Efflux Pumps of Mycobacterium tuberculosis Play a Significant Role in Antituberculosis Activity of Potential Drug Candidates

Abstract

ABSTRACTActive efflux of drugs mediated by efflux pumps that confer drug resistance is one of the mechanisms developed by bacteria to counter the adverse effects of antibiotics and chemicals. To understand these efflux mechanisms inMycobacterium tuberculosis, we generated knockout (KO) mutants of four efflux pumps of the pathogen belonging to different classes. We measured the MICs and kill values of two different compound classes on the wild type (WT) and the efflux pump (EP) KO mutants in the presence and absence of the efflux inhibitors verapamil andl-phenylalanyl-l-arginyl-β-naphthylamide (PAβN). Among the pumps studied, the efflux pumps belonging to the ABC (ATP-binding cassette) class, encoded byRv1218c, and the SMR (small multidrug resistance) class, encoded byRv3065, appear to play important roles in mediating the efflux of different chemical classes and antibiotics. Efflux pumps encoded byRv0849andRv1258calso mediate the efflux of these compounds, but to a lesser extent. Increased killing is observed in WTM. tuberculosiscells by these compounds in the presence of either verapamil or PAβN. The efflux pump KO mutants were more susceptible to these compounds in the presence of efflux inhibitors. We have shown that these four efflux pumps ofM. tuberculosisplay a vital role in mediating efflux of different chemical scaffolds. Inhibitors of one or several of these efflux pumps could have a significant impact in the treatment of tuberculosis. The identification and characterization ofRv0849, a new efflux pump belonging to the MFS (major facilitator superfamily) class, are reported.