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Foodborne disease
Caused by consuming contaminated foods orbeverages.
Poisonous chemicals, or other harmfulsubstances can cause foodborne diseases ifthey are present in food.
Our focus is on those caused by organisms.
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Foodborne disease
More than 250 different foodborne diseaseshave been described.
Most of these diseases are infections, causedby a variety of bacteria, viruses, and parasitesthat can be foodborne.
Other diseases are poisonings, caused byharmful toxins or chemicals
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Campylobacter
causes fever, diarrhea, and abdominal cramps.
The most commonly identified bacterial cause ofdiarrheal illness in the world.
Live in the intestines of healthy birds Most raw poultry meat has Campylobacter on it.
Eating undercookedchicken, or other food thathas been contaminated with juices dripping from
raw chicken is the most frequent source of thisinfection.
Guillain-Barre syndrome can be caused byCampylobacter infection
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Salmonella
is widespread in the intestines of birds, reptilesand mammals.
can spread to humans via a variety of different
foods of animal origin. Salmonellosis, typically includes fever, diarrhea
and abdominal cramps.
In persons with poor underlying health orweakened immune systems, it can invade thebloodstream and cause life-threateninginfections.
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E.Coli O157: H7
has a reservoir in cattle and other similaranimals.
Human illness typically follows consumptionof food or water that has been contaminatedwith microscopic amounts of cow feces.
The illness it causes is often a severe andbloody diarrhea and painful abdominalcramps, without much fever.
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E.Coli O157: H7
In 3% to 5% of cases, a complication calledhemolytic uremic syndrome (HUS) can occurseveral weeks after the initial symptoms.
This severe complication includes temporaryanemia, profuse bleeding, and kidney failure.
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Calicivirus
is an extremely common cause of foodborneillness, though it is rarely diagnosed, becausethe laboratory test is not widely available.
It causes an acute gastrointestinal illness,usually with more vomiting than diarrhea,that resolves within two days.
Unlike many foodborne pathogens that haveanimal reservoirs, it is believed that Norwalk-like viruses spread primarily from oneinfected person to another.
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Calicivirus
Infected kitchen workers can contaminate asalad or sandwich as they prepare it, if theyhave the virus on their hands.
Infected fishermen have contaminatedoysters as they harvested them.
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But facilities available
locally for bacteria. So lets talk more of bacteria that cause
foodborne illness
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Foodborne by direct infectionFoodborne through toxin
Foodborne diseases
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Foodborne through toxin
some foodborne diseases are caused by thepresence of a toxin in the food that wasproduced by a microbe in the food.
For example, the bacterium Staphylococcusaureus
a toxin that causes intense vomiting.
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Foodborne through toxin
The rare but deadly disease botulism occurswhen the bacterium Clostridium botulinumgrows and produces apowerful paralytictoxin in foods.
These toxins can produce illness even if themicrobes that produced them are no longer
there.
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What happens in the body after
the microbes that produceillness are swallowed? After they are swallowed, there is a delay, called
the incubation period, before the symptoms of
illness begin. may range from hours to days, depending on the
organism, and on how many of them wereswallowed.
During the incubation period, the microbes passthrough the stomach into the intestine, attach tothe cells lining the intestinal walls, and begin tomultiply there.
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What happens in the body after
the microbes that produceillness are swallowed?
Some types of microbes stay in the intestine,
some produce a toxin that is absorbed intothe bloodstream, and
some can directly invade the deeper bodytissues.
The symptoms produced depend greatly onthe type of microbe.
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What are foodborne disease
outbreaks and why do they
occur? Occurs when
a group of people consume the samecontaminated food and
two or more of them come down with the sameillness.
It may be a group that ate a meal together somewhere, or
who do not know each other at all, but who allhappened to buy and eat the same contaminateditem from a grocery store or restaurant.
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What are foodborne disease
outbreaks and why do they
occur? For it to occur, something must have
happened to contaminate a batch of food
Often, a combination of events A contaminated food may be left out a room
temperature for many hours, allowing thebacteria to multiply to high numbers, and then be
insufficiently cooked to kill the bacteria.
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How is a foodborne disease
outbreak investigated?
Once an outbreak is strongly suspected, aninvestigation begins.
A search is made for more cases among persons
who may have been exposed. Determined:
The symptoms and time of onset, and location of possible cases is determined, and a "case definition" is developed that describes these
typical cases.
