COLUMN ONE : Battling an Elusive Bacterium : A mysterious strain of <i> E. coli </i> is blamed for increasing outbreaks of disease. Children and the elderly are the most vulnerable to the sometimes fatal infection.
The number of cases was insignificant at first: two or three each summer in Minnesota since the early 1980s.
But in the summer of 1988, state health officials were stunned when the same mysterious bacterium--which is carried primarily in meats and raw milk--spread through a day-care center, afflicting 23 of 80 children with bloody diarrhea and landing three in an intensive-care unit with a rare kidney disorder. The illness struck similar numbers of children in 1989.
Physicians there are bracing for more cases of the illness this summer, as are health officials in other parts of the nation and in Canada. Since the strange food-borne bacterium was identified in 1982, sporadic outbreaks have increased steadily. While many people who come in contact with the bacterium do not become ill, the organism has caused severe illness in others, and several deaths in the United States.
There have been large outbreaks in Washington state and in Cabool, Mo., where 200 residents became ill in January. In 1985, 73 residents and staff members of a nursing home in Ontario, Canada, were stricken. Eleven of them died.
The U.S. Centers for Disease Control, U.S. Department of Agriculture, public health departments in at least half a dozen states, and the American National Cattlemen’s Assn. are trying to determine where the perplexing bacterium comes from and how to control it.
“We’recoming into the height of the season--summer--and we expect to see more outbreaks again,” said Dr. Edward Belongia, an epidemiologist for the Minnesota Department of Health. “We just finished investigating an outbreak two weeks ago. We think it’s a very, very important public health problem.”
The mysterious strain is a variation of Escherichia coli, a bacterium found in all humans. More than 100 strains of E. coli have been identified, but the new strain is the first that can trigger deadly complications, said John Kaneene, a professor of epidemiology at Michigan State University’s College of Veterinary Medicine, who is studying the outbreaks.
At a time when Americans are increasingly nervous about the safety of food, public health and agricultural officials are struggling to find ways to arrest an organism whose appearance is becoming more frequent--and more worrisome.
While health officials downplay public fears, contending that food is generally very safe, outbreaks of illnesses caused by food-borne bacteria can happen with relative ease. Most outbreaks are precipitated by mistakes in food handling, such as contamination of a food product or improper cooking, experts say.
In 1985, for example, contaminated milk was blamed for more than 16,000 cases of salmonella in Chicago. Also in 1985, contaminated Mexican-style cheese caused an outbreak of listeriosis in California that led to 48 deaths.
Pesticides and additives rank high in public concerns over food safety, but naturally occurring bacteria and toxins are a more common problem, said Steve Taylor, director of the department of food science and technology at the University of Nebraska and a recent speaker at a national food safety conference.
“It’s just that our food and drug law doesn’t require us to do much about them,” Taylor said.
The mysterious strain of E. coli was identified in 1982, after investigations of outbreaks of diarrhea in Michigan and Oregon. The bacterium has since been isolated in 28 states and in most countries where scientists have looked for it, including Canada, Belgium, Bolivia, Argentina, Britain, Japan, Scotland, Spain and Sri Lanka.
“It’s been in all regions of the country,” said Dr. Patricia Griffin of the CDC’s enteric diseases branch.
Officials believe individuals are exposed to the E. coli bacterium in one of four ways: undercooked meat (including beef, pork, poultry and lamb); cold cuts and lunch meats; raw milk, and person-to-person contact. But the organism, named E. coli O157:H7, has confounded health officials because they have been unable to pinpoint where the bacterium is spreading: in cattle prior to slaughter, during food processing, during preparation of food for cooking, or from person to person.
Outbreaks have been most common in Canada and the northern United States, Kaneene said, but in recent years have spread southward, although federal health officials have not kept an official count of the disease’s victims.
In California, “we’ve had occasional cases but no outbreaks,” said Dr. Ben Werner, chief of the general infectious disease unit of the California Department of Health Services. “We keep waiting for one, especially among our raw milk drinkers in the state. There is about 1% of people in the state who are drinking raw milk still.”
Meat and raw milk producers contend that the E. coli threat is minimal. At Stueve Bros. Farms, where raw milk is produced, officials disagree with health officials who say raw milk is a vehicle for the bacterium.
“E. coli occurs only when you’re not milking clean and you’re not taking care of your equipment right,” said Harold Stueve of the Chino-based company.
According to a cattle industry official, E. coli presents more of an image problem than a health threat.
