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Yersiniosis
Yersinia enterocolitica
Importance
Foodborne yersiniosis was first confirmed in the
U.S.A in 1976 following an outbreak among a large
number of school children from the consumption
of chocolate milk contaminated with Yersinia
enterocolitica. In many other countries, foodborne
yersiniosis was also recorded. In Denmark,
yersiniosis is one of the most common forms of
gastroenteritis.
Yersinia
enterocolitica
was
designated as an emerging foodborne pathogen.
The two most important aspects about the organism
and the disease are that Yersinia enterocolitica is a
psychrotroph and can grow at 0C, and its symptoms
include a sharp abdominal pain with fever,
mimicking an appendicitis.
Characteristics:
Y. Enterocolitica cells are Gram-negative short rods,
nonsporeforming, motile below 37C, and facultative
anaerobic. The strains grow between 0 and 44C,
with an optimum growth at 25-29C. Growth occurs
in milk and raw meat at 1C, but at a slower rate.
Cells can grow in 5% NaCl and at a pH above 4.6.
cells are sensitive to pasteurization.
Habitat
Y. enterocolitica is a normal inhabitant of intestines
of food animals and birds, pets, wild animals, and
humans. Human carriers do not show any disease
symptoms. Different types of food can be
contaminated from these sources.
Toxins
Pathogenic strains are predominant in pigs. The
organism produces a heat-stable toxin, pathogenic
strains carry an invasive factor that enables the cells
to colonize intestinal epithelial cells and lymph
nodes. After colonization the heat-stable toxin
capable of causing the disease.
Disease and Symptoms
Young children are more susceptible to foodborne
yersiniosis. A high dose ( about 10 million cells) is
required for the disease.
Symptoms are severe abdominal pain at the lower
quadrant of the abdomen, diarrhea, nausea,
vomiting, and fever. Symptoms generally appear
24-30 h following consumption of a contaminated
food and last 2-3 days. The disease can be fatal in
rare cases.
Food Association
Because Y. enterocolitica strains are found in the
environment, many foods can harbor the organism.
The organism has been isolated from:
Raw milk, processed dairy products, raw and
improperly cooked meats, fresh vegetables, and
improperly chlorinated water.
Because the cells are heat sensitive, a properly
pasteurized or heated food can have this pathogen
from recontamination following heat treatment. A
food can be contaminated from human carrier or a
pet. As the cells can grow at refrigerated temperature,
even a low initial load can reach a high level during
extended storage of refrigerated foods.
Prevention
Because the strains are psychrotrophic,
refrigeration cannot be used to control their growth.
Good sanitation at all phases of handling and
processing and proper heat treatment are important
to control the occurrence of yersiniosis.
Consumption of raw milk or meat cooked at low
temperature should be avoided.
Listeriosis
Importance
Human listeriosis is caused by Listeria
monocytogenes.
The organism is present in many foods of animal
and plant origin.
Its ability to grow in many foods at refrigerated
temperature helps the organism reach from a low
initial level to an infective dose level during storage
of refrigerated food, which include those that
originally harbored the pathogen and those that
were postheat contaminated.
Any temperature abuse, even for a short time, can
accelerate the growth rate.
Characteristics
L. Monocytogenes is a Gram-positive, psychrotrophic,
facultative anaerobic, nonsporulating, motile, small
rod. In fresh culture, the cells may form short chains. It
is hemolytic and ferments rhamnose.
It grows between 1-44C, with optimum growth at 3537C. It multiplies relatively rapidly at 7-10C. It ferments
glucose without producing gas.
It can grow in many foods and environments.
It is resistant to freezing, drying, high salt, and pH 5.0
and above. It is killed by pasteurization, but when it is
inside white blood cells, a temperature of 76.4-77.8C
for 15 seconds is required to kill the cells.
Habitat
L. monocytogenes is isolated from many environmental
samples: soil, sewage, water, dead vegetation.
It is isolated from the intestinal contents of domesticated
animals and birds.
Humans can carry the organisms in the intestine
Without any symptoms.
A large proportion of uncooked meat, milk, egg, seafoods, as
well as leafy vegetables and tubers(potatoes and radishes)
contain L. monocytogenes.
