BY ADELLE LARMOUR

E. coli 0157:H7 tends to occur naturally in cattle, but can also be found in other animals like sheep, goats, as well as humans. The bacteria are found in feces and can be transmitted from one person to another as a result of improper hand washing or other means.

It can also be transferred by an intermediary, such as food, which can cause the bacteria to multiply quickly, explained Dr. Garry Ferroni, professor of microbiology at the Northern Ontario School of Medicine. “There is a much greater chance that other people can be infected by it. That is how we get these epidemics. Food or water becomes contaminated.”

Ground beef is known to carry the organism if, at some point during the processing, the meat has come into contact with the animal’s feces. This strain thrives best in a moist environment at 37 degrees Celsius. However, it will live at temperatures between eight and 47 degrees Celsius. The bacteria can be killed by heat at a minimum temperature of 71 degrees Celsius (160 degrees Fahrenheit), one of the reasons to thoroughly cook ground beef. Also, the bacteria will not survive on surfaces where they may dry out in a matter of hours.

To acquire the 0157:H7 strain, a person would only have to ingest about 500 cells to get ill, Ferroni said.

“Under ideal conditions, this particular bacterium can double its size every 15 to 20 minutes,” he said, adding that its growth is exponential. “Food provides a growth medium for the bacteria so that maybe 10 cells are introduced in a particular foodstuff, but within 24 hours, you might have 10 million cells.”

North Americans have little immunity to this strain because it only emerged in the early ’80s.

E. coli 0157:H7 may have been non-pathogenic, but it acquired two enterotoxins found in the Shigella species bacterium, making it pathogenic.

“That means the number of pathogenic strains is potentially increasing because of this acquisition of new genetic material,” said Ferroni. “If other non-pathogenic strains acquire the genes of the pathogenic strains, they, in turn, become deadly. This is what we are dealing with and why it will be difficult to control the situation.”

Some scientists are looking at spraying cattle feed with probiotics to reduce the number of E. coli cells. Treating food with gamma irradiation to kill pathogenic organisms is another possibility. But in the end, Ferroni said it comes down to common sense precautions such as ensuring the quality of food being transported to processing plants or markets, and educating food handlers and the general public about personal hygiene.