6 Types of Very Common Toxic Bacteria You Need to Avoid, and Where They're Typically Found
Thousands of different types of bacteria exist naturally
in our environment. Some are necessary and quite healthy,
like probiotics that support digestive health. Others, however,
like the ones you'll read about below, can cause serious disease.
The number of bacteria that can cause illness in humans is
only a small fraction of those that exist. So while it's not
necessary, or even possible, to avoid all bacteria, you should
be aware of these toxic varieties, and how to keep yourself
and your family safe.
Raw shellfish like oysters can contain Vibrio, bacteria
that can cause diarrhea, abdominal cramping and headache.
1. Staphylococcus Aureus
Staphylococcus aureus bacteria are present in the nasal passages,
throats, hair and skin of 50 percent of healthy people, according
to the U.S. Food and Drug Administration (FDA). If concentrated
in large quantities in foods, however, it can cause food poisoning
that results in nausea, vomiting and abdominal cramping.
Foods that are at risk of contamination by Staphylococcus
aureus include dairy, meats, creamy salads (egg salad, chicken
salad, etc.), cream-filled pastries and sandwich fillings.
Food handlers are the main cause of contamination. Although
food poisoning can be serious, staphylococcal food poisoning
usually resolves in two days.
The Staphylococcus aureus bacteria can also cause a much
more serious problem, generically known as staph infections.
Staph infections occur when the bacteria enter the skin via
a puncture or cut. It can also be passed on contaminated surfaces,
through the air and from person to person.
Staph bacteria can cause a number of infections, including
folliculitis, boils, scalded skin syndrome, impetigo, toxic
shock syndrome, and cellulites.
Now, a drug-resistant form of the bacteria, Methicillin-resistant
Staphylococcus aureus (MRSA), is showing up in increasing
numbers in the nation's hospitals and intensive care units.
Worse still, a particularly virulent strain, known as the
community strain, is now able to infect otherwise healthy
"Unlike traditional MRSA the community strain is very
fit -- it causes infection in healthy people," said Centers
for Disease Control and Prevention (CDC) epidemiologist Dr.
Monina Klevens. "When it is introduced into a hospital,
where ill patients are more vulnerable to infection, it has
the potential to cause significant morbidity and mortality."
What can you do? Wash your hands frequently (including
under your nails), bathe daily and keep any cuts clean and
well covered. Also, keep foods hot or refrigerated until serving.
Eating food infected with Vibrio causes diarrhea, abdominal
cramping, nausea and headache. In people with weakened immune
systems, certain varieties of Vibrio can infect the bloodstream
and be life-threatening.
"Humans become infected when they eat raw or undercooked
shellfish. Each year in the United States, Vibrio cause an
estimated 8,000 infections and 50 deaths," said Dr. Nicholas
A. Daniels of the University of California, San Francisco.
"Shellfish, particularly oysters since they are filter-feeders,
concentrate the bacteria in their tissues."
What can you do? Only eat shellfish, such as oysters,
that has been thoroughly cooked, particularly in the warm-weather
months, when related infections are more common. The bacteria
also exist in seawater and can infect an open wound while
3. Listeria monocytogenes
Eating food contaminated with listeria bacteria can cause
an infection called listeriosis, along with meningitis, encephalitis
and intrauterine infections. According to the CDC, an estimated
2,500 persons become seriously ill with listeriosis each year
and, of these, 500 die.
While healthy people may not experience any symptoms from
ingesting listeria, pregnant women, newborns and those with
weakened immune systems can become seriously ill. In pregnant
women, the infection may cause a flu-like illness, however
can lead to miscarriage, stillbirth, premature delivery or
infection of the newborn.
Listeria is found in soil and water, and therefore can contaminate
raw foods of all kinds, including fruits, vegetables, meats,
seafood and dairy products. It can also contaminate soft cheeses
and cooked meats like hot dogs and deli meats during packaging.
What can you do? Avoid eating raw or undercooked meats
and dairy and wash all fruits and vegetables thoroughly before
eating. Also wash your hands, cutting boards and counter surfaces
thoroughly after handling uncooked foods. Pregnant women and
others at high risk may also want to avoid:
Hot dogs and deli meats, unless they're reheated until
Getting fluid from hot dog and lunchmeat packages on
other foods, utensils, etc.
