Human Diet Gives Deadly Bacteria a Target

University of Adelaide scientists are part of an international research team that has uncovered the first example of a bacterium causing disease in humans by targeting a molecule that is incorporated into our bodies from our diet. The discovery was published today in the journal Nature.

Microbiologists Dr. Adrienne Paton and professor James Paton, and their collaborators, have shown that a potent bacterial toxin, Subtilase cytotoxin, specifically targets human cells that express a sugar called Neu5Gc on their surface.

"Remarkably, humans cannot make Neu5Gc, and so we should all be resistant to the toxin," Paton says. "However, consuming foods that have high levels of Neu5Gc, such as red meat and dairy products, leads to uptake of the sugar by human cells and this makes them susceptible to attack by the toxin."

Subtilase cytotoxin is produced by E. coli bacteria that cause bloody diarrhea and hemolytic uraemic syndrome (HUS) in humans. Paton says in HUS, toxin-induced damage to the delicate cells lining the blood vessels causes clots, damage to red blood cells and kidney failure. Humans usually become infected with the potentially deadly E. coli after eating contaminated food, as occurred during Adelaide's Garibaldi outbreak in 1995.

"Red meat and dairy products, the richest dietary sources of Neu5Gc, are also the foods that are most commonly contaminated with the E. coli bacteria that produce the toxin," Paton says. "Through dietary choices, therefore, humans may expose themselves to an increased risk of infection with the E. coli bacteria and simultaneously sensitize themselves to the potentially lethal actions of the toxin it produces."

The international research team also included scientists from Monash University, the University of California (Davis and San Diego) and Emory University.

"This research emphasizes the need for people to eat only well-cooked red meat (particularly for hamburgers), or pasteurized dairy products, as these processes destroy contaminating bacteria," Paton says.

The research was funded by Australia's National Health and Medical Research Council and the National Institutes of Health.