Treating bacteria
with a silver-containing compound boosted the efficacy of a broad range of
widely used antibiotics and helped them stop otherwise lethal infections in
mice. It helped make an antibiotic-resistant strain of bacteria sensitive to
antibiotics again. And it expanded the power of an antibiotic called vancomycin
that is usually only effective in killing pathogens called Gram-positive
bacteria, such as Staph and Strep. Silver allowed vancomycin for the first time
to penetrate and kill Gram-negative bacteria, a group that includes microbes
that can cause food poisoning and dangerous hospital-acquired infections.
silver compounds
cause bacteria to produce more reactive oxygen species -- chemically reactive
molecules that damage the bacterial cell's DNA and enzymes, as well as the
membrane that encloses the cell. Silver also made the bacteria's cell membrane
leakier.
Although silver was
used alone as a therapy in the past, the scientists suspected that both changes
might make cells more vulnerable to conventional antibiotics -- and they did. A
small amount of silver made E. coli bacteria
between 10 and 1000 times more sensitive to three commonly used antibiotics:
gentamycin, ofloxacin, and ampicillin.
And it allowed
vancomycin to save the lives of 90 percent of mice with life-threatening cases
of peritonitis -- inflammation caused by infections of the abdominal space
surrounding the internal organs. Without silver, only 10 percent of the mice
survived. [!!!!!!!!!!!]
The scientists also
did a series of toxicity studies, showing that the doses of silver needed to
help antibiotics kill bacteria were far below what could harm the mice. Nor did
they harm cultured human cells, suggesting that oral and injectable silver
could be safe for humans as well.