Many heat- processed foods such as pasteurized milk and
dairy products , and ready to eat meat contain the organism.
The organism is isolated in high frequency from different
places of food processing and storage areas.
Toxin
The virulence factor of L. monocytogenes is a
hemolysin, listeriolysin O. It is produced during the
exponential growth of the cells.
The pathogens invade different body tissues and
multiply inside the body cells, releasing the toxin.
The toxin causes death of the cells.
Disease and Symptoms
People with normal health, following ingestion of a
food contaminated with L. monocytogenes, may or
may not produce symptoms which appear 1-7 days
following ingestion and include mild flu-like symptoms
with slight fever, abdominal cramps and diaarhea. The
symptoms subside in a few days, but the individual
sheds the organism in the feces for some time.
Sensitive groups(pregnant women, unborn fetuses,
infants, elderly and people taking chemotherapy)
show enteric symptoms(nausea, vomiting, diarrhea
and fever).
The pathogen then spreads through the blood
stream and invade tissues in vital organs including
CNS. In pregnant women, the pathogen can invade
fetal tissues through the placenta. Symptoms
include bacteremia, meningitis, endocarditis. The
fatality rate in fetuses, newborn infants and
immunocompromised individuals is very high. The
infective dose is from 100-1000 cells.
Food Association
Consumption of contaminated pasteurized milk, raw
milk, and dairy products, soft cheese, cold cut meats,
improperly cooked chicken.
heat-treated foods were either not properly heated or
were contaminated following heating.
As many raw foods of both animal and plant origin
harbor L. monocytogenes, consumption of raw foods or
recontaminated heat-processed foods has caused
listeriosis.
Growth during long refrigerated storage and
temperature abuse before eating have been implicated
in many cases.
Prevention and Control
Because of ubiquitous presence of L. monocytogenes,
it is impossible to have foods free of this pathogen.
In many countries, a strong listeria control program at
the commercial production facilities has been imposed
by regulatory agencies and industries.
Consumer education to reduce foodborne listeriosis.
This includes thoroughly cooking raw foods of animal
origin; thoroughly washing raw vegetables before
eating; not consuming raw milk or foods made with
raw milk; washing hands, knives. And cutting boards
after handling uncooked foods.
Vibrio parahaemolyticus
gastroenteritis caused by V. parahaemolyticus is
common in japan and accounts for 40-70% of the total
bacterial foodborne diseases.
The high incidence is directly related to the
consumption of raw seafoods.
Characteristics
The cells are Gram-negative, nonsporulating, motile,
curved rods. Catalase and oxidase positive, they
ferment glucose but not lactose or sucrose. They can
grow over a temperature range of 5-42C, with the
optimum 30-37C. The cells multiply rapidly in the
presence of 3-5% NaCl. The cells are extremely
sensitive to drying, pasteurization, refrigeration and
freezing.
Habitat
V. parahaemolyticus strains are halophilic bacteria
distributed in coastal waters worldwide.
They are found in estuarine environment and show
a seasonal variation, being present in the highest
numbers during the summer months.
During the winter months, they remain in the
estuarine bottom on chitinous materials of
plankton.
Toxin
The foodborne pathogenic strains produce a heat-stable
hemolysin and are designated as Kanagawa-positive.
This hemolysin is considered to be the toxin.
The toxin production rate and its level are directly
related to cell growth, cell concentration, and pH of the
environment.
If the toxin forms in food, heating does not destroy it.
Disease and Symptoms
Infectious dose is around one million cells. Symptoms
appear 10-24h following ingestion of live cells and last
for 2-3 days. Symptoms include nausea, vomiting,
abdominal cramps, diarrhea, headache, fever, and chills.
Food Association
Consumption of raw, improperly cooked, or
postheat-contaminated seafoods, including fish,
oysters, crabs, shrimp, and lobster.
V. Parahaemolyticus grow rapidly in unrefrigerated
raw and cooked seafoods and reach an infective
dose level very rapidly.
Many outbreaks in the U.S.A. were identified to be
due to inadequate cooking and crosscontamination of cooked sea foods, followed by
improper holding temperature.
Prevention
No consumption of raw seafoods, proper heat
treatment of seafoods, proper sanitation to avoid
cross-contamination of heated foods,
Proper refrigeration of raw and heated products.
