Cholecalciferol, Ergosterol, and Cholesterol Enhance the Antibiotic Activity of Drugs.

Unlabelled: Background: This is the first report demonstrating the antibiotic-modifying activity of cholecalciferol.

Aim: In this study, cholecalciferol was evaluated against multiresistant strains of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli.

Methods: The antibacterial and modulatory effects of cholecalciferol, ergosterol, and cholesterol (8-512 μg/mL) were evaluated by microdilution assay against multiresistant bacterial strains.

Menadione (vitamin K) enhances the antibiotic activity of drugs by cell membrane permeabilization mechanism.

Menadione, vitamin K3, belongs to the class of lipid-soluble vitamins and lipophilic substances as menadione cause disturbances in the bacterial membrane, resulting in damage to the fundamental elements for the integrity of the membrane, thus allowing increased permeability. Accordingly, the aim of this study was to evaluate in vitro the antibiotic-modifying activity of menadione in multiresistant strains of , and , with a gradual increase in its subinhibitory concentration. In addition, menadione was compared with cholesterol and ergosterol for similarity in mechanism of drug modulatory action.