Efflux pump inhibitors

Antibiotics are compounds, which inhibit the growth of or destroy microorganisms, thus are used to treat and prevent infections. But for some reason, microorganisms in time develop resistance to antibiotics. One of the reasons for resistance to antibiotics is efflux pumps. By means of these pumps, microorganisms export antibiotics entered into the bacterial cell; therefore, they cannot inhibit the growth of or destroy bacteria. This situation decreases the activity spectrum of the antibiotic and increases the antibiotic resistance. Thus, microorganisms could develop multiple drug resistance against not only the antibiotic used, but also for many other antibiotics and rapidly spread to the environment. For this reason, antibiotic resistance has become a major problem all over the world, and new antibiotics and efflux pump inhibitor studies are continuing rapidly. The aim of this study is to observe the response of some Escherichia coli clinical isolate strains with multiple drug resistance and overexpressed efflux pumps against efflux pump inhibitors, in order to use these strains for further studies. Ethidium bromide (EtBr)-agar cartwheel method was firstly used to identify E. coli strains with overexpressed efflux pumps by transferring inoculum of all strains to EtBr containing agars, and overexpressed efflux pumps were determined by exposing agar plates to UV light. Verapamil, phenyl arginine beta naphthylamide (PAβN) and thioridazine hydrochloride were used as efflux pump inhibitors (EPIs), and the lowest concentration of EPIs those inhibit the growth of E. coli strains were determined by minimal inhibition concentration (MIC) test. Lastly, the responses of microorganisms against efflux pump inhibitors were determined with a microplate based assay, by using EPIs below their MIC values. According to the results of this study; effect of verapamil and thioridazine was observed to be more effective than PAβN. As a result 98.41% of the E. coli strains used in the study was found to be affected by verapamil, where 96.82% by thioridazine and only 38.09% was affected by PAβN inhibitor.

Bacterial drug resistance is one of the most common problems of last several decades and it continues to delay the treatment of bacterial infections. Efflux pumps, which are one of the factors causing this resistance, prevent the drug from being kept inside the cell. Thus, the drug released outside the cell by the bacteria, and it cannot exhibit its activity and lead to antibiotic resistance. Although there are some efflux pump inhibitors to block the activity of these pumps, the use of currently known inhibitors is not suitable for clinical purposes, because of toxicity problems due to their chemical structure. The aim of this study is to screen in vitro efflux pump inhibitor activities of some extracts, which may be suitable for clinical use instead of using toxic synthetic inhibitors, in several Escherichia coli strains presenting multiple drug resistance and overexpressed efflux pumps. For this purpose, potential efflux pump inhibitors were extracted by using two solvents having different polarities. The results presented that all these extracts contain potential efflux pump inhibitors, which could have possible uses for blocking efflux pumps during antibiotic treatment. This experiment is a preliminary study, and it is necessary to purify and determine the active compound(s) in order to reach more detailed results about their mechanisms and to try the compounds with the combination of antibiotics to prove their potential use. Since the possibility of the use of these compounds depend on their toxicity, determining whether they are toxic or not will be a key step to continue to further studies.

Causative agents of infectious disease that are multidrug resistant bacterial pathogens represent a serious public health concern due to the increasingly difficult nature of achieving efficacious clinical treatments. Of the various acquired and intrinsic antimicrobial agent resistance determinants, integral-membrane multidrug efflux pumps of the major facilitator superfamily constitute a major mechanism of bacterial resistance. The major facilitator superfamily (MFS) encompasses thousands of known related secondary active and passive solute transporters, including multidrug efflux pumps, from bacteria to humans. This review article addresses recent developments involving the targeting by various modulators of bacterial multidrug efflux pumps from the major facilitator superfamily. It is currently of tremendous interest to modulate bacterial multidrug efflux pumps in order to eventually restore the clinical efficacy of therapeutic agents against recalcitrant bacterial infections. Such MFS multidrug efflux pumps are good targets for modulation.