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92 Cards in this Set

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Water activity
ratio of the vapor
pressure of the air in equilibrium with a
substance to the vapor pressure of pure
water.
Water activity in food ranges between ...
0 and 1
Moisture content
the amount of moisture
present in the product
Stable, non-perishable foods have a low moisture
content; when subjected to moisture there is a
change in their stability.
Water Activity (aw) equation
aw = p/ps
. Where p = partial pressure of water vapor at the surface
of the product
. ps = saturation pressure
Relative humidity (RH)a
%RH = p/ps x 100
. Where p = partial pressure of the water vapor present in
the gas mixture
. ps = saturation pressurety.
Example values:
aw material
Water,
Sea water
Bread,
Salami
Salted fish
Dried fruit/cereals
1.00 pure water
0.98 sea water
0.95 bread
0.85 salami
0.75 salted fish
0.70 dried fruit, cereals
Different foods are colonized by different
organisms that can...
use its nutrients
. Enteric organisms colonize meats, but rarely fruits
(unless subjected to fecal contamination)
. Pseudomonas, common in water and soil, is found
as a spoilage organism in fresh foods
Microbial Rate of growth on food depends on
Temperature
Nutrient value of the food
Time needed to reach concentration
necessary to cause adverse effects
Size of inoculum
Rate of growth
Processes to slow/prevent the growth of
microorganisms in foods (6)
Temperature
Acidity
Lower water activity
Canning
Chemicals
Irradiation
Temperature has what effect on microorganisms?
Lower storage temperature = slower growth
cold tolerant; grows at refrigeration
temperature known as ...
Psychrotolerant
Acidity has what effect on microorganisms? (what pH below?)
Acid used to �pickle� food. pH 5 = inhibit spoilage Stop organisms metabolism.
Lower the water activity: Three ways:
Add salt.
Add sugar.
Drying/lyophilization (freeze drying).
Canning has what effect on microorganisms?
Placing foods in jars or cans and heating them to a
temperature that destroys microorganisms. During heating air is driven out of the jar and as it
cools a vacuum seal is formed
. Vacuum seal prevents air from entering product
bringing with it contaminating microorganisms
. Stored in absence of refrigeration
Two safe processes for canning food: (which is better and why?)
the boiling water bath method
and the pressure canner method.

Pressure canner method is best (boiling can method may allow anaerobic orgs to survive: i.e. botulism and/or toxin)
Antimicrobial Chemicals do what for food:
Inhibit microorganism growth. Preservatives. Examples: Sodium/Ca propionate, Na benzoate.
FDA GRAS stands for
Food and Drug administration: Generally recognized as safe.
Irradiation is/does
controled doses of gamma rays. Destroys organism DNA (irreparable). Used on packaged or canned food.
Foodborne disease categories (how the diseases are released): (3)
Biomisfortune (? = third side)
Biocrime/biomisdemeanors(?)
Bioterror/Biowarfare
Biomisfortune
. Naturally occurring foodborne disease
. Virtually all foodborne disease falls in this
category
. A daily concern of public health departments
Foodborne Disease Types
2. Biocrime and biomisdemeanors
. Intent to harm for personal gain or revenge
. A few dozen events in recent decades
3. Bioterror and biowarfare
. State-sponsored or hate group terrorism
Microorganisms can cause disease in three ways:
Toxins from plants/alge/fungus.
Microbial infection.
Bacterial toxins. (examples: third side)
Mushrooms �V amanitas type (1-2 bites can be
fatal to an adult)
�� Water hemlock �V most toxic of all North
American plants; Cicutoxin - no antidote,
death in 30% of reported poisonings
�� Castor bean �V ricin toxin (Select Agent)
�� Jimsonweed �V poisonous seeds, leaves and
nectar
Ergot - mold infects grain
�� Aflatoxin - toxin produced by mold growing
on nuts and grains; potent carcinogen
�� Certain fish and shellfish
. Ciguatoxin: reef and rocky bottom fish, algal toxin
. Scombroid poisoning: deep sea fish, bacterial toxin
. Paralytic shellfish poisoning: shellfish, algal toxin
2. Microbial infection
e.g., brucellosis, Campylobacter enteritis ,
listeriosis, salmonellosis, toxoplasmosis,
trichinellosis, infection with vibrios, E. coli ,
hepatitis A, shigellosis, viral gastroenteritis
3. Bacterial toxins
. produced in the food before consumption
e.g., Clostridium botulinum, Staphylococcus
aureus
. produced in the intestines
e.g., Clostridium perfringens
Food poisoning is otherwise known as ... and is ..