The outbreak is systematically described bytime, place, and person.
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How is a foodborne disease
outbreak investigated?
A graph is drawn of the number of peoplewho fell ill
A map of where the ill people live, work, or
eat. Calculating the distribution of cases by age
and sex shows who is affected.
If the causative microbe is not known,samples of stool or blood are collected fromill people and sent to the public healthlaboratory to make the diagnosis.
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To identify the food or other
source of the outbreak
The investigators first interview a fewpersons with the most typical cases aboutexposures In this way, certain potential exposures may be
excluded while others that are mentionedrepeatedly emerge as possibilities.
Combined with other information, such as
the likely sources for the specific microbeinvolved, these hypotheses are then tested ina formal epidemiologic investigation.
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To identify the food or other
source of the outbreak
The investigators conduct systematicinterviews about a list of possible exposureswith the ill persons, and with a comparable
group people who are not ill. By comparing how often an exposure is
reported by ill people and by well people,investigators can measure the association ofthe exposure with illness.
Using probability statistics, the probability ofno association is directly calculated.
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To identify the food or other
source of the outbreak
Once a food item is statistically implicated inthis manner, further investigation
into its ingredients and
preparation, and
microbiologic culture of leftover ingredients or thefood itself (if available) may provide additional
information about the nature of contamination.
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To identify the food or other
source of the outbreak
Some might think
that the best investigation method would be justto culture all the leftover foods in the kitchen,
and conclude that the one that is positive is theone that caused the outbreak.
can be misleading, because it happens after
the fact.
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Remember
Laboratory testing without epidemiologicinvestigation can lead to the wrongconclusion.
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Even without isolatingmicrobes from food, a well-
conducted epidemiologic
investigation can guide
immediate efforts to control
the outbreak.
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How does food become
contaminated?
Many foodborne microbes are present in healthyanimals (usually in their intestines) raised forfood.
Meat and poultry carcasses can becomecontaminated during slaughter by contact with small amounts of
intestinal contents.
Similarly, fresh fruits and vegetables can becontaminated if they are washed or irrigated with water that is
contaminated with animal manure or human sewage.
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How does food become
contaminated?
Some types of Salmonella can infect a hen's
ovary so that the internal contents of a normal
looking egg can be contaminated with
Salmonella even before the shell in formed.
Oysters and other filter feeding shellfish can
concentrate
Vibrio bacteria that are naturally present in sea water, or other microbes that are present in human sewage
dumped into the sea.
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How does food become
contaminated?
Later in food processing, other foodbornemicrobes can be introduced
from infected humans who handle the food, or
by cross contamination from some other rawagricultural product.
For example, Shigella bacteria, hepatitis A virus and
Norwalk virus can be introduced by the unwashedhands of food handlers who are themselvesinfected.
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How does food become
contaminated?
In the kitchen, microbes can be transferredfrom one food to another food by
using the same knife, cutting board or otherutensil to prepare both without washing thesurface or utensil in between.
A food that is fully cooked can become
recontaminated if it touches other raw foodsor drippings from raw foods that containpathogens.
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How does food become
contaminated?
The way that food is handled after it iscontaminated can also make a difference inwhether or not an outbreak occurs.
Many bacterial microbes need to multiply to alarger number before enough are present infood to cause disease.
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How does food become
contaminated?
Given warm moist conditions and an amplesupply of nutrients, one bacterium thatreproduces by dividing itself every half hourcan produce 17 million progeny in 12 hours.
As a result, lightly contaminated food left outovernight can be highly infectious by the next day.
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Refrigeration or freezing
In general, refrigeration or freezing preventsvirtually all bacteria from growing butgenerally preserves them in a state ofsuspended animation.
This general rule has a few surprisingexceptions.
Two foodborne bacteria, Listeria monocytogenesand Yersinia enterocolitica can actually grow atrefrigerator temperatures.
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High salt, high sugar or high
acid
High salt, high sugar or high acid levels keepbacteria from growing,
which is why salted meats, jam, and pickledvegetables are traditional preserved foods.
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Heat
Microbes are killed by heat.
If food is heated to an internal temperatureabove 160oF, or 78oC, for even a few seconds
sufficient to kill parasites, viruses or bacteria, exceptfor the Clostridium bacteria, which produce a heat-resistant form called a spore.
Clostridium spores are killed only at
temperatures above boiling. This is why canned foods must be cooked to a high
temperature under pressure as part of the canningprocess.
