Escherichia
coli O157:H7 is an emerging cause of
foodborne illness. An estimated 73,000 cases
of infection and 61 deaths occur in the United States each year.
Infection often leads to bloody diarrhea, and occasionally to kidney
failure. Most illness has been associated with eating undercooked,
contaminated ground beef. Person-to-person contact in families and child
care centers is also an important mode of transmission. Infection can
also occur after drinking raw milk and after swimming in or drinking
sewage-contaminated water.
Consumers can prevent E. coli
O157:H7 infection by thoroughly cooking ground beef, avoiding
unpasteurized milk, and washing hands
carefully.
Because the organism lives in the intestines of healthy cattle,
preventive measures on cattle farms and during meat processing are
beinginvestigated.
What
is
Escherichia
coli
O157:H7?
E. coli O157:H7 is one of hundreds
of strains of the bacterium Escherichia
coli. Although most strains are harmless and
live in the intestines of healthy humans and animals, this strain
produces a powerful toxin and can cause severe illness.
E. coli O157:H7 was first
recognized as a cause of illness in 1982 during an outbreak of severe
bloody diarrhea; the outbreak was traced to contaminated hamburgers.
Since then, most infections have come from eating undercooked ground
beef.
The combination of letters and numbers in the name of the bacterium
refers to the specific markers found on its surface and distinguishes it
from other types of E. coli.
How is
E.
coli
O157:H7 spread?
The organism can be found on a small number of cattle farms and can live
in the intestines of healthy cattle. Meat can become contaminated during
slaughter, and organisms can be thoroughly mixed into beef when it is
ground. Bacteria present on the cow's udders or on equipment may get
into raw milk.
Eating meat, especially ground beef, that has
not been cooked sufficiently to kill E. coli
O157:H7 can cause infection. Contaminated meat looks and smells normal.
Although the number of organisms required to cause disease is not known,
it is suspected to be very small.
Among other known sources of infection are
consumption of sprouts, lettuce, salami,
unpasteurized milk and juice, and swimming in or drinking
sewage-contaminated water.
Bacteria in diarrheal stools of infected
persons can be passed from one person to another if hygiene or
handwashing habits are inadequate.
This is particularly likely among toddlers who are not toilet trained.
Family members and playmates of these children are at high risk of
becoming infected.
Young children typically shed the organism in their feces for a week or
two after their illness resolves. Older children rarely carry the
organism without symptoms.
What illness does
E.
coli
O157:H7 cause?
E. coli O157:H7 infection often
causes severe bloody diarrhea and abdominal cramps; sometimes the
infection causes nonbloody diarrhea or no
symptoms. Usually little or no fever is present, and the illness
resolves in 5 to 10 days.
In some persons, particularly children under 5 years of age and the
elderly, the infection can also cause a complication called hemolytic
uremic syndrome, in which the red blood
cells are destroyed and the kidneys fail. About 2%-7% of infections lead
to this complication. In the United States, hemolytic
uremic syndrome is the principal cause of
acute kidney failure in children, and most cases of hemolytic
uremic syndrome are caused by E.
coli O157:H7.
How is
E.
coli
O157:H7 infection
diagnosed?
Infection with E. coli O157:H7 is
diagnosed by detecting the bacterium in the stool. Most laboratories
that culture stool do not test for E. coli
O157:H7, so it is important to request that the stool specimen be tested
on sorbitol-MacConkey (SMAC) agar for this
organism. All persons who suddenly have diarrhea with blood should get
their stool tested for E. coli
O157:H7.
How is the illness treated?
Most persons recover without antibiotics or other specific treatment in
5-10 days. There is no evidence that antibiotics improve the course of
disease, and it is thought that treatment with some antibiotics may
precipitate kidney complications. Antidiarrheal
agents, such as loperamide (Imodium), should
also be avoided.
Hemolytic uremic syndrome is a
life-threatening condition usually treated in an intensive care unit.
