AFGALALY محمد عبد الفتاح جلال
AFGALALY محمد عبد الفتاح جلال
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Foodborne DiseasesOverview
Infectious diseases spread through food or beverages are a common,
distressing, and sometimes life-threatening problem for millions of people in
the United States and around the world. The Centers for Disease Control and
Prevention (CDC) estimates 76 million people suffer foodborne illnesses each
year in the United States, accounting for 325,000 hospitalizations and more
than 5,000 deaths.
Foodborne disease is extremely costly. Health experts estimate that the
yearly cost of all foodborne diseases in this country is 5 to 6 billion
dollars in direct medical expenses and lost productivity. Infections with
the bacteria Salmonella alone account for $1 billion yearly in
direct and indirect medical costs.
There are more than 250 known foodborne diseases. They can be caused by
bacteria, viruses, or parasites. Natural and manufactured chemicals in
food products also can make people sick. Some diseases are caused by
toxins (poisons) from the disease-causing organism (germ), others by
bodily reactions to the organism itself. People infected with foodborne
germs may have no symptoms or develop symptoms ranging from mild
intestinal discomfort to severe dehydration and bloody diarrhea.
Recently, public health, agriculture, and environmental officials have
expressed growing concern over keeping the nation's food and water
supply safe from terrorist acts. This bioterrorism threat is being
studied by a number of U.S. agencies, including CDC, Food and Drug
Administration (FDA), Department of Agriculture, Environmental
Protection Agency, and National Institutes of Health.
This fact sheet describes five foodborne diseases caused by bacteria.
PREVENTING FOODBORNE DISEASES
Many times, foodborne diseases are easy to avoid. These are some
basic ways to prevent being infected by most foodborne germs.
Ways to avoid getting sick from specific foodborne germs are
described in the following sections on foodborne diseases.
BOTULISM
Botulism is a rare but serious illness caused by the toxin
produced by Clostridium botulinum bacteria. This toxin
affects the nerves and if untreated, can cause paralysis and
respiratory failure. Each year, U.S. health care providers report
an average of 110 cases of food, infant, and wound botulism to
CDC. About 10 to 30 outbreaks of foodborne botulism are reported
every year. Although this illness does not occur frequently, it
can be fatal if not treated quickly and properly.
Transmission
Often, cases of foodborne botulism come from home-canned foods
with low acid content, such as asparagus, green beans, beets,
and corn. C. botulinum is anaerobic, which means it
can survive and grow with little or no oxygen. Therefore, it
can survive very well in sealed containers. Outbreaks of the
infection, however, are often from more unusual sources such
as chili peppers, tomatoes, and improperly handled baked
potatoes wrapped in aluminum foil.
Symptoms
Symptoms of foodborne botulism usually begin within 18 to
36 hours after eating contaminated food, but can occur in
as few as 6 hours or as much as 10 days afterward.
Diagnosis
A health care provider can use laboratory tests to
identify C. botulinum toxin in your blood or stool if
you are infected.
Treatment
If you are diagnosed early, your health care
provider can treat foodborne botulism successfully
with an antitoxin that blocks the action of the
bacterial toxin circulating in the blood. Although
antitoxin keeps the disease from becoming worse,
it will still take many weeks before you recover.
Your health care provider may try to remove any
contaminated food still in your gut by making you
vomit or by giving you an enema.
People who develop severe botulism experience
breathing failure and paralysis and need to be
put on ventilators (breathing machines).
Prevention
Complications
If left untreated, this illness can cause
paralysis of the arms, legs, trunk, and
muscles that help with breathing. The
paralysis usually improves slowly over
several weeks.
C. botulinum toxin is one of
the most potent toxins known in nature.
Exposure to the toxin, particularly in
an aerosolized form, can be fatal. It
has been made into weapons by rogue
states and is a focus of current efforts
to counter bioterrorism.
