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 forskalin 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 forskalin’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, forskalin 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 forskalin 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 forskalin.

In the latest experiments, the researchers injected forskalin 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 forskalin 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.

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

Contact: Richard Merritt
Duke University Medical Center