Food Poisoning Diagnosis

  • Diagnosis

    Food poisoning is a gastrointestinal illness that results from ingesting food-borne microorganisms, their toxins, parasites, or chemicals. Every year, one in five Americans will suffer a bout of food poisoning—usually after eating something contaminated with bacteria such as an undercooked hamburger or a potato salad that has been sitting out all day at a picnic. Commonly referred to as “the stomach flu” or “the 24-hour bug,” food poisoning typically strikes within hours or days of eating the offending food. It usually starts with a wave of nausea followed by vomiting and/or diarrhea. In healthy adults, most cases are mild—albeit unpleasant—and run their course within a day or two. But in children, older adults, and people with weakened immune systems, food poisoning can be dangerous. Although it is rare, food poisoning such as botulism can be fatal.

    Food poisoning is usually caused by any one of a number of bacteria. Viruses, parasites, and chemicals are other causes Table 01. Many types of bacteria that live in the intestines of humans and animals can cause illness when they get into the food that we eat. Meat and poultry are sometimes contaminated during slaughter. Organisms also may be transferred to food by anyone who has not washed their hands after coming into contact with human or animal feces.

    Some bacterial organisms make toxins that damage intestinal cells and cause a loss of fluid that contains vital proteins, water, and electrolytes. Viruses and parasites can also attack the intestinal lining and wreak havoc when they enter your digestive system. Intestinal parasites like Giardia and Cryptosporidium are usually picked up by drinking contaminated water. Chemical toxins may be man-made (drugs—pharmaceutical or illegal) or occur naturally in plants or fish.

    Table 1.  Common Bacteria That Cause Food Poisoning

    Bacteria Comments
    Campylobacter These bacteria are very common in poultry. It is believed that half of all raw chicken is contaminated with it. Other sources of infection include unpasteurized milk and contaminated water.
    Clostridium botulinum This bacterium is common in soil, and can lead to a deadly illness called botulism. Food-borne botulism is rare because the organism needs specific conditions in order to produce toxins; namely a temperature above 38? Fahrenheit and a lack of oxygen. Poorly canned vegetables and fruits are a potential source for this type of food poisoning, but modern canning methods have almost done away with the problem. Honey can be a source of infant botulism.
    E. coli These bacteria are the most common cause of traveler?s diarrhea. Drinking water?even ice cubes floating in a drink?or eating peeled fruit while in a foreign country can lead to infection. Undercooked ground beef and unpasteurized milk are other havens for E. coli. There have been several recent nationwide E. coli outbreaks in which the culprit was a vegetable, rather than meat or water. An outbreak in 2006 affected more than 150 people and resulted in 3 deaths. Public health officials eventually traced the outbreak to raw spinach, but the ultimate source of contamination remains unknown. .
    Listeria monocytogenes This bacterium is usually picked up from soft cheeses, undercooked meats, and foods prepared in delicatessens.
    Salmonella These bacteria are commonly found in raw or undercooked meat, poultry, and raw eggs.
    Shigella These bacteria thrive in food that is left out for long periods.
    Staphylococcus These bacteria are usually picked up from mayonnaise-based salads (tuna salad, potato salad, egg salad) and cream-filled desserts.
    Vibrio Normal marine bacteria. Usually acquired by eating raw mollusks.

    Improper storage, handling, or preparation of food increases the likelihood of food poisoning. Practically every food contains some bacteria, but most of them are harmless or get destroyed by cooking. It's when foods are improperly stored, handled, or cooked that they become a threat. The proper temperature is key: refrigeration keeps most bacteria at bay, and cooking food thoroughly at a high heat kills nearly all types of bacteria. However, if foods are not refrigerated or cooked at the right temperature—particularly meat and poultry—they can be toxic. Undercooked beef and poultry are common sources of infection. Raw foods, too, can make you sick; raw eggs sometimes harbor harmful bacteria, making Caesar salads and cookie dough risky. In addition, raw fish—especially from polluted waters—served as sushi or sashimi can be a dangerous menu choice. Shellfish such as clams, oysters, and muscles live by filtering water, so there is a good chance they could make you sick if eaten raw.