C. botulinum can be used
for good purposes
In 1989, FDA approved Botulinum
Toxin Type A, a protein produced by
C. botulinum, as a
treatment for two eye muscle
disorders. In 2000, FDA approved
this toxin to treat cervical
dystonia, a neurological movement
disorder causing severe neck and
shoulder contractions. In April
2002, FDA approved it to temporarily
improve the appearance of moderate
to severe frown lines between the
eyebrows.
CAMPYLOBACTERIOSIS
Campylobacteriosis is an
infectious disease caused by
Campylobacter bacteria.
Campylobacter jejuni, C.
fetus, and C. coli
are the types that usually cause
campylobacteriosis in people.
C. jejuni causes most cases
of the illness.
According to CDC, C. jejuni
is the leading cause of
bacterial diarrheal illness in
the United States, affecting an
estimated 2.4 million people
every year. The bacteria cause
between 5 and 14 percent of all
diarrheal illness worldwide.
C. jejuni primarily affects
children less than 5 years old
and young adults (15 to 29 years
old). Health care providers
report more than 10,000 cases to
CDC yearly. In the United
States, few people die from
Campylobacter infection.
Transmission
You can get infected from
handling raw poultry, eating
undercooked poultry,
drinking nonchlorinated
water or raw milk, or
handling infected animal or
human feces. Most
frequently, poultry and
cattle waste are the sources
of the bacteria, but feces
from puppies, kittens, and
birds also may be
contaminated.
Symptoms
If you are infected with
Campylobacter,
however, you may have no
symptoms. If you do,
they may include
Campylobacteriosis
usually lasts for 2 to
5 days, but in some
cases as long as 10
days. Rarely, some
people have
convulsions with fever
or meningitis.
Diagnosis
A health care
provider can use
laboratory tests
to identify
Campylobacter in
your stool if you
are infected.
Treatment
Most people
infected with
Campylobacter
will get
better with no
special
treatment. If
you need
treatment,
your health
care provider
can prescribe
an antibiotic
such as
ciprofloxacin
or
azithromycin.
Erythromycin
helps treat
diarrhea
caused by
Campylobacter.
If you have
diarrhea, be
sure to drink
plenty of
water.
Prevention
Complications
Some
people
infected
with
Campylobacter
develop
arthritis.
A small
number
of
people
with
campylobacteriosis
may
develop
Guillain-Barré
Syndrome
(GBS),
the
leading
cause of
acute
paralysis
in this
country.
This
rare
condition
develops
from 2
to 4
weeks
after
Campylobacter
infection
and
usually
after
diarrheal
symptoms
have
disappeared.
People
with GBS
suffer
from
increasing
paralysis
of the
limbs
which
lasts
for
several
weeks.
In more
severe
cases,
they
develop
breathing
problems
requiring
very
long
hospital
stays.
E. COLI INFECTION
Certain
types
of
Escherichia
coli
bacteria,
commonly
called
E.
coli,
can
cause
foodborne
illness.
Harmless
strains
of
E.
coli
can
be
found
widely
in
nature,
including
the
intestinal
tracts
of
humans
and
warm-blooded
animals.
Disease-causing
strains,
however,
are
a
frequent
cause
of
both
intestinal
and
urinary-genital
tract
infections.
Several
different
strains
of
harmful
E.
coli
can
cause
diarrheal
disease.
A
particularly
dangerous
type
is
called
enterohemorrhagic
E.
coli,
or
EHEC.
EHEC
often
causes
bloody
diarrhea
and
can
lead
to
kidney
failure
in
children
or
people
with
weakened
immune
systems.
In 1982, scientists identified the first dangerous strain in the United States. The type of harmful E. coli most commonly found in this country is named O157:H7, which refers to chemical compounds found on the bacterium's surface. This type produces one or more related, powerful toxins which can severely damage the lining of the intestines.
Other types, including O26:H11 and O111:H8, also have been found in this country and can cause human disease.
