May 7, 2003
Easy to attain and inexpensive to produce, foodborne pathogens have been called the poor man's atom bomb.
"Species of clostridia have already been weaponized," said Hans Blaschek, a food microbiologist at the University of Illinois, who was asked to develop a rapid detection system for airborne species of Clostridium during the Gulf War. "The Army believed that the Iraqis intended to use Scud missiles to deliver the aerosolized pathogen, which would cause a gas gangrene to develop in the open wounds of soldiers," he said.
Blaschek also said that recovered documents indicate that al Qaida had targeted the U.S. water supply for contamination with biological and chemical agents.
Researchers in the Micro and Nanotechnology Laboratory at the U of I are currently developing sensors that will detect the presence of chemical and biological toxins by soldiers in combat and in domestic situations.
Blaschek works with Clostridium perfringens, Shigella boydii, and E. coli, National Institute of Allergy and Infectious Diseases (NIAID) category B priority pathogens. Scott Martin is a U of I expert on Listeria monocytogenes, also a category B priority pathogen. All of these bacteria can cause food poisoning when they are ingested in food.
Neither Blaschek nor Martin believes these pathogens are especially good candidates for domestic bioterrorism on a large scale. "It takes a while for an infection to develop, and not everyone who comes in contact with the organism develops it," Martin said. In most people, these pathogens cause mild flu-like symptoms. Serious illness occurs mainly in the very old, the very young, and people with weakened immune systems.
But Martin and Blaschek believe these organisms are dangerous enough when contamination is unintentional.
"Listeria is clearly the most virulent foodborne pathogen, with a fatality rate of 33 percent in people who develop complications," said Martin.
"Listeria is especially dangerous because it can grow at refrigeration temperatures," he said. "Poultry that has been cooled, sliced, and stored may have a shelf life of 60 to 90 days. An almost undetectable level of contamination can grow at refrigeration temperatures in that time and cause infections."
Listeria is associated with raw foods, such as uncooked meat and vegetables, and foods that have become contaminated after processing, such as soft cheeses and sliced meat and poultry products sold at deli counters.
It is a particular threat to pregnant women, whose infection rate is 17 times higher than the general public. Although a woman may not show symptoms of illness, the organism can penetrate the uterus, infect the baby, and cause spontaneous abortion. In Europe and Australia, pregnant women are advised to avoid products associated with listeria, Martin said.
Blaschek is working with two foodborne pathogens that are behaving in unexpected ways.
Once a minor problem in the U.S., shigella is turning up more and more frequently with the globalization of the world food supply. "The organism is piggybacking onto produce in countries that use animal waste fertilizers and have less stringent food-processing procedures than we do," Blaschek said.
Most produce receives very little processing, and shigella is especially difficult to remove because it attaches itself with biofilms that grow and multiply, adhering so tightly that it's difficult to scrub them off. Blaschek is studying the organism's attachment mechanism.
Shigella may soon pass salmonella in the number of reported cases of foodborne illness in this country, Blaschek said.
He is also investigating the transmission of E. coli 0157:H7 in apple juice and apple cider. "Thirty years ago, we were taught that these pathogens would not survive, and certainly wouldn't grow, in high-acid environments like fruit juice. The genetically encoded resistance of the organism has obviously changed," Blaschek said.
"The important thing to remember," said Martin, "is that these pathogens are killed if food is reheated to 165°F. Consumers should be aware of these organisms, but they should also know that they're not powerless against them."