    Food preparation is another avenue for contamination. Food-handlers who do not wash their hands before touching food or fail to sterilize cutting boards, knives, and other cooking utensils can carry harmful bacteria and viruses into the dishes they prepare. Delis, restaurants, and cafeterias have been responsible for many food poisoning outbreaks.

    Eating certain foods can increase risk of food poisoning. Chemical food poisoning occurs when poisonous plants or animals are eaten. There are several species of mushroom that are poisonous, as well as certain types of fish. The Japanese ruddy fish is a notorious deadly meal. Even mackerel and tuna can cause potentially deadly allergic reactions in some people. Shellfish can produce poisons that cause paralysis—even after it has been cooked.

    Sudden nausea, vomiting, abdominal pain, and diarrhea are typical symptoms of food poisoning. Depending on the cause, fever and chills, weakness, headache, and bloody stool may be present as well Table 02. The symptoms and severity of food poisoning depend on what has caused it and the amount of food that has been eaten. Mild food poisoning is often chalked up to “the stomach flu,” and typically leaves you with no appetite and feeling sick to your stomach. Abdominal cramping, vomiting, and diarrhea tend to be at their worst at the start of the illness; and the symptoms taper off over the course of a few days, but you'll still likely feel weak and tired. Severe vomiting and diarrhea can cause dehydration and lead to electrolyte imbalances, which can be serious and require medical attention.

    Table 2.  Symptoms of Common Bacterial Food Poisonings

    Bacterial poisoning Symptoms
    Camplyobacteriosis Fever, diarrhea, and bloody stool two to five days after eating a contaminated food. Usually mild, the infection can trigger Guillain-Barre syndrome (a problem in which the immune system attacks the body?s nerves and may cause paralysis or even death).
    Botulism Eye problems such as double vision, drooping eyelids and an inability to focus on nearby objects; difficulty swallowing or breathing; nausea, vomiting, cramps, and diarrhea, usually within 18-36 hours of eating a contaminated food. The infection is very serious and can be fatal.
    E. coli Nausea, vomiting, and diarrhea; headaches and muscle aches within one to eight days of eating a contaminated food. In children, the infection could cause kidney failure and death.
    Listeriosis Fever, muscle aches, fatigue, and nausea. Some victims develop meningitis. The infection can be a serious threat to pregnant women who may deliver prematurely, or have an infected infant or stillbirth.
    Salmonellosis Nausea, vomiting, cramps, and diarrhea within 48 hours of eating the offending food. The illness can be fatal in infants, older adults, and people with weakened immune systems.
    Shigellosis Abdominal cramps and pain, nausea and vomiting, watery diarrhea, bloody stool, and fever within one to seven days. The infection can be serious in infants, older adults, and people with weakened immune systems.
    Staphylococcus Diarrhea and nausea/vomiting within two to eight hours.
    Vibrios Diarrheal illness or sepsis syndrome in compromised hosts

    Your doctor will suspect food poisoning if you have sudden gastrointestinal symptoms after eating or drinking a suspicious food or beverage. Lab studies can reveal the offending organism. If you have diarrhea and vomiting while traveling in a foreign country, or if you and other people who have eaten at the same place all come down with symptoms, your doctor will suspect food poisoning. To uncover the exact cause of your food poisoning, your doctor may ask for a sample of your stool, vomit, and/or blood. He or she may also wish to look at the suspicious dish, if possible, that landed you in the office. If your symptoms last more than a few days, he or she may want to examine your bowel using a colonoscope (a flexible, lighted viewing tube that is inserted through the rectum to allow a close look at the colon).

    Properly refrigerating and freezing food is key to preventing bacterial contamination. Refrigeration keeps potentially harmful bacteria from growing. Make sure your refrigerator is set below 40°F and that your freezer stays below zero. Double-check that the settings are accurate with a thermometer—especially during warmer months. When unpacking groceries, first put raw meat and poultry into the refrigerator on the bottom shelf to prevent the juices from dripping, and do not keep them for more than a few days or freeze them. When defrosting meat and poultry, use the refrigerator instead of leaving it out on the counter. If you plan to cook frozen food right away, you can use the microwave for defrosting. Use the refrigerator for marinating meat and poultry. In addition, be sure to refrigerate leftovers right away. Divide stews and casseroles into smaller portions so they cool faster.

