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DURHAM, N.C. -- A common herbal extract available in health
food stores can greatly reduce urinary tract infections and
could potentially enhance the ability of antibiotics to kill
the bacteria that cause 90 percent of infections in the
bladder.

Researchers at Duke University Medical Center, in a series
of experiments in mice, believe they have also discovered why
many urinary tract infections in the bladder return even after
treatment with antibiotics. They found that some bacteria hide
in cells lining the bladder, where they cannot be reached by
antibiotics. But they also found that forskolin, an extract
from the Indian coleus plant, flushes out hiding colonies of
bacteria, making them susceptible to antibiotic treatment.

About 90 percent of urinary tract infections in the bladder
are caused by E. coli bacteria. These infections afflict women
four times as often as men, and in a large number of cases, the
infection returns within weeks of antibiotic treatment.

The research was led by Duke microbiologist Soman Abraham,
Ph.D., who published the results online April 8, 2007, in the
journal Nature Medicine. The research was supported by the
National Institutes of Health.

The lining of the bladder is a highly impenetrable surface,
Abraham said. Special pouchlike structures within the lining
enable the bladder to stretch as it fills with urine. However,
when infected, the pouches can create tiny niches that some
opportunistic E. coli can slip into and hide.

"After customary antibiotic treatment, the vast majority of
the bacteria are either killed by the antibiotics or eliminated
during urination," Abraham said. "However, there are small
numbers of bacteria that survive antibiotic treatment because
they sneak into the lining of the bladder, waiting for the
opportunity, after antibiotic treatment, to come out and start
multiplying again."

The researchers found that forskolin has the ability to
force the bacteria out of their niches and into the urine,
where they can be killed by antibiotics.

Abraham said that forskolin's action makes intuitive sense,
since the herb is known to rev up certain cellular activity.
This heightened activity in the bladder causes the specialized
pouches to "flush out" their contents -- in this case, the
hiding E. coli.

"This herb has been used in Asia for centuries for a wide
variety of ailments," Abraham said. "However, one of its
constant uses has been for treating painful urination."

Today, forskolin is added to bodybuilding products and
marketed for its ability to increase lean body and bone mass,
as well as to increase testosterone levels. The herb also has
been claimed to be an effective weight-loss aid. Herbal
extracts such as forskolin are not tested nor regulated by the
Food and Drug Administration. Abraham recommends that anyone
with a urinary tract infection should contact their physician
before trying forskolin.

In the latest experiments, the researchers injected
forskolin directly into the bladder or administered it
intravenously. The herb appeared to expel more than 75 percent
of the hiding E. coli. The researchers next will determine
whether or not the herb is effective when mice receive it
orally, since that is how it would be used in humans. The
experiments also will combine the use of forskolin and
antibiotics.

"This type of treatment strategy may prove to be beneficial
for patients with recurrent urinary tract infections," Abraham
said. "Ideally, use of this herb would expel the bacteria,
where it would then be hit with antibiotics. With the reservoir
of hiding bacteria cleared out, the infection should not
recur."

Abraham said that a new and effective approach for treating
urinary tract infections is needed, because constant antibiotic
use has many drawbacks, including high expense, possible liver
and kidney damage and the potential for creating strains of
antibiotic-resistant bacteria.

Other Duke members of the team were Brian Bishop, Mather
Duncan, Jeongmin Song, Guojie Li and David Zaas.