Cattle are the main sources of E. coli O157:H7, but other domestic and wild mammals also can harbor these bacteria.
Transmission
E. coli bacteria and its toxins have been found in
Unsuspecting swimmers have been infected by accidentally swallowing unchlorinated or underchlorinated water in swimming pools contaminated by human feces. You also can get infected by swimming in sewage-contaminated water.
Symptoms
E. coli O157:H7 toxin can damage the lining of your intestine and cause other symptoms including
You might develop low-grade fever or vomiting. Symptoms usually begin from 2 to 5 days after eating contaminated food and may last for 8 days.
Other types of E. coli can cause diarrheal disease
Enterotoxigenic E. coli (ETEC), which produce a toxin similar to Cholera toxin, can cause diarrhea. These strains typically cause so-called travelers diarrhea because they commonly contaminate food and water in developing countries.
Enteropathogenic E. coli (EPEC) are associated with persistent diarrhea (lasting 2 weeks or more) and are more common in developing countries where they can be transmitted by contaminated water or contact with infected animals. Health experts do not know how much disease some of these other types of E. coli cause in the United States.
Diagnosis
Your health care provider can use laboratory tests to identify E. coli in your stool if you are infected.
Treatment
If you are like most people infected with E. coli O157:H7, you will recover within 5 to10 days without treatment. Antibiotics are usually not helpful, and health care experts recommend against taking antidiarrheal medicines.
Prevention
Complications
Hemolytic uremic syndrome (HUS), a serious complication of EHEC, can lead to kidney failure. In North America, HUS is the most common cause of acute kidney failure in children, who are particularly prone to this complication. This life-threatening condition is usually treated in an intensive care unit of a hospital, sometimes with blood transfusions and kidney dialysis.
SALMONELLOSIS
Salmonellosis, or salmonella, is an infection caused by Salmonella bacteria. Salmonella infections are increasing in the United States. Many types of this bacteria cause disease in animals and people. While the occurrence of different types of Salmonella varies from country to country, Salmonella typhimurium and S. enteritidis are the two most commonly found in the United States.
An antibiotic-resistant strain of S. typhimurium, called Definitive Type 104 (DT104), was first found in the United Kingdom and then in the United States. It is the second most common strain (after S. enteritidis) of Salmonella found in humans. This strain poses a major threat because it is resistant to several antibiotics normally used to treat people with Salmonella infections.
Salmonellosis may occur in small, contained outbreaks in the general population or in large outbreaks in hospitals, restaurants, or institutions for children or the elderly. While the disease is found worldwide, health experts most often report cases in North America and Europe. Every year, CDC receives reports of 40,000 cases of salmonellosis in the United States. The agency estimates that 1.4 million people in this country are infected, however, and that 1,000 people die each year with salmonellosis. Symptoms are most severe in the elderly, infants, and people with chronic conditions. People with AIDS are particularly vulnerable to salmonellosis-often suffering from recurring episodes.
Transmission
Salmonella bacteria can be found in food products such as raw poultry, eggs, and beef, and sometimes on unwashed fruit. Food prepared on surfaces that previously were in contact with raw meat or meat products can, in turn, become contaminated with the bacteria. This is called cross-contamination.
In recent years, CDC has received reports of several cases of salmonellosis from eating raw alfalfa sprouts grown in contaminated soil. Salmonella infection frequently occurs after handling pets, particularly reptiles like snakes, turtles, and lizards.
Salmonellosis can become a chronic infection in some people who may not have symptoms. Though they may have no symptoms, they can spread the disease by not washing their hands before preparing food for others. In fact, health care experts recommend that people who know they have salmonellosis not prepare food or pour water for others until a laboratory tests show they no longer carry Salmonella bacteria.
Symptoms
The following symptoms usually begin from 12 hours to 3 days after you are infected.
These symptoms, along with possible nausea, loss of appetite, and vomiting, usually last for 4 to 7 days. Diarrhea can be severe and require hospitalization.
