Multidrug-resistance proteins and drug-efflux pumps have been characterizedin many organisms, and they represent a widely used mechanism of drugresistance. In a recent issue of Antimicrobial Agents and Chemotherapy (April2005), investigators report results from a study of efflux pumps in Helicobacterpylori. The genome of H pylori 26695 contains 27 translocases, among whichare HP1184, which is similar to other well-characterized multidrug-resistancetranslocases, and 4 other translocases (HP0605, HP0971, HP1327, andHP1489), which are similar to outer membrane TolC proteins. Investigators performedgene knockout experiments and assessed the bacteria now lackingthese proteins for susceptibility to antibiotic and toxic compounds. The HP0605knockout mutant demonstrated increased susceptibility to novobiocin and sodiumdeoxycholate, and a double knockout of HP0605 and HP0971 hadincreased susceptibility to metronidazole.