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Heat
The toxins produced by bacteria vary in theirsensitivity to heat.
The staphylococcal toxin which causes vomiting isnot inactivated even if it is boiled.
Fortunately, the potent toxin that causes botulismis completely inactivated by boiling.
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What foods are most associated
with foodborne illness?
Raw foods of animal origin are the most likely to
be contaminated;
raw meat and poultry,
raw eggs,
unpasteurized milk, and
raw shellfish.
Because filter-feeding shellfish strain microbesfrom the sea over many months, they are
particularly likely to be contaminated if there are
any pathogens in the seawater.
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What foods are most associated
with foodborne illness?
Foods that mingle the products of manyindividual animals, are particularly hazardousbecause a pathogen present in any one of theanimals may contaminate the whole batch.
such as bulk raw milk,
pooled raw eggs, or
ground beef,.
A single hamburger may contain meat fromhundreds of animals.
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What foods are most associated
with foodborne illness?
A single restaurant omelet may contain eggsfrom hundreds of chickens.
A glass of raw milk may contain milk fromhundreds of cows.
A broiler chicken carcass can be exposed tothe drippings and juices of many thousands
of other birds that went through the samecold water tank after slaughter.
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What foods are most associated
with foodborne illness?
Fruits and vegetables consumed raw are aparticular concern.
Washing can decrease but not eliminatecontamination.
The quality of the water used for washing andchilling the produce after it is harvested is critical.
Using water that is not clean can contaminatemany boxes of produce.
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What foods are most associated
with foodborne illness?
Fresh manure used to fertilize vegetables canalso contaminate them.
Unpasteurized fruit juice can also becontaminated if there are pathogens in or onthe fruit that is used to make it.
What can consumers do to
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What can consumers do to
protect themselves from
foodborne illness?
COOK
For example, ground beef should be cooked to aninternal temperature of 160o F
SEPARATE
CHILL
CLEAN
REPORT
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Bacteria causing foodborne
infections
Listeria monocytogenes
Salmonella typhi
Nontyphoidal salmonella
Shigella sp. Staphylococcus aureus
Streptococcus group A
Vibrio cholerae, O1 or O139
Vibrio cholerae other serotypes Vibrio parahemolyticus
Vibrio vulnificus
Yersinia enterocolitica
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Emerging diseases: diseases whose incidence has increasedwithin the past 2 decades or threatens to increase in the near
future
Global travel
globalization of foodsupply and centralizedprocessing of foods
population growth andincreased urbanizationand crowding
population movement
due to civil wars,famines and other man-made or naturaldisasters
Irrigation, deforestationand reforestation projectsthat alter habits ofdisease-carrying insects
Increased use ofantimicrobial agents andpesticides, hastening thedevelopment of resistance
Human habits andbehavior
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E. Coli O157:H7
Currently, there are four recognized classes ofenterovirulent E. coli(collectively referred toas the EEC group) that cause gastroenteritis
in humans.
Among these is the enterohemorrhagic(EHEC) strain designated E. coliO157:H7.
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E. Coli O157:H7
E. coliserotype O157:H7 is a rare variety ofE. colithat produces large quantities of one ormore related, potent toxins that cause severe
damage to the lining of the intestine.
These toxins [verotoxin (VT), shiga-like toxin]are closely related or identical to the toxin
produced by Shigella dysenteriae.
http://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm070563.htmhttp://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm070563.htmhttp://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm070563.htmhttp://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm070563.htm7/28/2019 Food Microbiology Lecture Final Pres
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Nature of disease
characterized by severe cramping (abdominalpain) and diarrhea which is initially watery butbecomes grossly bloody.
Occasionally vomiting occurs. Fever is either low-grade or absent.
The illness is usually self-limited and
lasts for an average of 8 days.
Some individuals exhibit watery diarrheaonly.
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Nature of disease
Infective dose -- Unknown,
but from a compilation of outbreak data,
the dose may be similar to that ofShigella spp. (asfew as 10 organisms).
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Course of disease and
Complications
Some victims, particularly the very young,have developed the hemolytic uremicsyndrome (HUS),
characterized by renal failure and hemolyticanemia.
The disease can lead to permanent loss of
kidney function.
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Course of disease and
Complications
In the elderly, thrombotic thrombocytopenicpurpura (TTP). HUS, plus two other symptoms, fever and neurologic
symptoms, constitutes This illness can have a mortality rate in the elderly as
high as 50%.
