"This is an intriguing finding and a hopeful step against a very worrisome
pathogen," says NIAID Director Anthony S. Fauci, M.D. "Within the last two
years, S. aureus has become increasingly resistant to antibiotics. Most
troubling is the emergence of strains that are partially resistant to
vancomycin, our last line of defense against S. aureus. New treatments and,
ideally, an effective vaccine, are urgently needed."
Each year an estimated 500,000 patients in American hospitals contract staph
infections. S. aureus, the chief culprit, also is a common source of
community acquired infections, and causes illnesses that range from minor
skin infections and abscesses to life-threatening diseases such as severe
pneumonia, meningitis, bone and joint infections, and infections of the
heart and bloodstream.
Molecules isolated from bacteria grown in the laboratory have been one
source of new vaccine candidates. However, since bacterial growth under
laboratory conditions may not mimic an actual infection, scientists recently
have begun searching for bacterial products that are activated specifically
"Presumably, these products are critical for infection and disease
progression, and would therefore be logical targets for new therapeutics or
vaccines," explains Gerald B. Pier, Ph.D., who led the research team that
developed the new S. aureus vaccine.
The researchers found that although tissue from humans and mice infected
with S. aureus contained a staph polysaccharide molecule known as PNSG
(poly-N-succinyl Beta-1-6 glucosamine), few S. aureus strains produced PNSG
when cultivated in the laboratory.
Dr. Pier and his colleagues purified the elusive molecule and injected it
into rabbits. The rabbits produced large amounts of PNSG antibodies that
persisted for at least eight months. The researchers then injected the PNSG
antibodies into mice and exposed them to eight different strains of S.
aureus, including strains resistant to the antibiotic methicillin and
partially resistant to vancomycin. None of the animals developed an
"Our findings suggest that this vaccine has the potential to provide
immunity to the multi-drug resistant S. aureus 'superbug' that we have heard
alarming reports of in the last year or so," says Dr. Pier.
"I think this work has a very good chance of being a major advance," says
Stephen Heyse, M.D., medical bacteriology and antibacterial resistance
program officer at NIAID. "It looks like a great vaccine candidate for
Staphylococci, in general, both S. aureus and S. epidermidis."
Dr. Pier and his colleagues note that in addition to S. aureus, other
bacterial species classified as coagulase-negative staphylococci, or CoNS,
also produce PNSG.
"Together, S. aureus and CoNS account for 40 percent to 60 percent of
bacterial blood isolates from hospitalized patients," says Dr. Pier.
"Therefore, an additional potential advantage of a PNSG vaccine might be
protection against the spectrum of clinically important CoNS."
Dr. Pier adds that he and his colleagues hope to move the PNSG vaccine into
human trials soon, but predicts that such trials are one to two years away.
They currently are negotiating licensing rights for the vaccine.
Other Ongoing NIAID S. aureus Research
Press releases, fact sheets and other NIAID-related materials are available
on the NIAID Web site at http://www.niaid.nih.gov.