Tracking a Dangerous Toxin
A trip to the petting zoo turns deadly.
In 1989, while visiting a local petting zoo with her three-year-old son, LAS microbiologist Brenda Wilson hand-fed pieces of grass to a goat. It was a good deed that nearly killed her. The goat infected her with a bacterium called Pasteurella multocida, and Wilson battled the infection for three weeks in the hospital, where she lost hearing in one ear and had her tonsils removed. After recovering, Wilson recalls, "I got interested and asked, What did this to me?"
The answer, she learned, was the microbe's toxin. Like anthrax and several other disease-causing bacteria, Pasteurella secretes a toxin that damages human cells, continuing its onslaught even after antibiotics wipe out the infecting microbes. Vaccines, if they're available, can prevent such infections, but once toxins are released and affect cells, "we have no antidotes," Wilson says.
To help find an antidote to Pasteurella's toxin, which can cause bone and fat loss, skin tumors, and kidney damage, Wilson and her colleagues first tagged the toxin with a jellyfish protein that fluoresces green, then watched under a microscope as the glowing toxin infiltrated human cells. It turned out that the toxin uses a different part of its surface as a pass key of sorts to enter different types of cells, which could explain how it can damage a wide variety of tissues. The tracking method could also enable researchers to test potential drugs that block bacterial toxins, including anthrax toxin, from invading and damaging cells.