    Cooking food thoroughly at a high heat kills most bacteria.

    • If you are cooking meat or poultry, make sure that it is cooked through (no longer pink)
    • When you are cooking poultry, the juices should run clear
    • Serve food as soon as possible after you have prepared it. Don’t leave food on the stove or out at room temperature for too long

    If you are having a salad, wash all the vegetables thoroughly first.

    Good personal and kitchen hygiene can lower the likelihood of food poisoning.

    • Wash your hands with soap and warm water for at least half a minute before and after handling food, especially raw meat and poultry
    • Always wash your hands after going to the bathroom
    • Use a fresh towel or paper towels to dry your hands
    • After cutting raw meat or poultry, wash the cutting board and knife with warm soapy water. You can put plastic cutting boards in the dishwasher. Wooden cutting boards should be washed with hot soapy water and a disinfectant
    • If you are barbequing, don’t serve cooked meat on the same plate that the raw meat was on and don’t use cooking utensils for serving

    Don’t buy food that looks or smells bad. Check meat, fish, and poultry for signs of freshness. Never purchase it past the sell-by date, and avoid cuts that look or smell spoiled. Steer clear of canned goods if the can is rusty, leaky, or bulges. It is a good idea to avoid foods that contain raw fish (sushi, sashimi) or raw eggs (egg nog, Caesar salad, cake batter, cookie dough); mayonnaise-based salads and deli meats that have been left out at room temperature for long periods of time should also be avoided.

  • Prevention and Screening

    Properly refrigerating and freezing food is key to preventing bacterial contamination. Refrigeration keeps potentially harmful bacteria from growing. Make sure your refrigerator is set below 40°F and that your freezer stays below zero. Double-check that the settings are accurate with a thermometer—especially during warmer months. When unpacking groceries, first put raw meat and poultry into the refrigerator on the bottom shelf to prevent the juices from dripping, and do not keep them for more than a few days or freeze them. When defrosting meat and poultry, use the refrigerator instead of leaving it out on the counter. If you plan to cook frozen food right away, you can use the microwave for defrosting. Use the refrigerator for marinating meat and poultry. In addition, be sure to refrigerate leftovers right away. Divide stews and casseroles into smaller portions so they cool faster.

    Cooking food thoroughly at a high heat kills most bacteria.

    • If you are cooking meat or poultry, make sure that it is cooked through (no longer pink)
    • When you are cooking poultry, the juices should run clear
    • Serve food as soon as possible after you have prepared it. Don’t leave food on the stove or out at room temperature for too long

    If you are having a salad, wash all the vegetables thoroughly first.

    Good personal and kitchen hygiene can lower the likelihood of food poisoning.

    • Wash your hands with soap and warm water for at least half a minute before and after handling food, especially raw meat and poultry
    • Always wash your hands after going to the bathroom
    • Use a fresh towel or paper towels to dry your hands
    • After cutting raw meat or poultry, wash the cutting board and knife with warm soapy water. You can put plastic cutting boards in the dishwasher. Wooden cutting boards should be washed with hot soapy water and a disinfectant
    • If you are barbequing, don’t serve cooked meat on the same plate that the raw meat was on and don’t use cooking utensils for serving

    Don’t buy food that looks or smells bad. Check meat, fish, and poultry for signs of freshness. Never purchase it past the sell-by date, and avoid cuts that look or smell spoiled. Steer clear of canned goods if the can is rusty, leaky, or bulges. It is a good idea to avoid foods that contain raw fish (sushi, sashimi) or raw eggs (egg nog, Caesar salad, cake batter, cookie dough); mayonnaise-based salads and deli meats that have been left out at room temperature for long periods of time should also be avoided.

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