Food Safety: Menacing Microbes
Author: Winston Craig, MPH, PhD, RD.
A recent government-sponsored report estimated that 90 million cases of food-borne illness occur in the United States every year, with about 9,000 deaths from such illnesses. About three-quarters of all illnesses and deaths resulting from food poisoning are caused by eating meat and poultry contaminated by Salmonella and secondarily by Campylobacter bacteria. While the prevalence and danger of contaminated beef is well known, less widely known is the fact that 90 percent of all chickens sold in the United States are contaminated with Campylobacter; and over one-half of the chickens are contaminated with Salmonella.
About 25,000 cases of food-borne illness attributed to E.coli 0157:H7 occur each year resulting in as many as 100 deaths. Children are especially vulnerable to serious complications such as acute kidney failure. Severe abdominal cramps is a common complaint, and infection often produces bloody diarrhea, pus in the stool, and colitis.
E.coli 0157:H7 is a tough and virulent bacterium. As few as 10 bacteria can produce illness, and since it is acid-tolerant it can grow in foods like unpasteurized apple cider and commercial mayonnaise. The most frequently implicated source of infection is undercooked ground beef in hamburgers and hot dogs. Outbreaks of E.coli 0157:H7 infection have been reported from the consumption of lettuce or apple juice. These foods were believed to have been contaminated by animal manure.
A new strain of Salmonella bacteria has recently caught the attention of food scientists and microbiologists. This bacteria is usually found in raw or undercooked eggs, poultry and red meat. CDC estimates it is responsible for as many as 340,000 illnesses a year. Salmonella Typhimurium DT-104 is resistant to five different antibiotics - ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. Drug-resistant bacteria result in part from the common practice of feeding low doses of antibiotics to livestock to promote their health. Over time, the resistant bacteria dominate. Symptoms of salmonella normally include low-grade fever, nausea and diarrhea, and infection. However, in children, the elderly, and other vulnerable groups high fever, severe diarrhea, or life-threatening dehydration may result.
Eggs can also be contaminated with Salmonella bacteria. And the eggs need not be soiled or cracked to be unsafe. Salmonella enteriditis can infect the ovaries of the hen so that the bacteria contaminate inside of the egg as it is forming. Clearly, raw or improperly cooked egg and egg products, such as eggnog and Caesar salad dressing, are considered high risk. Documented outbreaks of Salmonella enteriditis, with associated deaths, have increased over the past 10 years.
Thorough cooking of food does not always eliminate the risk of food poisoning. Food handlers can cross-contaminate food by unhygienic practices. Cooked food can become contaminated when it comes in contact with a dish, utensil, cutting board or counter top that has been contaminated by tainted food. Also, the prions in beef that appear to transmit Creutzfeldt-Jacob disease, a deadly disease in people associated with eating meat from cattle with mad cow disease, are not destroyed by conventional cooking methods.
An increasing number of food-borne illnesses are traced to imported food such as the Mexican strawberries contaminated with hepatitis A and South American fish and shellfish that caused outbreaks of E. coli 0153:H45 and Vibrio cholera. The FDA has only 300 food safety inspectors for the nations 330 sea ports. Furthermore, each inspector is now responsible for almost three times as many food shipments as 5 years ago. Less than one percent of imported food is actually tested for bacterial or chemical contamination. In addition, US customs officials have found importers engaged in many illegal practices including mislabeling food; laundering rotten fish and shellfish with chemicals to alter the look and smell of the food; and falsification of import documents.
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The beta-carotene in carrots and spinach is absorbed three times better from the cooked vegetable than from the raw vegetable.