Food poisoning (food intoxication)
. toxin produced by microorganism in food
. toxin ingested
Food infection
microorganism ingested and reproduces in host
Food intoxication
The microorganisms grow in food and
produce toxin
�� Do not necessarily grow in the host and may
not be alive when the food is ingested
�� Preformed bioactive toxin
�� Important Bacterial Intoxications
. Staphylococcus aureus �V enterotoxin in food not
destroyed with cooking
. Clostridium botulinum - produces deadly
neurotoxin (heat labile)�
Staphlococcus aureus:
Signs/symptoms
Virulence factors do ...
Dx, Tx, prevention:
Signs and symptoms
. Nausea, vomiting, diarrhea, cramping
. Pathogen and virulence factors
. Caused by Staphylococcus aureus
. Virulence factors include five enterotoxins
. Pathogenesis and epidemiology
. Outbreaks associated with social functions
. Diagnosis, treatment, and prevention
. Diagnosis based on signs and symptoms
. Treatment based on fluid and electrolyte
replacement
. Proper hygiene can reduce incidence
S. aureus transmission
�� Reservoir
. Humans �V approx. 25% - 35% of healthy individuals
are carriers of S. aureus
. Occasionally cows, dogs, fowl
�� Transmission
. Foods that come in contact with food handler��s
hands
�G Without subsequent cooking
�G Inadequate heating or refrigeration
S. aureus: general info:
Gram-positive cocci, arranged in clusters
�� Non-motile
�� Facultative
�� Tolerate drying, high salt (low aw)
�� Often pigmented c=
S. aureus: percent of intoxication cases US:
Sources:
Onset of symptoms time:
�� 20-40% of all food intoxication cases
(est.185,000 cases/yr in U.S.)
WHAT WENT WRONG? (third side)
�� sources
. cream pies
. sauces
. gravies
. cooked ham
. chicken/egg salad
. pastries
. food held at improper temperature
�� onset of symptoms
. 2-4 hrs avg.
. early as 30 min
These foods are often kept at room
temperature or outdoors at picnics
�� Staphylococcus , if present as a contaminant,
proliferates, producing enterotoxins
�� Refrigeration slows growth of Staphylococcus
�� Toxins are relatively heat stable
. several stable at the boiling point
. re-heating food not effective
S. aureus: Enterotixins (5 sort of).
Seven different toxins
. A, B, C1, C2, C3, D, and E
. A - most often implicated in foodborne
intoxication
. Stimulates T cells that release cytokines,
activating a general inflammatory response in
the intestine leading to gastroenteritis with
massive fluid loss from the intestine
ONSET (third side)
ILLNESS, Severe
Tx
Short period before symptoms �V range 30
min to 6 hrs (Why?)
�� Illness can be severe
. Profuse vomiting (may have blood)
. Nausea
. Abdominal cramps
. Diarrhea (may have blood)
�� Self-limiting, resolves 48 hours after onset
�� May require treatment for dehydration
�� Antibiotic treatment not useful (Why not?)
S. aureus: Dx
Illness usually self-limiting; hospitalization
rare
�� Diagnosis in outbreak settings
. Culture of S. aureus 105/g of food
. Detection of enterotoxin
�� Absence of culturable staphylococci does not
rule out diagnosis
�� Diagnosis can be confirmed by isolation of
same species type from human stool
�� Typing, enterotoxin tests not routinely
available
S. aureus: Control measures
Educate food handlers
. Food hygiene
. Dangers of working with exposed skin, nose or eye
infections, and uncovered wounds
. Reduce educe food handling times (4 hr max),
store/cook at proper temperatures
. Exclude workers with infections of hands,
face or nose
. Discard food if kept above 4��C for > 2hrs
C. botulinum: about
how may/year US (%mortality)
Anaerobic, gram positive endosporeproducing
bacilli
�� Common inhabitants in soils
�� Endospores are heat stable
��Spores germinate and toxin is produced.

