Until now, scientists thought that disease-causing bacteria left on the toy was the culprit in transferring the disease from the first child to the second. New research at The Rockefeller University shows that the culprit sometimes might not be the bacteria but a virus that infects and destroys the bacteria. Called a bacteriophage, this "bacteria-eating" virus causes disease by transferring toxins and other disease-causing genes between bacteria.
The findings, reported in the July issue of Infection and Immunity, show for the first time that bacteriophage, or phage -- previously thought not to be infectious to humans -- may be a new target for fighting certain bacteria that produce toxins.
"Controlling the phage may be as important as controlling the bacteria," says senior author Vincent A. Fischetti, Ph.D., professor and head of the Laboratory of Bacterial Pathogenesis and Immunology at Rockefeller.
"It's possible that phage present in the saliva of a child or another individual can cause the conversion of an existing non-toxigenic organism to a toxigenic one," adds Fischetti. "We always believed that phage were not infectious to humans, but in a sense, they are."
Scientists classify certain bacteria such as those causing scarlet fever, diphtheria and E. coli O157 (a source of food poisoning in contaminated meats) as toxigenic, meaning that these microbes produce toxins -- transported by phage -- that cause disease.
People can carry colonies of bacteria, such as strep, without being sick if the microbe doesn't carry a toxin-encoded phage. But, when a toxin-producing phage moves to a nonvirulent bacterium, it carries with it a toxin gene that is part of the phage genome, and transfers that gene to the new organism. This process, called lysogenic conversion,
Contact: Joseph Bonner