All people are believed to be susceptible tohemorrhagic colitis,
but young children and the elderly appear toprogress to more serious symptoms morefrequently.
http://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm074156.htm?Purpurahttp://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm074156.htm?Purpura7/28/2019 Food Microbiology Lecture Final Pres
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Associated food
Undercooked or raw hamburger (groundbeef)
Othersimplicated
alfalfa sprouts,
unpasteurized fruit juices,
dry-cured salami, lettuce,
game meat, and cheese curds.
Raw milk was the vehicle in a school outbreakin Canada.
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Diagnosis
Hemorrhagic colitis is diagnosed by isolationofE. coliof serotype O157:H7 or otherverotoxin-producing E. colifrom diarrheal
stools.
Alternatively, the stools can be tested directlyfor the presence of verotoxin.
Confirmation can be obtained by isolation ofE. coliof the same serotype from theincriminated food.
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Food analysis
Unlike typical E. coli, isolates of O157:H7 do not ferment sorbitol and
are negative with the MUG assay;
therefore, these criteria are commonly used forselective isolation.
Sorbitol-MacConkey agar has been usedextensively to isolate this organism from clinical
specimens. Hemorrhagic colitis agar, a selective and
differential medium, is used in a direct platingmethod to isolate O157:H7 from foods.
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Food analysis
A third procedure uses Sorbitol-MacConkeymedium containing potassium tellurite andCefixime.
It includes an enrichment step
Rapid methods using a variety oftechnologies, including recombinant DNA
methods, are being developed.
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Yersinia enterocolitica
a small rod-shaped, Gram-negative bacterium,
is often isolated from clinical specimens such aswounds, feces, sputum and mesenteric lymph
nodes. However, it is not part of the normal human
flora.
Yersiniosis is frequently characterized by such
symptoms as gastroenteritis with diarrhea and/or vomiting;
however, fever and abdominal pain are the hallmarksymptoms.
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Yersinia enterocolitica
Yersinia infections mimic appendicitis andmesenteric lymphadenitis.
Illness onset is usually between 24 and 48hours after ingestion
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Associated food
Strains ofY. enterocolitica can be found in
meats (pork, beef, lamb, etc.),
oysters,
fish, and
raw milk.
The exact cause of the food contamination is
unknown.
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Associated food
However, the prevalence of this organism inthe soil and water and in animals such asbeavers, pigs, and squirrels, offers ample
opportunities for it to enter our food supply.
Poor sanitation and improper sterilizationtechniques by food handlers, including
improper storage, cannot be overlooked.
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Diagnosis
Stool culture is the best way to confirm adiagnosis ofYersinia enterocolitica.
The culture result is usually positive within 2weeks of onset of disease.
Instruct the laboratory to plate entericspecimens onto enteric media, with
incubation at 25C for 48 hours.
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Diagnosis
IfY enterocolitica is suspected, cold enhancement techniques or
cefsulodin-irgasan-novobiocin (CIN) agar should be
used. Colonies deep red center with clear colorless zone, 1-2mm in diameter
Confirmation occurs with the isolation, as well as
biochemical and
serological identification, ofY. enterocolitica from boththe human host and the ingested foodstuff.
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Diagnosis
Presumptive biochemical ID LIA: alkaline/acid(no gas, H2S -negative) Urease -positive
Other biochemical tests: Motility test medium (semisolid)
Y. ent. are motile at 25C (2 left tubes) and non-motile at 35C ( 2 right tubes)
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Diagnosis
Other biochemical tests: Lipase test.
When grown on agar media containing egg yolksuch as Anaerobic egg yolk agar, colonies mayexhibit lipase activity.
A positive reaction is indicated by oily, iridescent,pearl-like colony surrounded by precipitation ring
and outer clearing zone.
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Diagnosis
Identification
use of API 20 E system
Determination of pathogenicity is morecomplex.
presumptive pathogenic Y.enterocolitica
: esculin and salicinnegative
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YERSINIA ENTEROCOLITICA
Pathogenicity testing Pyrazinamidase test(PYZ)*
Congo Red Magnesium Oxalate (CR-MOX)*
Crystal Violet binding Test
Autoagglutination test#
Freezing Cultures#
DNA colony hybridization
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Listeria monocytogenes
a Gram-positive bacterium,
motile by means of flagella.
