The World Health Organization has identified antimicrobial resistance as a worldwide concern because most clinical antibiotics are no longer effective against certain pathogenic bacteria. Antibiotics work by targeting specific parts of a bacteria cell, such as the cell wall or its DNA. Bacteria can become resistant to antibiotics in a number of ways, including by developing efflux pumps — proteins that are located on the surface of the bacteria cell. When an antibiotic enters the cell, the efflux pump pumps it out of the cell before it can reach its target so that the antibiotic is never able to kill the bacteria. However, in a new study published in Nature Communications, scientists say they've found a new class of molecules that inhibit the efflux pump and make the antibiotic effective again. The researchers include Katie M. Kuo, Ph.D. scholar in the School of Chemistry and Biochemistry, and James C. Gumbart, professor in the School of Chemistry and Biochemistry with an adjunct appointment in the School of Physics.