Silver Could Make Antibiotic-Resistant Bacteria Vulnerable

Silver could boost antibiotics' ability to kill bacteria, according to a new study from Harvard University.

The study shows that bacteria treated with small amounts of silver are more vulnerable to antibiotics than those that aren't exposed to any. The finding could help deal with rising levels of antibiotic resistance.

Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University found that treating bacteria with a silver-containing compound was effective in stopping an otherwise lethal infection in mice. Even the bacteria that were resistant towards an antibiotic became vulnerable to attack after being treated with silver.

The study also found that silver increased the efficiency of Vancomycin, an antibiotic that isn't known to kill gram positive bacteria. Silver compounds make E. coli 10 to1000 times more sensitive to common antibiotics such as gentamycin, ofloxacin, and ampicillin.

Interestingly, silver treated bacteria weren't able to produce a biofilm and didn't turn dormant. Usually it takes several rounds of antibiotics to kill bacteria that become dormant.

"The results suggest that silver could be incredibly valuable as an adjunct to existing antibiotic treatments," said Jim Collins, Ph.D.,  Core Faculty member at the Wyss Institute, according to a news release. 

Centers for Disease Control and Prevention (CDC) says that the threat of microbes getting resistant to a drug isn't only isolated to a particular country, but is a problem faced by the entire world. The U.S. for example faces some real danger from methicillin-resistant Staphylococcus aureus (MRSA). Recently, the agency announced the rise of nightmare bacteria- carbapenem-resistant Enterobacteriaceae, that have become resistant to the last-resort antibiotics called carbapenems.

In the present study, Ruben Morones-Ramirez, Ph.D., a postdoctoral fellow at the Wyss Institute looked at the effect of a silver-compound on strains of E. coli.

Treating bacteria with silver compounds produces reactive oxygen species (ROS) molecules which damage the bacterial cells' DNA and enzymes. Silver also damages the cell membrane and makes it leakier, he found.

Researchers even tested various doses of silver compounds that could kill the bacteria. They found that the amount of silver required to make bacteria more sensitive to antibiotics would not cause any harm to human tissues. Oral or injectable silver could be used in humans, they said.

The study is published in the journal Science Translational Medicine.