h, the tested medical honey's antimicrobial activity under protein challenge achieved log10RFs >6 for C. albicans and >7log10 for all tested bacteria. ConclusionsIt was demonstrated that the proposed standardized phase 2/step 2 in vitro stainless steel disc carrier test model is applicable for testing the antimicrobial activity of highly viscous and undiluted compounds such as medical honey. Undiluted medical honey exhibits a strong antimicrobial efficacy even under protein challenge after 1h, which increases to >6log10 for C. albicans, and >7log10 for Gr+ and Gr− bacteria.