“It’s certainly a concern,” said Darrell Wilkes, vice president of research and information for the cattlemen’s association in Englewood, Colo. “As you stack up food safety problems, this doesn’t rank very high. But for us, it’s one of those things we want to resolve.”
Increasingly frequent outbreaks of the diarrheal illness, including the Missouri outbreak in which residents were stricken with the bacterium from a contaminated water supply, have prompted a number of research projects.
The cattlemen’s group and the USDA are funding research to test for the bacterium in cuttings of meat during and after processing.
The USDA, U.S. Centers for Disease Control and several state health departments are trying to determine how many dairy cattle are infected with the bacterium before slaughter.
Kaneene, the Michigan State professor, is exploring a theory that the bacterium proliferates in cattle while they are in dirty holding facilities just before slaughter.
In states where outbreaks have occurred, including Washington, Oregon, Minnesota and Michigan, officials are trying to get a handle on who gets sick from the E. coli strain and why.
Children under age 5 and the elderly appear to be most vulnerable to illness from the bacterium, Kaneene said. “But the general population is not immune.”
It is thought that many people carry the particular bacterium and do not become ill. But carriers can pass the infection to another person who can become ill, Kaneene said. This type of transmission commonly occurs in preschools or nursing homes where hygiene is a problem.
After a severe wave of illness in 1987 in Washington state, officials there made E. coli O157:H7 a reportable illness and required laboratories to look for the bacterium in stool tests of people being treated for diarrheal illness. The situation appears to have stabilized there with 166 cases reported in 1988 and 157 in 1989.
In Minnesota, which also requires reporting of E. coli O157:H7, officials prefer to gauge the rate of infection by the number of cases of hemolytic uremic syndrome (HUS), a rare and sometimes fatal kidney disorder strongly linked to the bacterium.
According to Belongia, HUS cases have increased fourfold in Minnesota from 1979 to 1988. About 20 to 30 cases of HUS are now reported each year in the state, mostly in children, he said. An estimated 5% of children with the E. coli infection will develop HUS, he said.
Other states are considering similar reporting requirements, Griffin said. The CDC supports reporting of the illness because no one can say how many people have become infected with the E. coli strain, how many have died from complications, or how widespread the bacterium is.
“It’s difficult to say how common this illness is. But it’s our impression it’s increasing,” Griffin said.
In Canada, where health officials require laboratories to look for the bacterium in stool samples of people being treated for diarrhea, a rapidly increasing rate of E. coli infection has been reported as well as increases in HUS. In the nursing home outbreak in Ontario, 11 of 12 residents who developed HUS died.
The E. coli infection is not a reportable illness in California. Typically, laboratories looking for the cause of a diarrheal illness check for the most common types of bacteria: Campylobacter, salmonella and shigella.
Those studying the E. coli strain agree that people should not eat hamburgers with rare, or pink-colored, meat visible.
High temperatures can kill bacteria on the surface of a steak, Werner said. But hamburger is particularly worrisome because the bacteria, if present, can be distributed throughout the meat when it is ground.
“As I read more and more about E. coli, I don’t eat hamburgers medium-rare any more,” Werner said. “It’s just too dangerous.”
In Calgary, Alberta, where the E. coli infection is common, residents routinely refuse to eat hamburger unless it is cooked well-done, Griffin said.
“Hamburger is not a safe product to eat rare,” she said.
Treating the disease poses unique problems. A Washington state study showed that antibiotics did not influence the symptoms and did not appear to reduce the risk of more serious complications.
To reduce--or stabilize--the number of infections, agricultural and health officials must trace the food product chain from farmyard to kitchen, Kaneene said. Tests to identify the E. coli bacterium in cattle have been inadequate except for a new genetic probe that is much more sensitive and accurate, he said. But the new test is expensive.
“This test is probably one of the most promising areas (to explore) if we want to make a dent in identifying this agent,” he said.
Kaneene advocates that each state’s health and agricultural officials begin surveillance of cattle to identify the bacterium, using the most accurate tests available, and that health officials report infections in humans.
“This should be a reportable disease in all states,” he said.
TAKING PRECAUTIONS
Consumers can take several precautions against food-borne illnesses such as E. coli 0157:H7:
Cook beef, pork, poultry and lamb thoroughly
Cook hamburger well-done so that no pink is apparent
Avoid consuming raw milk
Wash cooking utensils thoroughly after handling raw meat
Wash hands frequently when handling raw meat
SOURCE: U.S. Centers for Disease Control, Michigan State University