Approx. 50 cases/yr in US
. ~25% fatal
Botulism is ...
Signs/symptoms ...
causitive agent (and spelling!)
Signs and symptoms
. Caused by intoxication from ingested toxin
. Three primary forms
. Food-borne botulism . progressive paralysis of all
voluntary muscles
Botulism
. Infant botulism . bacteria grow in the intestines,
producing non-specific symptoms
. Wound botulism . symptoms like those of food-borne
botulism
. Pathogen and virulence factors
. Clostridium botulinum is the causative agent
. Different strains produce one of seven neurotoxins
. Four types cause human illness
Botulism:
epidemiology ...
Most commonly affects ...
Dx, Tx, prevention ...
Epidemiology
. Rare, roughly 50 cases of food-borne and wound
botulism per year in U.S.
. Infant botulism most common form in U.S.
. Diagnosis, treatment and prevention
. Diagnosis . flaccid paralysis, neurological symptoms
Botulism
. Three approaches to treatment
. Washing of intestinal tract to remove Clostridium
. Administration of botulism immune globulin
. Treatment with antimicrobial drugs
. Prevention - destroying endospores in contaminated
food through proper canning techniques�
Botulism toxin:
LD50 ...
Does ...
One of the most lethal substances known
�� Lethal dose (LD50) = 1ng/kg of body mass��

Inhibits ACH production at neuronal cleft.
Botulism affects ______ (human sub-population)
Through ingestion of ____ (food product) which contains ____ (organism/state). Prevent by ____.
infants
Honey (or improperly canned foods)
C. botulinum (spores)
Prevent by waiting until infant gut flora sufficient to fend off organism (~6 mo.)
C. perfringens
Food Intoxication:
Dose ...
Commonly found in what foods ...
Why?
Disease caused by ingestion of large dose
. >105 cells
Contaminated and inadequately cooked foods

C. perfringens .
Food
Intoxication
. Meats, esp. cooked in bulk
. Poultry
. Fish
. Insufficient heating and then holding at 20-40��C
. Organisms present, but no toxin yet

ONSET (THIRD SIDE)
7-15 hours after consumption
. Cells begin to sporulate in the intestine
. Triggers production of toxin
. Alters permeability of epithelium
. Results in diarrhea and cramps
. NO vomiting, NO fever
. Symptoms resolve within 24 hours; self-limiting
. Rarely fatal
C. perfringens
When seen (time of year) ...
Pre-cooked food is dangerous because ...
Often seen in the fall and winter months
�� Institutions and large gatherings with large
scale meat cooking
�� High attack rate
�� Also demonstrated when food is pre-cooked
and then re-heated
. spores resist first heating, germinate in the food
and proliferate, second heating is inadequate, cells
are ingested �V sporulate in intestine, produce toxin
. Ex) baked potatoes wrapped in foil re-heated the
next day caused outbreak �V food chainp >
C. perfringens commonly found in ... (3)
Common in soil
�� Also lives in the intestinal tract of many
animals
. found in sewage
�� May contaminate food products at harvest
and at preparation
. Agricultural practices
. Food handlers
C. perfringens Dx
Isolating C. perfringens from anaerobic
cultures of food or stool
�� Demonstrating toxin in stool
�� No treatment is usually given
Food infection definition
Active infections resulting from ingestion of
food with microbial contaminants present
�� May or may not have a toxin componentiven9AD
Campylobacter - Diarrhea
Caused by ...
about org ...
Pathogenisis/epidemiology ..
Dx, Tx, prevention ...
Pathogen and virulence factors
. Caused by Campylobacter jejuni
. Gram negative rod-shaped bacterium
. Virulence factors include adhesins, cytotoxins,
endotoxin

Campylobacter Diarrhea
. Pathogenesis and epidemiology
. Virulence factors produce bleeding lesions and
trigger inflammation
. Diagnosis, treatment, and prevention
. Diagnosis based on signs and symptoms
. Most cases resolve without treatment
. Proper hygiene after handling raw poultry
Campylobacter is the ___ type of food infection.
