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129 Cards in this Set

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What bacteria is used to test for fecal contamination
E Coli; it's presence suggests other pathogens may be present
What is an Indicator Microorganism?
A NATURALLY occurring microorganism in food/food processing environment whose presence in indicative of the the occurrence of other organisms or conditions
What criteria should be met in order to use an indicator organism?
-Present and detectable in all foods whose quality is to be assesed
- Easily, Rapidly detectable; can be distinguished from other microbes in the food
- History of constant association with the pathogen; its present when the pathogen is present
- Numbers that correlate with pathogen presence
-growth requirements similar to pathogen
-absence from food free of the pathogen
What is the difference between an indicator and a "surrogate" microorganism?
Surrogate = artificially added
What are categories of indicators?
Indicator Microorganisms
--> can be Safety or Quality
Indicator Metabolites
Name some common Quality Indicator Microorganisms
TPC
Yeasts & Molds
Psychrotrophic bacteria and Thermophillic bacteria
Thermoduric bacteria
--> this is v. broad
What are Safety Indicator Microorganism used to indicate?
Human contamination
Fecal contamination
Pathogen survival and growth
Name three types of Indicator Metabolites
1. Protein and amino acid degradation compounds (cadaverine, putrescine)
2. Organic acids (lactic, propionic, butyric)
3. Volatile compounds (diacetyl in dairy)
Fecal Indicators should also posses what qualities?
-Ideally should only occur in intestine
-should occur in high # in feces
-should posses heat resistance to environment
-detectable at low levels
What are some common fecal indicators?
E.coli (best)
Enterococci
Coliphages
Fecal coliforms (but not so much)
What are some common pathogen indicators?
E.coli for E.coli O157:H7
Listeria spp. for Listeria monocytogenes
Define Pathogen
A microorganism that causes disease and makes people sick
Define Infection
An infection is when the CELL of the microorganism causes the sickness; Some bacteria. If a virus causes sickness, it's by this mechanism (and not intoxication)
What is an outbreak?
Typically 2 or more cases but botulism is the exception - only one case
What is definition of Infection Dose?
The number of cells or virus particles needed to develop symptions
Define incubation time?
The time between the ingestion of food and the time until symptoms develop
What is intoxication?
Example?
Pathogenic cells that produce toxin in food and symptoms develop because of the toxin.
Example: staphoreous infection causes diarrhea and vomiting
What is toxico-infection?
Pathogenic cells that release toxin once they're inside the body; again, the toxin is responsible for the sickness.
What classes of symptoms can develop when infected with a pathogen?
GI -diah., vomit, cramps
or
Systemic - affect other organs (CNS, kidneys, vascular)

Some are accute, some are chronic (cancer from aflotixins, liver damage from hepatitis)
Which are the gram positive pathogens?
vacs By CLaSSes
Bacillus - sporulating rod
Clostridium -sporulating rod
Listeria - rods
Streptococcus -endospore forming cocci
Staphylococcus -ditto
Top 5 baterial causes of illness?
1. Campylobacter (jejuni/coli)
2. Salmonella
3. Clostridium Perfringes
4. Staphylococcus (intoxication)
5. E.coli (toxigenic and other)
Top bacterial causes of death?
Salmonella, Listeria by far (they're also the costliest) Also causes the most outbreaks along with E.coli
What is Toxoplasma gondii?
Particulary lethal parasite that especially affects pregnant women. 375 deaths in 1999.
NOTE: NOT THE MOST COMMON though - most common is giardia lamblia
Most common pathogenic virus?
Norwalk-like virus (also tops in # of deaths)
What does "obligate" mean?
Introduced by human
What is passive vs. active surveilence?
Determines if stool sample test need to be run to check for pathogen.
Salmonella:
Gram stain
shape
O2 requirements
T range
Gram negative
Rod (motile); w/flagella
Facultative anaerobe
Mostly mesophiles, though some can grow at 5 and at 50
What family is Salmonella part of?
Enterobacteriaceae
What was the disease salmonella used to cause? Now?
Typhoid fever; now it's non-typhoid salmonellosis (clever). Cases are rising.
What is the bacteria most commonly implicated in outbreaks?
Salmonell. it accounted for almost 60% of all outbreaks in 2004
What testing is required for salmonella?
Salmonella has a zero-tolerance
What are the most common serovars of Salmonella?
Typhimurium, Enteritidis, Newport and Heildelberg. There are 2463 total serovars.
Other characteristics of Salmonella?
Doesn't ferment lactose, produces H2S, >0.94 awm grows at ph=4; Stress resistant: acid, salt, freezing
What was Leeuwenhook's big contribution to microb?
First to see "little animals" through ingenious device (microscope)
What was Appert's big contribution to microb?
Invented what evolved into the modern-day canning process
What was Koch's big contribution to microb?
He developed the Koch postulates to confirm the infectious nature of disease.
1. Isolate the bacteria from diseased animal
2. Expose a health animal to the bacteria and make it sick
3. Reisolate the baterium form the newly infected animal

Also, the petri dish & use of agar came from his lab
Where was HAACP developed?
Pillsbury
What are the three groups in the "three domain system" of living organisms?
Archaea, Bacteria (both are prokaryotes) and Eukarya
In the "three domain system" which groups contain food borne pathogens?
Bacteria (duh) and Eukarya (molds, yeasts)
How are serovars differentiated?
By the specific antigens that they react with
Name the 6 groups of food microorganisms.
1. Bacteria
2. Yeasts
3. Molds
4. Protozoa
5. Viruses
6. Protozoa
"Eschericia" is what level of taxonimy classification?

