Combating Multidrug Resistance in Bacteria by Inhibition of Efflux Pumps

Since the discovery of antibiotics, many otherwise deadly infections have been rendered mere inconveniences. Unfortunately, as antibiotic use has increased over the course of the last century, bacteria have been given more and more opportunities to adapt. Antibiotic resistance allows bacteria to survive in the presence of antibiotics, thus continuing the infection and rendering treatment useless. Bacteria have developed many different mechanisms that confer resistance, among these is overexpression of E. coli’s AcrAB-TolC efflux pump in the cell membrane. The efflux pump, necessary for expulsion of wastes and toxins from the intracellular space, is present in all E. coli cells, however it is present in much larger numbers in resistant cells. This increase in expression allows E. coli to pump out toxins at a much higher rate, thus preventing the antibiotic from accumulating within the cell to reach a therapeutic dosage. An inhibitor of AcrAB-TolC would decrease the rate of efflux and allow accumulation of antibiotics. In order to discover inhibitors, edible plants were obtained and extracts were created and tested in an ethidium bromide-based efflux assay. Green tea extract was found to have significant inhibitory activity. HPLC was used to separate the components of the green tea extract to aid in identification of the active compound. NMR analysis of the active fraction was consistent with a type of aromatic molecule known as a catechin