Thread: When E. coli took on a mean streak

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When E. coli took on a mean streak

Two decades ago, the once-harmless bug swapped genes with a dysentery-causing microbe, and now poses a lethal threat
BY DELTHIA RICKS
Newsday Staff Writer

December 10, 2006

At some point in the early 1980s, a harmless form of bacterium known as E. coli swapped genes with the more potent dysentery-causing Shigella microbe, paving the way for a new and potentially lethal danger that increasingly has invaded the food supply.

Even though the United States has one of the safest food supplies in the world, the emergence of an emboldened E. coli strain has in the past two and half decades produced new levels of concern - and now demands from consumer advocates that food producers re-emphasize safety.

The Centers for Disease Control and Prevention estimates 73,000 people a year are infected with E. coli O157:H7, the strain that emerged after the unexpected gene swap. Most of those infections occur as a result of contaminated beef, but an increasing number are attributable to tainted produce.

Indeed, the bug is the sole suspect in an expanding outbreak linked to Taco Bell restaurants on Long Island and elsewhere in the Northeast, and stands as the prime perpetrator in a deadly outbreak in September caused by contaminated spinach.

A scant 12 years ago, the CDC estimated the strain, which is capable of triggering bloody diarrhea, kidney failure and death, caused only 20,000 human infections annually.

Many food safety experts are sounding alarms and calling for tighter regulation of foods from farm to fork.

Robert Gravani, a professor of food science at Cornell University, said an increasing desire for fresh - and sometimes exotic - vegetables year-round has created a vast and complex food distribution chain. Such complexity has opened a window to potential contamination - for example, when fresh summer fruits from abroad are sold in the United States during winter.

"We've had experience with this organism in ground beef," said Gravani, referring to numerous recalls of meat tainted with E. coli. As a result, the U.S. Department of Agriculture requires guidelines on safe handling and cooking practices for consumers on all meat packages.

The microbe's presence on produce, he said, is a newer, evolving story in food-borne illnesses. Gravani sees a learning curve unfolding as health authorities grapple with a growing number of foods that become tainted.

A problem with vegetables eaten raw is that the contamination cannot be washed away because the microbe becomes imbedded in the plant. Heating, however, can destroy it.

Over the years, the organism has tainted apple cider, sprouts, cantaloupes, lettuce and spinach, to name a few.

Twenty-one outbreaks involving green leafy vegetables - some marked by fatalities - have been traced to farms in California's Central Valley in the last decade, including the spinach involved in the September episode. Nearly 200 were sickened and three died in that wave of infections. Four ranches were found to have cattle feces with E. coli that matched the genetic fingerprint of the bacteria that sickened people.

Changes in handling food

Gravani, who conducts classes throughout New York for food safety inspectors, said the increasing virulence of microorganisms has created a need to change a range of farming and food-handling practices.

"With produce, you have to be aware of water: water used in irrigation, water used for washing and water used in hypercooling. You have to be aware of where the water is coming from and certain that it is potable," he said.

Key among those concerns is certainty that the water is not tainted by fecal matter from any source, including manure fertilizers or compost containing manure. E. coli, he underlined, is a fecal bacterium.

Fecal matter in food can have deadly consequences.

In 2003, green onions grown in Mexico were tainted with hepatitis A, a fecal virus. Four people in a western Pennsylvania outbreak died and more than 600 grew ill after eating onions at Chi-Chi's restaurants.

"This is going to be a recurring problem because of the way we handle foods," said Dr. Pascal James Imperato, a professor of preventive medicine at SUNY Downstate Medical Center in Brooklyn.

Imperato emphasized that while the U.S. Food and Drug Administration has published guidelines for vegetable farmers, the agency has no regulatory authority to ensure compliance. Additionally, the FDA has few inspectors to routinely check on voluntary adherence.
Back-to-back outbreaks - first with spinach and now with products sold through Taco Bell - underscore the public's vulnerability when there is a breakdown in food safety, Imperato said.

Yet it wasn't always that way with E. coli, a bacterium that exists in hundreds of strains - most of them mild - including those inhabiting human intestines that aid in digestion.

Mutation into toxin producer

A shocking mutation in the genome of a bovine strain in the early 1980s forever changed how scientists regard the microbe.

Imperato said somehow, somewhere, a mild E. coli strain exchanged genes with Shigella, a bacterium that produces a toxin and causes deadly dysentery.

The swap transformed the bovine strain into a toxin-producing bug that is harmless in cattle but a nightmare in humans. The exchange was identified in 1982.

Imperato said it is the toxin that causes complications that lead to death in humans.

Following the spinach scare, the Center for Science in the Public Interest, a consumer group, called on the FDA to broaden its authority and enforce better sanitation practices on farms and in produce-processing plants.

Caroline Smith DeWaal, the center's food safety director, said farmers must be aware that emerging bacteria have evolved frightening characteristics.

"We're proposing that the FDA put in place a process-control system similar to what was done in the meat industry following the Jack-in-the-Box outbreak," she said.

In 1993, hundreds became sick and four children died when they ate E. coli O157:H7-tainted hamburger from the fast-food outlet.

"We want preventive control systems rather than waiting for a disaster to happen and then recalling a product. The meat industry is now regulated from the farm through retail outlets," DeWaal said.

Still, Francisco Diez, an associate professor of food science at the University of Minnesota, found there is much about E. coli O157:H7 that scientists are only starting to learn.

Scientists were surprised to learn the microbe is most prevalent in cattle during summer, and is present in crops usually in summer and fall.

"Whenever you walk onto a farm, depending on the season, 10 to 20 percent of all animals may test positive, especially in summer. In winter, the number of positive animals decreases to less than 5 percent," he said.

"This seasonality is also linked to the timing of human outbreaks. Most human outbreaks are occurring in late summer or fall. We really don't have an explanation for this. But it's something that is drawing a lot of interest."

Keeping illness out of our food

Experts' suggestions to prevent E. coli contamination at the source:

Use potable water to irrigate crops to avoid contamination.

Keep all animals away from crops, especially crops eaten raw, to avoid contamination from fecal matter that may contain a potentially lethal bacterial superstrain.
Make sure crops are refrigerated at all times after harvesting.

Ensure that water used to mist produce is from a potable source and is maintained at a proper temperature.

The big picture

Number of people affected (number of outbreaks) of food-borne illness linked to these food categories, 1990-2004

Produce 31,496

Poultry 16,280

Beef 13,220

Eggs 11,027

Seafood 9,969

Produce types

Number of people affected (number of outbreaks) of food-borne illness linked to these produce types,

1990-2004

Vegetables 11,957

Produce dishes 11,255

Fruits 8,284

SOURCES: U.S. FOOD AND DRUG ADMINISTRATION; CENTER FOR SCIENCE IN THE PUBLIC INTEREST; ASSOCIATED PRESS

Some recent outbreaks

November 2003

Hepatitis A traced to green onions at Chi-Chi's

September 2006

E. coli in fresh spinach, various distributors

December 2006

Listeria bacteria possibly in strawberries, Jamba Juice

October 2005

E. coli in prepackaged salads, Dole Food

November 2006

Salmonellatainted tomatoes, various eateries

December 2006

E. coli in green onions at Taco Bells on Long Island, elsewhere

I always plant my own garden, but it will be bigger this upcoming year. We can't hide from everything, but I'll do my best to avoid the lack of sanitation that is plaguing the US. This is a great reason to start a diet!