Molecular imaging spoils mystery of listeriosis

With the help of molecular imaging, Stanford University biochemist Jonathan Hardy, Ph.D., has added a new chapter to the mystery of listeriosis, a sometimes fatal bacterial infection linked to unpasteurized cheese.

As anyone in France knows, pasteurization ruins the flavor of the 500 varieties of cheese manufactured there. The government accepts as a matter of course that a few French people will die every year after eating cheese infected with Listeria, the bacterial cause of listeriosis. (The USDA requires pasteurization for this reason.)

The Pasteur Institute has studied the bacterium for more than 70 years without definitively identifying which organ serves as its central point of habitation. Using recombinant gene technology, Hardy and colleagues introduced the gene for firefly luciferase into the DNA of the bacterium to allow noninvasive tracking with bioluminescent optical imaging in mice. He reportedly had no trouble persuading the mice to eat the subject of his investigation.

Hardy found that Listeria does its deadly work from the gallbladder, whose toxic bile contents were thought to kill bacteria. He presented the study at the 2005 Society of Molecular Imaging meeting in Cologne, Germany.