Soft cheeses such as feta, Brie, Camembert, blue-veined
cheeses, Mexican-style cheeses and Panela (unless the
label states they are made from pasteurized milk; though
pasteurization can kill nutritional value, its benefit
is the elimination of bacteria such as this)
Refrigerated pâtés, meat spreads and smoked
seafood (unless it is part of a cooked dish).
4. Clostridium botulinum
Clostridium botulinum bacteria is a nerve toxin that can
cause botulism, a serious paralytic illness. In the United
States, about 110 cases of botulism are reported each year,
according to the CDC. Of these, approximately 25 percent are
food-borne, 72 percent are infant botulism, and the rest are
Food-borne botulism is caused by eating foods that are contaminated
with the botulism toxin. Wound botulism occurs when a wound
is infected with the Clostridium bacteria and infant botulism
is caused by consuming spores of the bacteria, which then
grow in the intestines and release toxins.
Botulism symptoms include double or blurred vision, drooping
eyelids, slurred speech, difficulty swallowing, dry mouth,
and muscle weakness. In infants, symptoms may include lethargy,
constipation, a weak cry and poor muscle tone. If left untreated,
the symptoms will lead to paralysis of the arms, legs, trunk
and respiratory muscles.
Because hot dogs can become contaminated with listeria
-- bacteria that can cause miscarriage and stillbirth
-- during packaging, pregnant women should avoid them
unless they're heated until steaming hot.
What can you do? Home-canned foods, particularly those
with low acid content such as asparagus, green beans, beets
and corn, are often sources of botulism. If you can foods
at home, be sure to strictly follow the proper hygiene procedures.
Other outbreaks have been found in processed foods including
chopped garlic in oil, fermented fish and baked potatoes wrapped
in aluminum foil. If you have herbs in oil, keep them refrigerated,
and keep potatoes baked in aluminum foil hot until eaten or
Honey can contain spores of the Clostridium bacteria, so
avoid giving honey to children less than 1 year old. Wound
botulism can be prevented by seeking medical attention for
infected wounds and not using illegal drugs that are injected
with a needle.
5. Escherichia coli (E. coli)
There are hundreds of strains of E. coli bacteria, most of
which exist harmlessly in humans' intestines. However, certain
strains are toxic and produce a serious infection that causes
bloody diarrhea and sometimes kidney failure.
The CDC estimates that 73,000 cases of infection and 61 deaths
occur from E. coli infection in the United States each year.
Most infections are related to eating undercooked ground beef.
What can you do? You can become infected with E. coli
by eating contaminated food, swimming in or drinking water
that's contaminated by sewage or by picking it up from personal
contact, such as in families and day care centers. To reduce
your risk of E. coli:
Only eat ground beef that has been thoroughly cooked
Wash fruits and vegetables thoroughly before eating
Avoid drinking unpasteurized milk if you can't confirm
the cows from which it came are healthy
Wash your hands frequently
If your child is in a day care center, be sure that the
employees wash their hands after changing diapers, and
that children wash their hands after using the bathroom
6. Legionella pneumophila
This bacteria leads to an infection called legionellosis.
There are two forms of legionellosis:
Legionnaires' disease: the severe form of the infection,
which includes pneumonia. Between 8,000 and 18,000 people
are hospitalized with Legionnaires' disease in the United
States each year, according to the CDC.
Pontiac fever: a milder illness. Symptoms, which include
fever, headaches and muscle aches, go away without treatment.
Legionella bacteria are found in water, particularly warm
water such as is found in hot tubs, cooling towers, hot water
tanks, large plumbing systems and parts of air-conditioning
systems in large buildings.
What can you do? You can become infected with Legionnaires'
disease by breathing in mist from water that is contaminated.
More common sources include whirlpool spas that are not properly
cleaned, and contaminated water used for drinking or bathing
on cruise ships or in hotels.
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of the American Medical Association, 2000 Sep 27;284(12):1541-5
Division of Bacterial and Mycotic Diseases