Lab researchers

• Human trials slated for 1999
• Not the same strain as in food
• Related sites and stories

December 29, 1998
Web posted at: 6:57 p.m. EST (2357 GMT)

(CNN) -- A dreaded cause of food poisoning, salmonella might actually have a good use, according to researchers at Yale University. A new report shows the bacteria appears to fight cancer.

"When we administer this to mice that have tumors, there is a greater than 90 percent suppression of tumor growth," said David Bermudes of Vion Pharmaceuticals, which teamed up with Yale to conduct the research.

Scientists infected the mice with human cancer tumors. Then they injected genetically engineered salmonella into the bloodstream of the animals. The salmonella bacteria sought out the tumors, multiplied inside them and slowed the growth of the cancer.

"We can now significantly prolong the life of mice with melanoma by injecting them with our attenuated bacteria," Dr. John Paweleck says on the Yale Cancer Center Web site.

Dawn Willis of the American Cancer Society was enthusiastic about the research.

"The idea of using a potential pathogen to invade a cancer cell and kill it without harming normal cells is a unique idea," she said.

Human trials slated for 1999

Scientists aren't exactly sure why salmonella seems to work. Yet they plan on approaching the Federal Drug Administration to start human trials sometime in 1999.

But giving salmonella to humans is a risky proposition. What if the cancer gets better, but the patients die of food poisoning?

Salmonella found in uncooked meats is not the strain used in the cancer research

That's why the Yale and Vion researchers are so impressed with this genetically altered salmonella. The lab animals in the study did not get sick.

"What we've been able to do is to remove toxic consequences of salmonella yet retain their beneficial properties of specifically targeting tumors and suppressing tumor growth," Bermudes said.

Unaltered or "wild" salmonella kills all types of cells; the re-engineered strain targets only tumor cells. While as few as 10 natural salmonella bacteria are enough to kill a mouse, mice injected with 10 million cells of the mutant strain showed no signs of infection.

Not the same strain as in food

Despite the discovery, cancer experts urge patients to remember that salmonella found in food won't fight cancer.

"This is a very special bacteria. It's not the one they are going to get from raw chicken," Willis said. "It's a laboratory strain that's been very carefully genetically engineered not to cause them any harm."

Willis also reminds patients that what works in mice could fail in humans. And it could take 15 years to complete human studies.

CNN's Elizabeth Cohen contributed to this report.