Typically found in _____ (5)
Onset of symptoms ...
___% develop long term problems/complications.
most common bacterial food infection
�� sources
. undercooked chicken/turkey/pork
. unpasteurized milk
. raw clams
�� 1-10 days (3-5 avg.) for onset of
symptoms
�� up to 10% may develop serious, longterm
complications
E. coli 0157:H7:
Normal flora of ...
Found in (3).
Effective dose is (low, really low, high, really high)?
Produces ___ toxin.
Onset of symptoms is ...
~# cases / deaths/yr
normal flora of healthy cattle
�� sources
. undercooked beef
. unpasteurized fruit juice
. sprouts
�� LOW infective dose, produces verotoxin
(shiga-like toxin)
�� 1-10 days to onset of symptoms
�� 60,000 cases with 50 deaths/yr
E. coli 0157:H7:
Known as ...
Causes ...
It is treated by ...
complicatons (2) ...
Disease
. Hamburger disease: bloody diarrhea (hemorrhagic
colitis)
. Self-limiting; 8 days average
. Complications
. Hemolytic-uremic syndrome, a blood and kidney
disease in children
. Thrombotic thrombocytic purpura, a dire disease in
the elderly
E. coli 0157:H7:
Dx
Tx ...
�� Diagnosis - E. coli 0157:H7
. Culture stool samples
. Testing for the toxin produced by the bacteria.
�� Treatment
. Fluid replacement
. Physician, hospital care�ұ�]�
Listeriosis, caused by ...
about ...
commonly found in what foods ...
Onset ...
Cases/yr ...
~mortality and rate ...
Listeria monocytogenes
Gram-positive, motile . flagella
. psychrophile
. Food sources
. soft cheeses
. cold cuts
Listeriosis
. hot dogs
. milk
. raw meats and fish
. 4 days - weeks to onset of symptoms
. 2,500 cases/yr
. 500 deaths (20% death rate)ase
Listeriosis,
signs/symptoms ...
Infective dose ...
pathopsysiology ...
Very dangerous for which group ...
Signs and symptoms
. Influenza-like symptoms
. Fever
. GI symptoms . nausea, vomiting, diarrhea
. Infective dose - < 1000 cells
. Invades GI epithelium
. Enters host monocytes, macrophages, leukocytes
. Septicemia (50% mortality)
. Meningitis (70% mort.), encephalitis
. Pregnant women/fetus (80% mort.) at risk
Listeriosis,
Dx ...
Detection (in food) ...
Tx ...
Diagnosis
. Culturing L. monocytogenes from blood,
cerobrospinal fuid, placenta
. Food analysis
. Culture
. 5-7 days
. No DNA detection methods yet
. Treatment
. Antibiotics . e.g., penicillin, ampicillin\
Shigellosis:
Caused by (4) ...
About ...
Pathogenisis/epidemiology
Dx, Tx, prevention ...
�� Pathogen and virulence factors
. Caused by Shigella dysenteriae, S. flexneri, S. boydii, and
S. sonnei
. Gram negative bacteria
. Virulence factors include enterotoxins such as shiga toxin
�� Pathogenesis and epidemiology
Shigellosis
. Pathogen colonizes cells of the small, then large intestine
. Incubation 1-3 days
. Dysentery or watery diarrhea, fever, nausea
�� Diagnosis, treatment, and prevention
. Diagnosis based on symptoms and presence of Shigella in
stool
. Supportive treatment and administration of antimicrobials
Shigellosis:
Pathophysiology ...
Sigella attaches to epitheilal cell of colon. Triggers endocytosis (goes into cell). Sigella multiplies in cytosol. Invades neighborinig epitheial cells, thus avoiding immune defenses. Forms mucosial absesses, and kills cells. Shigella enters blood stream, and is quickly phagocytised and destroyed.
Salmonellosis:
Causative agent ...
Commonly found in which foods (5) ...
Onset ...
