One of summer’s best-loved foods--hot dogs--may pose a health threat to consumers if left uncooked or undercooked, according to laboratory tests conducted for The Times.
The tests found that 20% of the major brand hot dog products tested contained bacteria that most commonly cause flu-like symptoms but can cause serious illness. The presence of the bacterium, Listeria monocytogenes, is troubling because hot dogs are often not thoroughly heated and some people eat them straight out of the package.
Hot dogs are classified by the federal government as a “processed” meat item, meaning that they are required by law to be fully cooked and ready to eat at the time of purchase. Thus, the government does not require cooking instructions on hot dog packaging. As a result, some manufacturers provide cooking guidelines and others do not.
Last year, an advisory issued jointly by the Food and Drug Administration, the U.S. Department of Agriculture and the Centers for Disease Control and Prevention warned people considered to be in high-risk groups to avoid eating delicatessen-type foods, soft cheeses and undercooked chicken because of the listeriosis risk.
The advisory specifically recommended that hot dogs be cooked to “steaming hot"--160 degrees for several minutes--in order to destroy harmful organisms that may be present. Still, food service outlets and consumers often undercook hot dogs. Federal officials caution that extra care be taken when microwaving hot dogs because the fast-cooking ovens may heat unevenly.
Typically, a healthy adult can consume small doses of the bacterium and not develop any illness, although heavily contaminated food may infect otherwise healthy adults. Medical officials do not yet know how many organisms constitute an ineffective dose. The allowable amount of Listeria monocytogenes in fully cooked, ready-to-eat foods, such as hot dogs, is zero in the United States.
Several groups are especially vulnerable to Listeria infection, including pregnant women, infants, the elderly, those with compromised immune systems--such as cancer or AIDS patients--and individuals suffering from cirrhosis, diabetes and ulcerative colitis. According to the CDC, AIDS patients have 300 times the risk of infection than the general population; pregnant women have 20 times the risk of acquiring listeriosis.
When infection does occur, the early symptoms are flu-like, including fever, nausea, vomiting and diarrhea. In advanced stages, listeriosis can cause meningitis and blood infections.
The laboratory tests were conducted for The Times by a federally accredited food laboratory that performs testing for the U.S. Department of Agriculture. USDA-approved laboratory procedures were used to detect this particular pathogen. Testing procedures indicate only whether L. monocytogenes is present, but not the amount of bacteria in the product.
The hot dogs tested for The Times were bought in May and June from six Southern California supermarkets--four chains and two independents--over a two-week period. Five out of 30 hot dog products, from a sample that included 19 brands, tested positive for the Listeria monocytogenes bacteria. A sixth product tested positive for Listeria innocua, a related strain that indicates it is possible for Listeria monocytogenes to grow in the product.
Virtually all varieties of meat and poultry hot dogs were tested by the laboratory. Each of the contaminated samples contained beef as a principal ingredient. The shelf life of a hot dog product is 60 to 100 days, depending on the manufacturer.
In the contaminated group were a 16-ounce package of Bar S Jumbo Franks containing chicken, pork and beef (package expiration code, JUN 23 B1); a 16-ounce package of Hoffy Franks containing pork, beef hearts, beef and turkey (package expiration code, JUN 14); a 16-ounce package of Farmer John Beef Franks (package expiration code, JUN 24-1); a 12-ounce package of Wilson Beef Franks (package expiration code, JUL 03 EB3 ESI 26L), a 16-ounce package of Hoffy Beef Wieners (package expiration code, JUL 24), which contained the related L. innocua, and a 12-ounce package of Mogen David Skinless Kosher Beef Frankfurters (package expiration code, NOV 18), which a company spokesman said expired last November and which should have been taken off the shelf.
Three of four Farmer John products analyzed in the Times study were negative for Listeria and a second Wilson brand hot dog product tested negative.
“Farmer John management is proud of its food safety record,” said Bernard J. Clougherty, vice president. “This year to date, 62 independent laboratory analyses were taken (of Farmer John products) for L. monocytogenes . The results . . . were 61 negative, 1 positive. Unfortunately, due to this microorganism’s characteristic, which is sporadic in nature, even after a long string of negative results, it is not unusual to encounter a positive. This indicates the ubiquity and stealth-like presence of this organism. For this reason, our company will continue our vigilant hygienic programs to ensure we produce products free of this microorganism.”
John Hanes, president of Wilson Foods Corp. in Oklahoma City, Okla., said: “Our main concern is satisfying our customers by providing safe and wholesome products. Listeria is a common bacteria and it is present in all manufacturing situations and in the whole food supply. . . . Listeria is naturally in unprocessed foods and sometimes in processed foods. We will investigate (The Times findings) thoroughly and quickly and in the meantime will continue our efforts to produce safe and wholesome products.”
Richard Berger, vice president for Mogen David Kosher Food Inc., in Newark, N.J., said his brand tested positive because “that product was months past its expiration date . . . which would void the test completely.”
The Mogen David hot dog product tested was purchased in May and had a sell by date of 11/18 stamped on the package, with no year printed on the package. “That particular product was not fit for human consumption at the time it was tested. The test is not relative (sic),” Berger said. He added that the supermarket should have discarded the contaminated product long ago. Mogen David frankfurters are produced by Shofar Kosher Foods in Newark, N.J. Another Shofar product, a 12-ounce package of Shofar Lite Kosher Beef Frankfurters, also was analyzed by The Times and tested negative for Listeria .