Blood transfusions and kidney dialysis are often required. With
intensive care, the death rate for hemolytic uremic
syndrome is 3%-5%.
What are the long-term consequences of
infection?
Persons who only have diarrhea usually recover completely.
About one-third of persons with hemolytic uremic
syndrome have abnormal kidney function many years later, and a few
require long-term dialysis. Another 8% of persons with hemolytic
uremic syndrome have other lifelong
complications, such as high blood pressure, seizures, blindness,
paralysis, and the effects of having part of their bowel removed.
What can be done to prevent the infection?
E. coli O157:H7 will continue to be
an important public health concern as long as it contaminates meat.
Preventive measures may reduce the number of cattle that carry it and
the contamination of meat during slaughter and grinding. Research into
such prevention measures is just beginning.
What can you do to prevent
E.
coli
O157:H7 infection?
Cook all ground beef and hamburger thoroughly. Because ground beef can
turn brown before disease-causing bacteria are killed, use a digital
instant-read meat thermometer to ensure thorough cooking. Ground beef
should be cooked until a thermometer inserted into several parts of the
patty, including the thickest part, reads at least 160º F. Persons who
cook ground beef without using a thermometer can decrease their risk of
illness by not eating ground beef patties that are still pink in the
middle.
If you are served an undercooked hamburger or other ground beef
product in a restaurant, send it back for further cooking. You may want
to ask for a new bun and a clean plate, too.
Avoid spreading harmful bacteria in your kitchen. Keep raw meat
separate from ready-to-eat foods. Wash hands, counters, and utensils
with hot soapy water after they touch raw meat. Never place cooked
hamburgers or ground beef on the unwashed plate that held raw patties.
Wash meat thermometers in between tests of patties that require further
cooking.
Drink only pasteurized milk, juice, or cider. Commercial juice with
an extended shelf-life that is sold at room temperature (e.g. juice in
cardboard boxes, vacuum sealed juice in glass containers) has been
pasteurized, although this is generally not indicated on the label.
Juice concentrates are also heated sufficiently to kill pathogens.
Wash fruits and vegetables thoroughly, especially those that will not
be cooked. Children under 5 years of age,
immunocompromised persons, and the elderly should avoid eating
alfalfa sprouts until their safety can be assured. Methods to
decontaminate alfalfa seeds and sprouts are being investigated.
Drink municipal water that has been treated with chlorine or other
effective disinfectants.
Avoid swallowing lake or pool water while swimming.
See more information about this.
Make sure that persons with diarrhea, especially children, wash their
hands carefully with soap after bowel movements to reduce the risk of
spreading infection, and that persons wash hands after changing soiled
diapers. Anyone with a diarrheal illness
should avoid swimming in public pools or lakes, sharing baths with
others, and preparing food for others.
For more information about reducing your risk of
foodborne illness, visit the US Department of Agriculture’s Food
Safety and Inspection Service website at:
http://www.fsis.usda.gov or the Partnership for Food Safety
Education at: For more advice on cooking ground beef, visit the U.S.
Department of Agriculture web site at:
http://www.fsis.usda.gov/OA/topics/gb.htm
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SALMONELLOSIS (Salmonella)
What is
salmonellosis?
Salmonellosis is an infection
with a bacteria called Salmonella.
Most persons infected with Salmonella develop diarrhea, fever,
and abdominal cramps 12 to 72 hours after infection. The illness
usually lasts 4 to 7 days, and most persons recover without
treatment. However, in some persons the diarrhea may be so
severe that the patient needs to be hospitalized. In these
patients, the Salmonella infection may spread from the
intestines to the blood stream, and then to other body sites and
can cause death unless the person is treated promptly with
antibiotics. The elderly, infants, and those with impaired
immune systems are more likely to have a severe illness.
What sort of germ is Salmonella?
The Salmonella germ is actually a group of bacteria that can
cause diarrheal illness in humans.