Small fraction of those infected may develop ...
�� Salmonella spp.
�� Gram negative bacterium
�� sources
. poultry
. meat
. eggs
. sprouts
. un-cracked eggs shells (1 in 10,000 contaminated)
�� 12-24 hrs for onset of symptoms (18 hrs avg.)
�� some remain carriers for months
�� small percentage may develop serious chronic
disorders.) at risk
Salmonellosis:
Pathopysiology ...
Salmonella attaches to epitheial cells lining the sm. intestine.
Triggers endocytosis.
Salmonella multiplies inside vesicles.
Kills host cells, indusing cramps, fever and diarrhea.
Bacteriemia if Salmonella moves to blood stream (typhi).
Phagocytised, but not destroyed.
Goes to blood centers (next question).
Shed in feces.
Salmonella can affect these body parts:
Liver
spleen
bone marrow
gallbladder (basically anywhere blood can go in large quantities, with the exception of the gall bladder ... you just have to remember that).
Typhoid fever:
causitive agent
Symptoms ...
Treatment ...
Occurance ...
Dx....
Infectious agent - Salmonella typhi
�� Symptoms - diarrhea, systemic disease, and a rash
�� Treatment (2-4 weeks)
. Fluids and electrolytes intravenously
. antibiotics
�� Occurrence - common in developing countries, but
fewer than 400 cases in the U.S. each year
�� Diagnosis
. Blood culture
. Stool culture
. ELISA urine test
E. coli Description
�� Gram-negative bacillus (1.1-1.5 �gm x 2-6
�gm)
�� Motile, non-endospore former, facultative
�� Growth range of 15-45�XC
�� Optimal growth at 37�XC
�� generation time = doubling time = 20 min
�� best temperature for production of toxins
E. coli: Commonly resides in ...
Enteric bacterium
�� Normal flora inhabitant of the intestine of
humans, mammals, and birds
�� No normal presence in environment
�� Excreted in the feces (106-107/g)
�� ~200 known pathogenic E. coli
�� cause life-threatening diarrheal and urinary
tract disease
E coli: Antigens (5)
Traditionally characterized by their surface
antigens
�� O = long polysaccharide chains of the LPS
�� H = flagellar proteins (if motile)
�� These antigens resulted in classification of
serotypes
�� numerous different O antigens (numbered 1-181;
some now excluded, some identical)
�� H may or may not be present (must have flagella;
numbered 1-56; really only 53)
�� Also K (heat sensitivity) and F (fimbrial)antigens
Six major categories of E. coli strains cause
enteric disease
�� Enterohemorrhagic
�� Enterotoxigenic
�� Enteroinvasive
�� Enteropathogenic
�� Enteroaggregative
�� Diffuse-adherence
�� All share adherence as a virulence mechanism
Enterohemorrhagic strains (3)
�� Shiga toxin-producing E. coli (STEC)
�� E. coli 0157:H7 most common STEC
serotype in North America
�� Verotoxin producing E. coli (VTEC)
�� Enterohemorrhagic E. coli (EHEC)
Enterohemorrhagic E. coli (EHEC)
�� Only pathogenic E. coli that has a
definite zoonotic origin
�� Reservoir �V cattle, other ruminants
�� Occurrence �V North America, Europe,
Japan, South America, South Africa
�� Transmission �V food contaminated
with ruminant feces
�� Most common cause of kidney failure
in children
Enterohemorrhagic E. coli (EHEC) Pathophysiology
Following ingestion organism grows in
the small intestine
�� Produces Shiga toxin - a potent
cytotoxin that inhibits protein
synthesis within eukaryotic cells
�� Causes bloody diarrhea and kidney
failure
STEC
Now recognized that over 200 serotypes
associated with Shiga toxin (6 important
serogroups, e.g. 0157)
�� Shiga toxin Stx 1 and Stx 2 are also called
�� Verocytotoxin
�� Verotoxin
�� Shiga-like toxins
�� Predominant serotype O157:H7
�� Bloody diarrhea in all age groups
�� Young children - may lead to hemolytic-uremic
syndrome (HUS), kidney disease
�� O157:H7 causes 90% of HUS in N.A., 50% in Germanyria
STEC:
Infectious dose ...