Diagnosis
Your health care provider can use laboratory tests to identify Salmonella in your stool if you are infected.
Treatment
If you are like most people infected with Salmonella, your infection will clear up within 5 to 7 days and you won't need to be treated. If you have severe diarrhea, however, you may need intravenous fluids. If the infection spreads from the intestines into the bloodstream, your health care provider can treat it with antibiotics such as ampicillin.
Prevention
Complications
While most people recover successfully from salmonellosis, a few may develop a chronic condition called Reiter's syndrome. This syndrome can last for months or years and can lead to arthritis. Its symptoms are
Typhoid fever, a more serious disease, results from infection with S. typhi. This disease, which can be fatal if untreated, is not common in the United States. Typhoid fever frequently is found in developing countries, usually in contaminated water. It's also a risk in areas where flooding or earthquakes cause sewer systems to overflow. Appropriate antibiotics are usually effective for treating typhoid fever, although the incidence of antibiotic-resistant S. typhi is increasing is some parts of the world.
SHIGELLOSIS
Shigellosis, also called bacillary dysentery, is an infectious disease caused by Shigella bacteria. Four main types of Shigella cause infection: Shigella dysenteriae, S. flexneri, S. boydii, and S. sonnei. CDC estimates that more than 400,000 cases occur every year in the United States. Health care providers report about 18,000 cases to CDC each year.
Transmission
You can be infected from foodborne Shigella by
S. sonnei is the most common type of Shigella in developed countries, including the United States. Outbreaks of shigellosis frequently occur in tropical or temperate climates, especially in areas with severe crowding and/or poor hygiene that sometimes occur in day care and institutional settings.
Even if you have no symptoms of shigellosis, you can still pass the bacteria to others. An extremely low number of bacteria (10 to 100) is needed to transmit the infection. Therefore, it is commonly transmitted by food service workers who are sick or infected, but have no symptoms, and who do not properly wash their hands after using the toilet. If you know you have shigellosis, you should not prepare food or pour water for others until laboratory tests show you no longer carry Shigella bacteria.
Symptoms
Symptoms usually begin within 2 days after being exposed to Shigella. Symptoms usually are gone within 5 to 7 days.
Treatment
If you have a mild infection, you should get better quickly, without taking medicine. If you need to be treated, your health care provider usually will prescribe an antibiotic such as ampicillin or ciprofloxacin. Antidiarrheal medicines may make the illness worse.
S. flexneri infection can progress to Reiter's syndrome which can last for months or years and can lead to chronic arthritis. Its symptoms are
Complications
People who have diarrhea symptoms usually recover completely, although their bowel habits may not return to normal until several months later. S. dysenteriae type 1 produces Shiga toxin and can lead to life-threatening hemolytic uremic syndrome (HUS), the same complication that develops in some cases of infection with E. coli bacteria (enterohemorrhagic E. coli or EHEC).
RESEARCH
The National Institute of Allergy and Infectious Diseases (NIAID), is the Federal Government's lead agency for conducting and funding research on many infectious diseases. Scientists at the Institute and NIAID-supported scientists are using basic, clinical, and applied research to better understand how to detect, treat, and prevent foodborne diseases.
Basic research is helping scientists to better understand how pathogens (germs) spread by contaminated food or water cause disease in humans. NIAID-supported researchers are studying the bacterial genes that help pathogens establish themselves in the human body and cause disease. For example, scientists have identified genes that appear to be involved in signaling certain immune system cells to cause inflammation, and which may contribute to the development of diarrhea.
Other NIAID-sponsored research focuses on methods by which the organism grows and interacts in host cells. Scientists have discovered that some intestinal bacteria recognize when they are in a human host and respond by activating a particular set of powerful genes that enable the organism to live in the host and cause disease. Future studies will define new ways to intervene, whether by prevention or treatment, in the disease process.
