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Science Service, Inc.
Viruses That Slay Bacteria
Draw New Interest
Travis, J. - Science News
June 3, 2000
For people with a damaged liver or too much iron in their blood,
enjoying raw oysters from the Gulf of Mexico is a deadly gamble.
Most of the oysters harbor Vibrio vulnificus, a bacterium
responsible for almost all seafood-related deaths in the United
States. Healthy people shrug off the microbe, but susceptible
folks who get a full-blown infection have more than a 50 percent
chance of dying. "You can be dead within 24 hours," says Paul A.
Gulig of the University of Florida College of Medicine in
Gainesville. Seeking a treatment that works faster than
antibiotics do, he and his colleagues recently isolated a
bacteria-killing virus, or bacteriophage, that targets V.
vulnificus and can prevent the deaths of mice infected with it.
Gulig's report was one of a handful on bacteriophage therapy
presented last week at the American Society for Microbiology (ASM)
meeting in Los Angeles. Other scientists described phages that
attack bacteria that cause anthrax, wound and burn infections,
and meat and poultry contamination.
Although U.S. physicians today don't embrace the strategy,
phage therapy dates back almost a century (SN: 6/1/96, p. 350).
The viruses infect, reproduce within, and eventually burst
bacteria. Since phages reproduce only as long as they have
target bacteria to infect, Elizabeth M. Kutter of Evergreen
State College in Olympia, Wash., calls the viruses
"self-replicating, self-limiting antibiotics."
In the V. vulnificus work, Gulig and his colleagues sampled
muck from oyster beds and isolated phages that destroy the
bacterium. They simultaneously infected mice with V. vulnificus
and enriched the rodents' blood with iron, which helps the
bacterium thrive. When given phages at the time of infection,
five of eight mice remained healthy. Without such treatment, all
mice succumbed within 18 hours.
Gulig cautions that his team has just begun to examine phage
therapy for V. vulnificus. The scientists plan to test a
cocktail of phages and to find out whether phages can help
rodents when treatment comes a few hours after infection.
Like Gulig, Michael H. Walter of the University of Northern
Iowa in Cedar Falls has turned to phages to defeat a deadly
bacterium. His enemy is Bacillus anthracis, the germ responsible
for anthrax.
Since the anthrax bacterium is dangerous to handle, Walter's
group has begun characterizing phages that infect a harmless
relative, Bacillus cereus. Such viruses may prove useful in
anthrax therapy, says Walter, or in destroying stockpiles of B.
anthracis captured from terrorists or rogue countries.
As bacteria increasingly develop antibiotic resistance,
several U.S. companies have also taken an interest in phage
therapy. One, the Baltimore firm Intralytix, works closely with
the Eliava Institute of Bacteriophage, Microbiology, and
Virology in Tbilisi, Georgia, which has developed phages for
medical use since 1934. Physicians in the former Soviet Union
regularly turn to phages.
At the ASM meeting, Intralytix cofounder and Georgian
scientist Alexander Sulakvelidze described his firm's progress
in identifying phages that destroy the Salmonella bacteria that
commonly infect meat, poultry, and eggs. One phage alone kills
90 percent of common Salmonella strains, and a cocktail of
phages eliminates 95 percent, he says.
Intralytix scientists bought chicken in groceries and seeded
it with Salmonella. Spraying the poultry with phages
dramatically reduced contamination, the researchers report.
Sulakvelidze predicts that the poultry industry will begin
testing this disinfection strategy in their processing plants
within a year.
Moreover, Intralytix plans to bring to market a U.S. version
of a bacteriophage-impregnated, biodegradable polymer originally
created by Georgian scientists. Intended to prevent infections
in burns and wounds, the skinlike dressing has passed clinical
testing in Georgia. Kutter calls it "the most exciting new
phage-therapy product in recent years."
Intralytix and several other firms are also studying whether
phages can help people infected with strains of Enterococcus and
Staphylococcus that are resistant to all antibiotics, including
vancomycin, currently the drug of last resort. "There's nothing
else we can use to treat these patients," says Sulakvelidze.
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