% resistant to antibiotics ...
fatality percent ...
Infectious dose <100 cells, but
people can carry the organism as
transient gut flora w/o disease.
�� ~ 20% of O157 isolates resistant to
antibiotics
�� 5-10% of cases have fatal
complications
STEC: Toxin pathophysiology
Toxin production is a prerequisite to
disease
�� Toxin passes through intestinal
epithelium to reach the endothelial
cells lining the small blood vessels
that supply the
�� Gut
�� Kidney
�� Other viscera
STEC: Survival outside of host ...
Survival
�� Well adapted to survival in animal feces
�� Several weeks to months
�� Temperature and water activity dependent
�� Lab study - spiked feces survival >70 days
at 5�XC, 0.98 aw
�� Surface of grazing land - decrease from 108
CFU/g to 105 CFU/g within 50 days, but still
detectable for up to 99 days}
STEC Transmission via food
Transmission via foods
�� Main - bovine origin
�� beef (mass produced ground
Milkborne outbreaks
�� 1994 - UK milk sold as pasteurized
�� 100 affected
�� ~1/3 hospitalized; 9 with HUS
�� 1999 largest milkborne outbreak in the
UK
�� 144 cases; 32% admitted to hospital with
HUSscerabeef)Transmission via foods
�� Others �V foods fertilized with manure
�� Fruits
�� Unpasteurized fruit juice
�X Apple cider
�� Potatoes
�� Fresh vegetables eaten raw
�� sprouts, lettuce, tomatoes
�� raw milk (but only <1% - 3% of samples
positive)
�� Recent outbreaks
�� Low pH foods
�� Fermented salami
�� Mayonnaise
�� Yogurte
STEC: Direct person to person ... senerio.
Rate of disease, US ...
Direct person-to-person (day care
facilities)
�� Long term shedding in 13% of patients despite
clinical care
�� CDC - STEC cause approximately
100,000 illnesses, 3,000
hospitalizations, and 90 deaths
annually in the U.S.
STEC Control Strategies
Improved cattle herd management to limit prevalence of
carriers
�� Minimize slaughterhouse contamination of meat by
animal feces
�� Decrease fecal contamination of foods consumed raw;
fertilizing with animal waste
�� Pasteurize dairy products
�� Wash fruits and vegetables, peel
�� Wash hands
�� Cook beef adequately (70oC)
�� Ensure hygiene in childcare centers�
Enterotoxigenic E. coli (ETEC): causes diseases in ...
�� 75% of traveler��s diarrhea cases
�� Infants and children in developing countries
�� 380,000 deaths annually in children < 5 yrs.
�� Adhere to mucosa of small intestine, but do not
invade
�� One heat-labile and two heat-stable enterotoxins
�� To cause disease must colonize and produce
toxins�
Enterotoxigenic E. coli (ETEC) Transmission
�contaminated food and
water
�� Lettuce in salads
�� Fresh vegetables
�� Water
�� Soft cheeses (brie and camembert): >3000 cases in U.S. in
1983
�� Infection rate in Mexico for visitors = 50%
�� Not a problem for residents in Mexico
�� Chronic exposure resulting in production of
secretory antibodies present in the bowel
�� May prevent successful colonization of the
pathogen
Enteroinvasive E. coli (EIEC);
Affects ...
Signs ...
Where in world found ...
Reservoir ...
Transmission ...
�� Invasive disease in the colon �V all age
groups
�� Water and bloody diarrhea
�� Developing countries
�� Reservoir �V humans
�� Transmission �V contaminated food
�� In 1997, 387 cases in U.S. due to
imported soft cheeses (brie,
camembert, coulommiers)ithin 50
Enteropathogenic E. coli (EPEC) ... describe.
�� Oldest recognized category
�� Most frequent cause of diarrhea in infants
in developing countries; most cases in first
3 years of life
�� No invasive disease
�� No toxin production
�� Transmission �V contaminated formula and
weaning foods
Enteroaggretive E. coli (EAEC): Describe ...
�� Diarrhea-causing pathogen, or only
some strains?