They are microscopic living creatures that pass from the feces
of people or animals, to other people or other animals. There
are many different kinds of Salmonella bacteria. Salmonella
serotype
Typhimurium and Salmonella serotype
Enteritidis are the most common in
the United States. Salmonella has been known to cause illness
for over 100 years. They were discovered by
a American scientist named Salmon, for whom they are
named.
How can Salmonella infections be
diagnosed?
Many different kinds of illnesses can cause diarrhea, fever, or
abdominal cramps. Determining that Salmonella is the cause of
the illness depends on laboratory tests that identify Salmonella
in the stools of an infected person. These tests are sometimes
not performed unless the laboratory is instructed specifically
to look for the organism. Once Salmonella has been identified,
further testing can determine its specific type, and which
antibiotics could be used to treat it.
How can Salmonella infections be
treated?
Salmonella infections usually resolve in 5-7 days and often do
not require treatment unless the patient becomes severely
dehydrated or the infection spreads from the intestines. Persons
with severe diarrhea may require
rehydration, often with intravenous fluids. Antibiotics
are not usually necessary unless the infection spreads from the
intestines, then it can be treated with
ampicillin, gentamicin,
trimethoprim/sulfamethoxazole, or
ciprofloxacin. Unfortunately, some
Salmonella bacteria have become resistant to antibiotics,
largely as a result of the use of antibiotics to promote the
growth of feed animals.
Are there long term consequences to
a Salmonella infection?
Persons with diarrhea usually recover completely, although it
may be several months before their bowel habits are entirely
normal. A small number of persons who
are infected with Salmonella, will go on to develop pains in
their joints, irritation of the eyes, and painful urination.
This is called Reiter's syndrome. It can last for months or
years, and can lead to chronic arthritis which is difficult to
treat. Antibiotic treatment does not make a difference in
whether or not the person later develops arthritis.
How do people catch Salmonella?
Salmonella live in the intestinal tracts of humans and other
animals, including birds. Salmonella are usually transmitted to
humans by eating foods contaminated with animal feces.
Contaminated foods usually look and smell normal. Contaminated
foods are often of animal origin, such as beef, poultry, milk,
or eggs, but all foods, including vegetables may become
contaminated. Many raw foods of animal origin are frequently
contaminated, but fortunately, thorough cooking kills
Salmonella. Food may also become contaminated by the unwashed
hands of an infected food handler, who forgot to wash his or her
hands with soap after using the bathroom.
Salmonella may also be found in the feces of some pets,
especially those with diarrhea, and people can become infected
if they do not wash their hands after contact with these feces.
Reptiles are particularly likely to harbor Salmonella and people
should always wash their hands immediately after handling a
reptile, even if the reptile is healthy. Adults should also be
careful that children wash their hands after handling a reptile.
What can a person do to prevent this
illness?
There is no vaccine to prevent
salmonellosis. Since foods of animal origin may be
contaminated with Salmonella, people should not eat raw or
undercooked eggs, poultry, or meat. Raw eggs may be unrecognized
in some foods such as homemade hollandaise sauce,
caesar and other homemade salad
dressings, tiramisu, homemade ice cream, homemade mayonnaise,
cookie dough, and frostings. Poultry and meat, including
hamburgers, should be well-cooked, not pink in the middle.
Persons also should not consume raw or
unpasteurized milk or other dairy products. Produce
should be thoroughly washed before consuming.
Cross-contamination of foods should be avoided. Uncooked meats
should be keep separate from produce,
cooked foods, and ready-to-eat foods. Hands, cutting boards,
counters, knives, and other utensils should be washed thoroughly
after handling uncooked foods. Hand should be washed before
handling any food, and between handling different food items.
People who have salmonellosis should
not prepare food or pour water for others until they have been
shown to no longer be carrying the Salmonella bacterium.
People should wash their hands after contact with animal feces.
Since reptiles are particularly likely to have Salmonella,
everyone should immediately wash their hands after handling
reptiles. Reptiles (including turtles) are not appropriate pets
for small children and should not be in the same house as an
infant.
