Bile compounds are effective inducer of efflux pump-mediated antimicrobial resistance among Gram-negative bacteria

Bile is a liquid or solution containing various substances which have a varied antimicrobial effect, especially on Gram-positive bacteria. When bacteria encounter low concentrations of bile or bile salts, the transcription of several genes' changes. Most of these genes play a role in neutralizing the toxic effects of bile. These alternations may impact structural proteins or the secretion of specific enzymes, whose expression is linked to changes in bacterial morphology and growth rate. Consequently, when exposed to bile, bacteria induce a particular response that significantly influences their interaction with host cells and surfaces. Understanding the impact of different substances, including bile, on the microbial physiology is essential for identifying the pathogenesis and resistance mechanisms. Resistance-Nodulation-Division (RND) type efflux pumps play an important role in providing resistance of Gram-negative bacteria to antibiotics. The expression of efflux pumps can be altered by bile, potentially resulting in the development of resistance to other antimicrobial compounds. This review discusses the impacts of bile and bile salts on the expression levels of efflux pumps in Gram-negative bacteria, as well as their effect on antibiotic resistance.