�� Developing countries
�� Adhere to enterocytes, form thick film
of aggregating cells and mucus
�� 10-20% of traveler��s diarrhea
Hepatitis A virus
Food sources ...
Onset of symptoms ...
Infection persists for ...
Food sources (also transmitted
person-to-person)
�� raw clams or oysters
�� seen in glazed doughnuts, orange
juice, salads
�� onset of symptoms
�� 10-50 days following ingestion
�� most contagious 10-14 days BEFORE
symptoms
�� infection persists for weeks-months
�� some may lead to liver damage?�
Hepatitis A virus
Symptoms ...
Rates U.S. ...
Symptoms
�� Fever
�� Nausea, vomiting
�� Abdominal, joint pain
�� Dark urine
�� Jaundice
�� Decreasing in the U.S.
�� 25,000 cases in 2007
�� Vaccine introduced in 1995
�� Children, travelers, at risk population/
Norovirus
about ...
Single-stranded RNA, non-enveloped
virus
�� Caliciviridae family
�� Norovirus official genus name
(previously described as ��Norwalk-like
viruses��)
�� Five groups, three affect humans
�� Up to 30% of infections asymptomatic
(CDC, 2010)m�
Norovirus:
Causes ...
% of gastroentitis ...
Environmetal exposure ...
More cases of acute gastroenteritis than
any other foodborne pathogen (~21
million/yr)
�� Nearly 60% percent of estimated
illnesses, but a much smaller proportion
of severe illness, caused by norovirus
�� Highly contagious
�� Environmental persistence
�� Difficult to control with routine
sanitation�?�
Norovirus:Illness
Incubation ...
lasts ...
Characterized by s/s ...
Treatment ...
Increased risk of complications to which groups? Why?
�� Incubation period is 12-48 hours
�� Illness lasts 12-60 hours
�� Self-limiting
�� Increased risk for complications because of
volume depletion and electrolyte
disturbances
�� Elderly
�� Children
�� Severe underlying medical conditions
�� Hospitalization of adults who are otherwise
healthy is rare
�� Neither specific antiviral treatment nor a
vaccine has been developed for noroviruses
�� Characterized by sudden onset of
�� Nausea
�� Vomiting
�� Watery diarrhea( �(
Norovirus:
Where outbreaks occur (4) with percentages ...
Of 660 outbreaks confirmed by CDC
between 1994 and 2006,
�� 36% were from long-term care facilities
(e.g., nursing homes),
�� 31% were from restaurants, parties, and
events,
�� 20% were from vacation settings
(including cruise ships), and
�� 13% were from schools and community
settings
CDC Vessel Sanitation Program ... Mission:
�� Established early 1970s
�� Mission:
�� inspecting cruise ships (periodic and
unannounced)
�� monitoring gastrointestinal illnesses and
investigating or responding to outbreaks
on cruise ships .13 passengers with
foreign itineraries sailing into U.S. ports
�� training cruise ship employees on public
health practices.

providing health education and reliable
and current public health information to
the cruise ship industry, the traveling
public, public health professionals, state
and local health authorities, and the
media
Mad Cow Disease
Bovine spongiform encephalopathy (BSE)
�� 1986 �V new animal illness in U.K.
�� slow-progressing neurological infection, cattle
stagger/collapse
�� sponge-like h sponge holes in brains of animals
�� 1989 �V USDA imposed ban on imports of live
cattle, sheep, and derived products from the
U.K. and countries with BSE outbreaks
�� 1990 �V USDA surveillance to detect BSEaffected
cows

addition of rendered meat-and-bone meal
to livestock feed as (cheap) dietary
supplement
�� scrapie-infected sheep carcasses in mix;
cost-cuts to use lower cooking temp.
�� low rendering temperatures failed to
inactivate previously unrecognized
infectious proteins (prions)
�� 1997 �V bans on use of animal protein in
cattle feed
�� 2003 �V first case in U.S.ters�
Spongiform Encephalopathies
Types (2) ...
Number of cases in 2004 ...
