By Will Dunham

WASHINGTON, Mar 20 (Reuters) - Scientists said on Monday they have discovered the medical equivalent of a "smart bomb" to kill the type of bacteria responsible for strep throat and other infections.

Researchers at Rockefeller University said they found a way to kill streptococci bacteria on contact using enzymes produced by tiny viruses, or bacteriophages, that infect bacteria. The technique may not cause the bacteria to evolve resistant strains as antibiotics do and could have applications for many other bacterial diseases.

"It's what we call targeted killing, in which we kill only the disease bacteria without disturbing the normal bacteria needed for health, unlike antibiotics, which kill everything," Vincent Fischetti, who led the research, said in a statement.

The research was published in the Proceedings of the National Academy of Sciences.

The enzymes kill targeted bacteria by punching holes in the cell walls, Fischetti said. "We can take 10 million organisms in a test tube, add a very small bit of enzyme, and five seconds later, they are all dead. Nothing other than strong chemical agents can kill bacteria this quickly."

In addition to being incredibly potent, the enzymes also are highly specific, researchers said, searching out a target just as a "smart bomb" finds military target on a battlefield.

Strep throat is one of many diseases caused by Group A streptococci. Although not life-threatening in itself, strep throat can develop into rheumatic fever, which permanently damages the heart. Some 30% of children develop strep throat infections annually.

The method has potential applications beyond strep throat, by controlling common ear infections, staph infections and flesh-eating disease. The US military has expressed interest in the findings because of a need to control strep infections in the ranks, researchers said.

Fischetti said every type of bacteria has a corresponding bacteriophage that infects it. The enzyme corresponding to the streptococcus bacteria, when purified, will kill only certain streptococci when applied to the microbes on mucous membranes, leaving harmless bacteria alone, researchers said.

Related MEDLINEplus Pages:

• Mouth and Throat Disorders
• Streptococcal Infections