E. coli
N IAID supports several research studies on E. coli O157:H7 (EHEC). Researchers have sequenced the genome of E. coli O157:H7 (EHEC) and compared it with the genome of the harmless E. coli K12. Seventy percent of the two genomes are identical, and the genome of E. coli O157:H7 is about 30 percent larger than K12. As researchers compare and contrast these and other strains of E. coli, their ability to answer key questions in evolution and disease processes will become easier.
Researchers are working to develop and test monoclonal antibodies to treat EHEC infection, thus preventing hemolytic uremic syndrome (HUS) from developing. (Scientists use monoclonal antibodies as tools for binding to specific protein molecules. As such, they are invaluable in research, medicine, and industry.) Investigators are further defining the ways by which the toxins produced by EHEC and Shigella result in the kidney damage leading to HUS. The primary goal of this research is to better understand how kidney vascular disease progresses. Researchers are developing antitoxins that may help prevent HUS from developing in infected children. Researchers also are exploring vaccines to prevent EHEC and shigella infections in animals or humans.
NIAID-supported scientists found that children with bloody diarrhea should not be treated with antibiotics. Antibiotics can lead to the release of more bacterial toxins and further kidney damage, including subsequent HUS.
The NIAID enteric diseases program also supports basic and clinical research on other water- and foodborne pathogens including Vibrio cholerae, Helicobacter pylori, Yersinia, Listeria, Clostridia, Bacteroides, Staphylococcus and effects of toxins on the intestinal tract.
Cholera
Cholera is a major source of water- and foodborne sickness and death in the developing countries of Asia, Africa, and South America, particularly during epidemics and in refugee settings. Scientific studies have shown that Vibrio cholerae bacteria, which cause cholera, constantly adapt to changes in the environment.
Individual Cholera bacteria can join together to form large mats called biofilms. NIAID-supported scientists recently have sequenced the genome of V. cholerae and have identified a gene family that allows the bacteria to form biofilms. Biofilms protect the bacteria from environmental stresses and make the pathogen more resistant to being disinfected by chlorine. When conditions become favorable, other genes allow the bacteria to revert to their original forms. This is one method V. cholerae uses to survive harsh conditions. Better understanding of how the pathogen can shift will help researchers develop new ways to control it during epidemics.
Other studies on genomes
In addition to the genomic studies mentioned above, scientists have determined the complete genome sequences for Salmonella typhi, S. typhimurium, and Campylobacter jejuni. Sequencing studies are underway for Shigella, Yersinia, as well as other harmful strains of E. coli. Scientists hope this new information will speed the discovery of new targets for treatments and vaccines against foodborne pathogens.
Through preliminary tests of live, attenuated Shigella flexneri vaccine candidates, scientists have discovered two new toxins that may contribute to the diarrhea associated with Shigella species. Studies are under way to find out how these toxins cause fluid loss. The findings will provide crucial information on how to improve attenuated (containing weakened, live virus) vaccines to prevent shigellosis.
Food and Waterborne Diseases Integrated Research Network
NIAID supports the Food and Waterborne Diseases Integrated Research Network to conduct multidisciplinary research and facilitate the development of products to rapidly identify, prevent, and treat food and waterborne diseases that threaten public health. The Network will include Immunology, Microbiology, Zoonoses, and Clinical Research Units. Currently, the Network funds research on
Foodborne viruses
In addition to the organisms mentioned above, NIAID conducts research on foodborne viruses that cause diarrhea such as caliciviruses, rotavirus, astrovirus, and hepatitis A virus. Scientists at the NIAID Laboratory of Infectious Diseases in Bethesda, Maryland, devised the first method for detecting Norwalk virus (a particular calicivirus) particles and for measuring Norwalk virus-specific antibodies. Current studies are trying to produce new vaccines including edible vaccines against Norwalk virus and hepatitis A. NIAID scientists developed a recently licensed inactivated vaccine for hepatitis A virus infection.
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