Parliamentary Yearbook examines new research which suggests that adding silver
to antibiotics makes them one thousand times more effective at fighting infections. It is hoped that the findings could help in
the fight against antibiotic resistance.
Silver has been used as an
antimicrobial for centuries. Despite this widespread use, the exact mechanism
of its action has remained unclear. New research by a team of American
scientists has been published in the journal Translational Medicine which
identifies exactly how silver fights bacteria in a number of ways. The research suggests that adding silver to
existing anitbiotics could help strengthen the antibiotic arsenal for fighting
bacterial infections.
Silver
has been used to fight infections for thousands of years. Hippocrates first described its antimicrobial
properties in 400 b.c.; noting its special ability to preserve food and water.
Today silver is routinely used to treat and prevent infections and can be found
in wound dressings and catheters but the source of this precious metal’s
antibacterial properties has remained a mystery. In this latest research, James Collins, of the
Wyss Institute for Biologically Inspired Engineering at Harvard University and
colleagues from Boston University, describe a number of ways in which silver
fights bacteria.
The
study is important because it investigates the effects of silver on E.coli, a
Gram-negative bacterium. The most difficult types of infections to are those
that involve Gram-negative bacteria, like E.coli and Salmonella. These bacterial strains have an almost
impenetrable cell wall that shields them from antibiotics. They are resistant to multiple drugs and are
increasingly resistant to most available antibiotics. Gram-negative bacteria have built-in
abilities to find new ways to be resistant and can pass along genetic materials
that allow other bacteria to become drug-resistant as well.
The
research team conducted a series of experiments using E.coli in petri dishes
and in live mice suffering from urinary tract infections. The study aimed to investigate exactly how
silver kills Gram-negative bacteria.
The
findings show that silver mounts a multi-targeted attack on the bacteria which
breaks down their cells walls and increases their production of reactive oxygen
species (ROS), chemically reactive molecules containing oxygen. An increase in ROS molecules, caused by traditional
antibiotics or silver automatically triggers bacterial cell death.
The
researchers subsequently investigated the effects of combining silver with a
range of antibiotics. They found that the silver acted as a sort of Trojan
horse. It helped to deliver the
treatment beyond the cells’ walls which allowed the antibiotic to maximally
damage the bacterial cells.
The
findings were remarkable. They showed
that antibiotics, when combined with silver, were 10 to 1,000 times more
effective at fighting infections than when antibiotics alone were used. Even at
small doses, silver made the E.coli up to one thousand times more sensitive to
gentamycin, ofloxacin and ampicillin; three widely used antibiotics.
In
further tests with mice, they found that a E.coli urinary tract infection that
was resistant to tetracycline finally succumbed when the antibiotic was
combined with silver. Similarly, they
found that, combined with silver, vancomyin saved the lives of 90% of mice with
life-threatening peritonitis. Treated with vancomycin alone, 90% of the mice
died.
The
doses of silver used used in the experiments were tested to ensure they were
not toxic. The team showed that levels
were too low to harm the mice. It was also confirmed that levels used did not
harm human cells.
The
researchers believe that silver may enable existing antibiotics to treat a
wider range of infections, including those to which microbes have become
resistant.
Commenting
on the research, Jim Collins said:
“We’re keen to explore how smart drug-delivery nanotechnologies being
developed at the Wyss could help deliver effective but nontoxic levels of
silver to sites of infection.”
Email: parliamentaryyearbook@blakemedia.org