Some studies suggest that 1-10% of humans
may be intestinal carriers ofL. monocytogenes.
It has been found in at least
37 mammalian species, both domestic and feral,
17 species of birds and possibly some species of fish and shellfish.
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Listeria monocytogenes
some reports suggest that normal, healthypeople are at risk,
although antacids or cimetidine may predispose.
Its ability to grow at temperatures as low as3C permits multiplication in refrigeratedfoods.
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Listeria monocytogenes
has been associated with such foods as raw milk,
supposedly pasteurized fluid milk, cheeses
(particularly soft-ripened varieties), ice cream,
raw vegetables,
fermented raw-meat sausages,
raw and cooked poultry, raw meats (all types), and raw and
smoked fish.
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Listeria monocytogenes
The manifestations of listeriosis include
septicemia,
meningitis (or meningoencephalitis),
encephalitis, and
intrauterine or cervical infections in pregnantwomen,
which may result in spontaneous abortion (2nd/3rdtrimester) or stillbirth.
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Listeria monocytogenes
The infective dose ofL. monocytogenes isunknown but is believed to vary with thestrain and susceptibility of the victim.
From cases contracted through raw orsupposedly pasteurized milk, it is safe toassume that in susceptible persons, fewer
than 1,000 total organisms may causedisease.
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Listeria monocytogenes
Food analysis complex and time consuming Identification based on: Gram stain, gray colonies with halo on PALCAM Hemolysis on BAP, narrow zone of beta hemolysis, Motility-
tumbling motility, end to end with characteristic invertedtest tube brush on semi solid agar
Catalase positive Absence of hydrogen sulfide
Hemolysis by CAMP test using test organisms Blue colonies by Henrys illumination API Listeria Serotyping: 1/2a, 1/2b and 4b commonly reported in
outbreaks
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PALCAM agar
Go to video of tumblingmotility
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Campylobacter jejuni
a Gram-negative slender, curved, and motile rod.
It is a microaerophilic organism, it has a requirement for reduced levels of oxygen.
It is relatively fragile, and sensitive toenvironmental stresses (e.g., 21% oxygen,drying, heating, disinfectants, acidic conditions).
Because of its microaerophilic characteristics theorganism requires 3 to 5% oxygen and 2 to 10% carbon dioxide for optimal growth
conditions.
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Campylobacter jejuni
leading cause of bacterial diarrheal illness inthe United States.
It causes more disease than Shigella spp. and
Salmonella spp. combined.
causes diarrhea, which may be watery orsticky and can contain blood (usually occult)
and fecal leukocytes (white cells).
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Campylobacter jejuni
Other symptoms often present are fever,abdominal pain, nausea, headache andmuscle pain.
The illness usually occurs 2-5 days afteringestion of the contaminated food or water.
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Campylobacter jejuni
The infective dose ofC. jejuniis considered tobe small.
about 400-500 bacteria
in others, greater numbers are required.
The pathogenic mechanisms still notcompletely understood,
but it does produce a heat-labile toxin thatmay cause diarrhea.
may also be an invasive organism.
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Associated foods
frequently contaminates raw chicken. 20 to 100% of retail chickens are contaminated. This is not overly surprising since many healthy
chickens carry these bacteria in their intestinal tracts.
Raw milk is also a source of infections. The bacteria are often carried by healthy cattle
and by flies on farms.
Non-chlorinated water may also be a source of
infections. However, properly cooking chicken, pasteurizing
milk, and chlorinating drinking water will kill thebacteria.
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Recovery from food
Isolation from food is difficult
because the bacteria are usually present in verylow numbers (unlike the case of diarrheal stools).
The methods require an enrichment broth containing antibiotics,
special antibiotic-containing plates and a
microaerophilic atmosphere with 5% oxygen and
an elevated concentration of carbon dioxide (10%).
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Campylobacter jejuni
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Campylobacter jejuni
Other procedures for cheese products available in Bacteriological Analytical Manual (FDA)
l i d
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Isolation procedures
is usually present in high numbers in the
diarrheal stools of individuals,
Cultured on Skirrows medium with vancomycin,
trimethoprim, cephalothin, polymixin andamphoteracin B
Failure to grow at 25C, oxidase positive and
sensitivity to nalidixic acid The optimal temperature for growth is 42C for
C jejuni, and 37C for many of the other entericCampylobacters.
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