Estradiol Modulates the Sensitivity to Vancomycin of Lactobacillus paracasei and Staphylococcus aureus Biofilms-Constituents of Human Skin and Vaginal Microbiota.

We investigated the effects of vancomycin, estradiol, ethanol, and their combinations on the growth of mono- and binary-species biofilms of Lactobacillus paracasei and Staphylococcus aureus. It was found that vancomycin at a subinhibitory concentration of 0.001 µg/mL, estradiol, and ethanol acted antagonistically in all cases. This effect was observed across all strains studied. Furthermore, the effects of the active compounds were evident at population, cellular and molecular levels, and were reflected in changes to the count of colony-forming units (CFUs), gene expression, and the physiological and biochemical characteristics of cells (e.g., lipid composition of membranes and the extracellular matrix). Therefore, at subinhibitory concentrations of vancomycin in the medium, estradiol can modulate the antibiotic's effect on biofilms, thereby regulating deeply microbial communities.