Silver Makes Antibiotics Thousands of Times More Effective

Brian Owens Bacteria have a weakness: silver. The precious metal has been used to fight infection for thousands of years, but how it works has been a mystery. Now, a team led by James Collins, a biomedical engineer at Boston University, has described how silver can disrupt bacteria, and shown that the ancient treatment could help to deal with the thoroughly modern scourge of antibiotic resistance. “Resistance is growing, while the number of new antibiotics in development is dropping,” says Collins. “We wanted to find a way to make what we have work better.” Collins found that silver attacks bacterial cells in two main ways: it makes the cell membrane more permeable, and it interferes with the cell’s metabolism, leading to the overproduction of reactive, and often toxic, oxygen compounds. Both mechanisms could be harnessed to make today’s antibiotics more effective against resistant bacteria, Collins says. Many antibiotics are thought to kill their targets by producing reactive oxygen compounds, and Collins showed that when boosted with a small amount of silver these drugs could kill between 10 and 1,000 times as many bacteria. The increased membrane permeability also allows more antibiotics to enter the bacterial cells, which may overwhelm the resistance mechanisms that rely on shuttling the drug back out. That disruption to the cell membrane also increased the effectiveness of vancomycin, a large-molecule antibiotic, on Gram-negative bacteria—which have a protective outer coating. Gram-negative bacterial cells can often be impenetrable to antibiotics made of larger molecules. “It’s not so much a silver bullet; more a silver spoon to help the Gram-negative bacteria take their medicine,” says Collins. Click to Read Full Article