Consumption of food within a reasonable period
of time.
Temperature abuse, even for a short duration, of a
seafood should be avoided.
Enteric Viruses
Unlike bacteria, human enteric viruses do not multiply
in food, some may die off rapidly under various
conditions of food storage and preservation.
Characteristics
Foodborne viral infections can occur only from enteric
pathogenic human viruses.
Hepatitis A, Norwalk-like viruses, Rota viruses have
been associated with foodborne infections.
They are excreted in very high numbers in human
feces. They do not multiply outside human body.
Pasteurization can effectively kill the enteric viruses.
Disease and Symptoms
Enteric viruses can cause infection at a considerably low
dose level.
Following ingestion of hepatitis A viruses through
contaminated food, an individual may or may not develop
symptoms.
In affected individuals, symptoms occur from 2-7 weeks. The
general symptoms are fever, nausea, vomiting, abdominal
discomfort, and inflammation of liver which may follow with
jaundice. Symptoms may last for 1-2 weeks, the viruses are
shed in feces.
NLVs cause gastroenteritis characterized by vomiting and
diarrhea. Symptoms appear 12-24h after ingestion and last
for 1-2 days. The viruses are excreted in feces of infected
persons.
Food Association
Food contaminated with fecal matter of infected
people directly(from food handlers) or indirectly (via
sewage and polluted water) is the main source of both
hepatitis A and NLV outbreaks.
Infected food handlers, even without symptoms, can
contaminate ready-to-eat food with fecal matter.
Vegetables(salads) can be contaminated with polluted
water.
Shellfish harvested from water polluted with sewage
and eaten raw or improperly heated before eating
have been implicated in many outbreaks of both types
of viruses. The virus can survive in shellfish for a long
time.
Prevention
The two major preventative methods of foodborne
virus infections are to kill the viruses in
contaminated foods and adopt good sanitation and
personal hygiene habits to control contamination.
Proper heat treatment, such as pasteurization, is
enough to kill the viruses.
Sanitation using oxidative agents such as
hypochlorite, can kill viruses in contaminated
equipment and in water used for processing.
Vaccination against hepatitis A is available and is
used to control the disease.
Other Foodborne Infections
Brucellosis
Human brucellosis is caused by :
Brucella abortus
Brucella suis
Brucella melitensis
They are Gram-negative, nonmotile, nonsporeforming,
aerobic small rods pathogenic to animals and human.
In infected animals, the organisms are located in the
uterus of pregnant animals and in the mammary glands
of lactating females. Thus, the pathogens can be
excreted in milk.
People working with animals can become infected
with Brucella spp.
People working with meat can be infected.
Consumption of raw milk and products made from
raw milk(e.g cheeses) have been implicated in
foodborne brucellosis.
The cells survive for a long time in milk and milk
products.
Pasteurization kills Brucella cells.
Symptoms of brucellosis in humans include
undulant fever with irregular rise and fall of
temperature, profuse sweats, body aches, aching
joints, chills, and weakness.
Symptoms appear in 3-21 days following
consumption of a contaminated food.
Control measures include pasteurization of milk,
manufacturing of dairy products from pasteurized
milk, and proper sanitation to prevent
recontamination of pasteurized products.
Streptococcus pyogenes
This organism has been isolated from animals with mastitis.
Foodborne infections have been recorded from the
consumption of contaminated raw milk and milk products
made with raw milk and different types of
salads(contaminated by infected food handlers).
Control measures include pasteurization of dairy products and
avoiding the consumption of raw milk and products made
with raw milk.
People who are suffering from streptococcal infections or the
carriers should not handle ready-to-eat foods such as salads.
Proper sanitation in all phases of processing and proper
refrigeration will help reduce the incidence.
Q Fever
Q fever in humans is caused by a rickettsia,
Coxiella burnetii.
Animal carry this organism without symptoms.
People handling animals, raw milk, and meat can be
infected by the rickettsia and develop symptoms of Q
fever.
Symptoms include fever, malaise, anorexia, muscular
pain, and headache. Symptoms appear 2-4weeks after
infection and last for 2 weeks.
Coxiella burnetii is more resistant to heat than many
pathogenic bacteria. Proper pasteurization kills the
bacteria.