“Hoffy has a strict program in effect that is designed to prevent and eradicate all forms of harmful bacteria including, specifically, Listeria monocytogenes , the only form of Listeria which is harmful,” said Laird Robertson, financial adviser and management consultant for Hoffman Bros. Packing. “After learning that the Los Angeles Times had investigated national brands of wieners and found that certain wieners may contain some form of Listeria , Hoffy conducted its own investigation. The company immediately sent a variety of its product to an independent, USDA-approved laboratory for testing. These products were selected from the company’s inventory at random. All test products tested negative for any form of Listeria or other harmful bacteria. The company’s conclusion is that if the tests cited by The Times were conducted accurately, and any Hoffy products tested positive, the problem was most likely the result of mishandling of the product outside Hoffy’s plant.”
Robertson said that six product samples and 18 samples from equipment surfaces taken from the Hoffman Bros. plant all tested negative for Listeria .
Morris Kinne, vice president for Bar-S Foods in Phoenix, said: “Unless we can see the test results and are able to talk with the laboratory technicians about the (testing) protocol used, then it is impossible for us to comment because we are not sure it is an accurate test or one that came out as a false positive.” No other Bar-S products were tested.
The testing procedure performed by the federally accredited laboratory required several steps to determine the presence of the Listeria bacterium. A sample of the food was placed in a broth that changed color during the first two days of testing if harmful organisms were present. If a color change did occur, indicating potential contamination, then a colony of the suspect bacterium was isolated and placed into another enrichment broth. As many as seven days can pass before the organism can be confirmed, according to a Los Angeles microbiologist familiar with the procedure.
The laboratory also used a second, so-called rapid test for Listeria, which yielded preliminary results in 48 hours, as a confirmation procedure for the longer laboratory analyses. In each case, results on both the USDA-approved Listeria tests matched with the more rapid method, a lab representative stated.
The U.S. Public Health Service identifies Listeria monocytogenes as one of the four most serious microbiological threats to the food supply, along with salmonella, Camphylobacter and E. coli 0157:H7 .
A 1992 advisory published by the USDA and the FDA stated that L. monocytogenes is a “remarkably tough organism. It resists heat, salt, nitrite and acidity much better than many organisms.”
Industry spokespersons said that they are aware of the problems with the Listeria bacterium and would tend to agree with the government’s statements.
“Not to make excuses, but under the current technology available, it is impossible to make sure that recontamination does not occur,” said James Marsden, vice president for science and technical affairs for the American Meat Institute, an Arlington, Va.-based trade group representing meat processors.
“The way hot dogs are processed involves a moment of time where they are open to the environment after they are cooked and before the time they are packaged,” Marsden said. “No matter how hard (meat) plants try to control the environment, it is virtually impossible to ensure that the product will not be recontaminated. We know we are vulnerable in this thing because the capability of the process does not allow us to absolutely prevent recontamination.”
Rosemary Mucklow, executive director of the Western States Meat Assn. in Oakland, agreed. “Processing facilities have gone to great efforts to package and process their meat in environmentally safe rooms . . . but we have still not gotten control of this tough little bacteria,” she said.
Listeria monocytogenes is present throughout the environment and has been isolated in soil, sewage, dust and water. However, it was only within the past decade that researchers recognized the bacterium as an agent of food-borne illness. According to the joint FDA-USDA 1992 study, the pathogen is most likely transmitted when animal feces contaminate raw agricultural products.
Listeriosis was responsible for 46 deaths in Southern California, mostly in Los Angeles, during a single 1985 food poisoning outbreak, described by the state Department of Health Services in a January report as the “most deadly food-borne disease outbreak reported” in California during the past 10 years.
At that time, 142 people became seriously ill after eating Jalisco-brand Mexican-style soft cheese contaminated with L. monocytogenes . Since then, government agencies and the food industry have spent millions of dollars attempting to eliminate Listeria , with some success.
The reported number of listeriosis cases in the United States is small compared to other food-borne illnesses, but the disease remains a major concern, according to the CDC, because its fatality rate is about 25% to 35% of reported cases. The CDC estimates that there are about 1,850 cases of listeriosis and 450 deaths in the United States each year.
However, federal officials concede that these figures could be higher because local health officers, physicians and hospital staff are not legally required to report listeriosis infections to the CDC.
Epidemiologists, those who study the path of disease, estimate that 10% or fewer of food-borne illnesses in this country are reported to medical officials. One reason is that a food poisoning can mask itself as a flu and only laboratory tests could determine if an infection were present. Only in severe cases do individuals seek medical attention, often preferring to ride out the normal flu-like symptoms of contamination.
The incubation period of listeriosis, or the time from first exposure until symptoms surface, can be several weeks. “It is difficult to trace back a food (source of contamination) in an ill person after all that time, and even more difficult in mild cases,” Dr. Anne Schuchat, a medical epidemiologist with the CDC, said.
The most recent major outbreak of listeriosis occurred in France last year when 279 illnesses and 63 deaths were reported, according to Schuchat. The outbreak was linked to a delicatessen product, pork tongue in aspic.
Meat processors do not routinely test every shipment for Listeria or other pathogens because of the length of time it takes to receive results. The storage and refrigeration costs would be prohibitive for a plant to hold every processed meat shipment for more than a week until lab results were received. Traditionally, once the product is cooked and packaged it is immediately shipped to wholesale and retail outlets.