LOS ANGELES -- Thousands of years before the discovery of microbes or the invention of antibiotics, silver was used to protect wounds from infection and to preserve food and water.
The alluring metal -- which was fashioned into a multitude of curative coins, sutures, foils, cups and solutions -- all but vanished from medical use once physicians began using anti-bacterial drug agents to fight sickness in the 1940s.
But now, as bacteria grow increasingly resistant to these medications and new pathogens invade hospitals, some doctors are turning once again to the lustrous element Hippocrates prescribed for patients in ancient Greece.
In a study published in Science Translational Medicine, researchers found by adding trace amounts of silver to common antibiotics, the medications became up to 1,000 times more effective in fighting infections in mice.
Also, study authors said they were surprised and excited to find the silver-antibiotic combo was able to "re-sensitize" bacteria that had developed a resistance to the drugs. It even extended the effectiveness of the commonly used antibiotic vancomycin to a class of bacteria that was previously immune to its effects.
"We went from basically no killing to substantial killing," said senior author James Collins, a professor of microbiology at Boston University.
The study is one of the first comprehensive examinations of the ways silver affects bacteria that are known as Gram-negative. These bacteria are equipped with an extra protective membrane that prevents antibiotic drug molecules from penetrating and killing them.
In a series of experiments, Collins and colleagues from BU and Harvard University examined the effects of a simple solution of silver nitrate salt on Gram-negative bacteria like Escherichia coli.
What they found was even small amounts of silver ran roughshod over some of the toughest bacteria around.
"It did two things," Collins said. The positively charged silver ions degraded the bacteria's protective layer, giving the antibiotics easier access to the pathogens' innards. It also messed with the bugs' metabolism and their ability to manage their iron levels.
Silver has been used variously to treat skin ulcers, compound fractures and even bad breath.
In his History of the Medical Use of Silver, Dr. J. Wesley Alexander wrote North American pioneers routinely dropped silver coins into vessels of drinking water during long journeys to ward off infection. In addition, privileged families benefited from using silver eating utensils that often caused "a bluish-gray discoloration of the skin, thus becoming known as 'blue bloods.'"
-- Los Angeles Times