How common is
salmonellosis?
Every year, approximately 40,000 cases of
salmonellosis are reported in the United States. Because
many milder cases are not diagnosed or reported, the actual
number of infections may be thity or
more times greater. Salmonellosis is
more common in the summer than winter.
Children are the most likely to get
salmonellosis. Young children, the elderly, and the
immunocompromised are the most
likely to have severe infections. It is estimated that
approximately 600 persons die each year with acute
salmonellosis.
What else can be done to prevent
salmonellosis?
It is important for the public health department to know about
cases of salmonellosis. It is
important for clinical laboratories to send isolates of
Salmonella to the City, County, or State Public Health
Laboratories so the specific type can be determined and compared
with other Salmonella in the community. If many cases occur at
the same time, it may mean that a restaurant, food or water
supply has a problem which needs correction by the public health
department.
Some prevention steps occur everyday
without you thinking about it. Pasteurization of milk and
treating municipal water supplies are highly effective
prevention measures that have been in place for many years. In
the 1970s, small pet turtles were a common source of
salmonellosis in the United States,
and in 1975, the sale of small turtles was halted in this
country. Improvements in farm animal hygiene, in slaughter plant
practices, and in vegetable and fruit harvesting and packing
operations may help prevent salmonellosis
caused by contaminated foods. Better education of food industry
workers in basic food safety and restaurant inspection
procedures, may prevent cross-contamination and other food
handling errors that can lead to outbreaks. Wider use of
pasteurized egg in restaurants, hospitals, and nursing homes is
an important prevention measure. In the future, irradiation or
other treatments may greatly reduce contamination of raw meat.
What is the government doing about
salmonellosis?
The Centers for Disease Control and Prevention (CDC) monitors
the frequency of Salmonella infections in the country and
assists the local and State Health Departments to investigate
outbreaks and devise control measures. CDC also conducts
research to better identify specific types of Salmonella. The
Food and Drug Administration inspects imported foods, milk
pasteurization plants, promotes better food preparation
techniques in restaurants and food processing plants, and
regulates the sale of turtles. The FDA also regulates the use of
specific antibiotics as growth promotants
in food animals. The US Department of Agriculture monitors the
health of food animals, inspects egg pasteurization plants, and
is responsible for the quality of slaughtered and processed
meat. The US Environmental Protection Agency regulates and
monitors the safety of our drinking water supplies.
How can I learn more about this and
other public health problems?
You can discuss any medical concerns you may have with your
doctor or other heath care provider. Your local City or County
Health Department can provide more information about this and
other public health problems that are occurring in your area.
General information about the public health of the nation is
published every week in the "Morbidity and Mortality Weekly
Report", by the CDC in Atlanta, GA. Epidemiologists in your
local and State Health Departments are tracking a number of
important public health problems, investigating special problems
that arise, and helping to prevent them from occurring in the
first place, or from spreading if they do occur.
What can I do to prevent
salmonellosis?
Cook poultry, ground beef, and eggs thoroughly before eating. Do
not eat or drink foods containing raw eggs, or raw
unpasteurized milk.
If you are served undercooked meat, poultry or eggs in a
restaurant, don't hesitate to send it back to the kitchen for
further cooking.
Wash hands, kitchen work surfaces, and utensils with soap and
water immediately after they have been in contact with raw meat
or poultry.
Be particularly careful with foods prepared for infants, the
elderly, and the immunocompromised.
Wash hands with soap after handling reptiles or birds, or after
contact with pet feces.
Avoid direct or even indirect contact between reptiles (turtles,
iguanas, other lizards, snakes) and infants or
immunocompromised
persons.
Don't work with raw poultry or meat, and an infant (e.g., feed,
change diaper) at the same time.
Mother's milk is the safest food for young infants.
Breast-feeding prevents salmonellosis
and many other health problems.
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