Use of a small-scale, portable test chamber for determining the bactericidal efficacy of aerosolized glycol formulations

This study aimed to understand the efficacy and mechanisms of action of an aerosolized glycol-ethanol formulations against bacteria. We validated a small-scale in-house test chamber to determine the microbicidal efficacy of four aerosolized formulations combining dipropylene glycol and ethanol against Staphylococcus aureus and Escherichia coli embedded in alginate. The aerosolized glycol/ethanol formulation decreased bacterial viability by 3 log(10) and was more efficacious than an ethanol only control formulation. Electron microscopic examination indicated extensive structural damage in both bacteria, and membrane damage was confirmed with potassium release in S. aureus and DNA release in E. coli. The development of a small test chamber facilitated the measurement of the microbicidal efficacy and experiments to understand the mechanism of action of an aerosolized microbicidal formulation. Significance and Impact of the Study There is an increased interest in developing effective microbicidal-aerosolized formulations. The development of a small in-house test chamber allowed the measurement of the microbicidal efficacy of an aerosolized glycol/ethanol formulation at a low cost. We showed that a glycol/ethanol aerosolized formulation caused extensive structural damage in Gram-negative and -positive bacteria resulting in a 3 log(10) reduction in viability.