Creutzfeldt-Jakob Disease (CJD) �V rare, fatal,
human disease
�� 1996 �V U.K., link between CJD and people who
ate BSE-contaminated meat
�� Variant CJD (vCJD) acquired by diet
�� 153 cases worldwide as of 2004
�� ��species jump�� of pathogenic prions
�� Prions �V abnormally folded prion protein
�� Definition �V infectious proteinaceous particle�
Spongiform Encephalopathies:
Incubation period ...
Symptoms/signs ...
Incubation period measured in years
� Illness lasts 13-14 months
� When prions hit a critical level in the
brain, symptoms progress very quickly
� Neurologic abnormalities
� Ataxia � unsteadiness due to disease in
brain tissue
� Dementia � loss of memory and confusion
� Myoclonus � abnormal contraction of
muscles later in the illness
� Immobility
� Muteness
� Death
Food Microbiology
Difficulties ...
Solutions. ...
Difficulties
�� microbiological analyses are destructive
�� 100% inspection is impossible
�� consumer cannot be 100% protected
�� length of many conventional analyses
�� perishables released/consumed before completion of
analysis

Solutions
�� end-product analyses performed as part of QA
plan
�� representative sampling allows acceptance or
rejection of batch based on samples collected
�� rapid methods provide results in a few hoursdia
Food Microbiology
Sampling and Investigation
Methods
�� collection of large/representative food
samples
�� batches in packets, cans, bags,
containers �V individual testing of a
number of units selected at random
�� package food products
�� package opened only in the laboratory
�� sampling performed aseptically
�� sampling tools �V wrapped and sterilized
Food Microbiology
Sampling and Investigation
Methods:
Liquids ...
Examples: milk, ice-cream mix, sugar
syrups
�� Representative sample
�� mixed thoroughly up and down (e.g., sterile
ladle)
�� 100-500 ml dispensed into sterile container
�� transported to the laboratory (transport
temp.)
�� in the lab., mixed again before analysis
Food Microbiology
Sampling and Investigation
Methods:Solid samples ...
May be performed using sterile scalpels,
spoons or cork-borers
�� Particulate food (e.g., flour, dried milk)
should be mixed, and approx. 100 g
collected
�� Bulk products
�� larger samples from more than one
location should be collected
�� mixed and analyzed separatelyomm
Food Microbiology
Sampling and Investigation
Methods: Meat, fish, and similar foods
�� collect deep and surface samples
�� careful collection of deep samples to
minimize contamination from surface
�� foodstuffs such as fresh and cooked
meats �V sampled using sterile carving
knife, scalpel, forceps
�� frozen foods �V cork-borer or electric drill
(bore-extracting bit) used to obtain
deep samples without thawing
�� surface slices �V thin slices of superficial layers,
homogenize (with diluent), plate
�� rinses and washes �V agitate in sterile diluent
�� sausages, dried fruits, vegetables
�� swabs �V use sterile template for quant. results
�� adhesive tape �V pressed against
food/equipment surface, pressed onto suitable
culture medium
�� contact plates�]�
Food Microbiology
Sampling and Investigation
Methods: Transport and Storage
�� frozen foods - kept frozen until
analysis
�� perishable (unfrozen) foods
�� refrigerate until tested
�� refrigeration for �d3 days will result in
microbial amplification, and may cause
death of certain microorganisms
�� record sampling, transport, and
storage conditions
Facts about food storage:
 > 54 billion meals are served at 844,000
commercial food establishments in the US/yr
 46% of the money Americans spend on food
goes for restaurant meals
 On a typical day, 44% of adults in the United
States eat at a restaurant
 A mean of 550 foodborne disease outbreaks
per year reported to the CDC from 1993
through 1997
 >40% were attributed to commercial food
establishments
Top ten risiest foods: Food, #outbreaks, #cases of illness.
Product # of outbreaks Reported cases of
illness
LEAFY GREENS 363, 13,568
EGGS 352, 11,163
TUNA 268, 2,341
OYSTERS 132, 3,409
POTATOES 108, 3,659
CHEESE 83, 2,761
ICE CREAM 74, 2,594
TOMATOES 31, 3,292
SPROUTS 31, 2,022
BERRIES 25, 3,397