Coli?
Enterobacteriacea?
Escherichia: GENERA
Coli: Species
Entero.: Family
Of the 6 groups of food microorganisms, which is the smallest in size?
Bacteria: on the order of 1 micron
How do bacteria reproduce?
Growth by division
What is the compound found in bacterial cell walls?
What are bacterial membranes made of?
Peptidoglycan

Phospholipid bi-layers
What does halotolerant mean?
Capable of surviving high salt concentrations
What is an osmophilic bacteria?
One that is tolerant of high osmotic pressue
Yeast:
Cell size?
Shape?
Reproduction?
2-30 microns (larger than bacteria)
- Unicellular: oval, spherical or elongated
-division or budding
What is the cell wall of
1. Bacteria?
2. Yeast?
3. Mold?
4. Protozoa
5. Viruses
1. peptidoglycan
2. glycans
3. Chitin or cellulose
4. No rigid cell wall
5. Viruses are non cellular!
Cell size of mold?
General structure?
Bigger than bacteria.
20-100 micron.
General structure - filamentous: form hyphae; multicellula
What are "obligate parasites"? Name an example
They cannot live independent of a host - Viruses are an example of an obligate parasite
What is a bacteriophage?
A virus that attacks a bacteria
Name three common food spoilage microbes
Pseudomonas
Lactobacillus
Bacillus
Name three common molds in food
Aspergillus
Fusarium
Penicillum
Name the pathogenic bacteria; which ones are gram positive?
vacs By CLaSSes
One source of microbes in food is epiphytic flora; what is this?
Epiphytic flora are plants that grow attached to host (another plant)
What does CFU stand for?
Colony Forming Units
What is the generation time of a microorganism?
The time it takes to divide in two (or, in other words, to double). "G"; it's related to the specific growth rate, u.
What are the phases in a microbial growth curve?
Lag, exponential (growth), stationary, death
What is the specific growth rate of a microorganism?
It's defined as
'u' in:
N = No* e^(u*t)
In a plot of Ln (N) vs. time (where N = # of microbes), what is the slope?
u the specific growth rate

ln (n/no) = u(t-to)
What is the fastest generation time , g, ever recorded?
8 minutes for clostridium perfringes.
Define:
-Symbiotic growth
-Synergistic growth
-antagonistic growth
-need each other
-complement each other
-kill each other
What is diauxic growth?
Change in growth rate due to change in substrate - cell is busy producing enzymes needed to metabolize new energy source. Cause of "lag" phase.
What is the pH limit of most microbes?

Range of bacteria vs. mold/ yeast?
About pH=4.0; most cannot grow

Molds and yeast can survive at much lower pH - down to 1.5 and 2.0, respectively. All can survive to about ph 8.5-9
Why does low pH inhibit or kill microbes?
Homeostasis must be maintained. The cell expends significant energy to expel H+ ions; the more energy it expends, the less it has for growth.
Why are acids different in their ability to inhibit or kill microbes?
It's related to the hydrophobicity of the organic acid: the more hydrophobic, the easier they can cross the cell's membranes.
Define water activity
aw = %RH
it's the "available" water for microorganisms to grow or rxs to take place
At what aw do microbes no longer grow?
Bacteria vs. yeats/molds?
aw = 0.6
Molds to 0.6
Yeasts to 0.7
Bacteria only .85 and above
What is the oxidation/reduction potential of a food?
It's how oxidized or reduced a food is. If it's more oxidized, there is more O2 around and aerobes will survive.
What condition influence the food Oxidation/Reduction potential?
- packaging: vacuum, gas flush, antioxidants
and!!
presence of -SH reducing groups. (-SH in meat - reacts w/O2 - anaerobes can live)
Why can't anaerobes survive in oxygenated environment?
They don't have the mechanism to dispose of aerobic metabolic waste
What are some natural antimicrobials?
Lysozyme (eggs)
Lactoferrin (Milk)
What are bacteriocins?
Toxins produced by bacteria to kill off other bacteria: a method of competitive exclusion
How does the temperature affect the growth rate of a bactera?
Arrhenius:
Rate=Rateo*e^(-Ea/RT)
But only in range where microbe CAN grow.
What gases have an antimicrobial property?
CO2 and ozone
What is the taxonomy family that encompasses spore-forming bacteria?
Bacillaceae
What are the two most common spore-forming bacteria?
Bacillus and Clostridium
What is an endospore?
A spore formed by a bacteria
What are three very important layers of a spore?
Coats, cortex, core
What is the secret to the durability of a spore?
The cortex - it's the thickest layer of a spore and surrounds the core which contains all the good bits (dna, ribosomes)
What is a spore's cortex comprised of?
Besides peptidoglycan, it contains dipicolinic acid (DPA)which is responsible for much of the spore's resistance
What are some of the reasons spores are able to survive harsh conditions?
Thick cortex layer with DPA/peptidoglycan
-very low moisture content
In what type of foods is inactivation of spores a primary concern?
Low-acid canned foods
What is Pflug famous for?
His work modeling microbial death curve and modeling of spore inactivation.
Are spores metabolically active?
No; they are dormant
Draw the sporeformer cycle; At what stage can toxins be produced?
Toxins can be produced during the sporulation phase;
Vegetative cells->(sporulation) dormant spore->(activation) activated sport->(initiation)germinated spore->(outgrowth) Veg. cell
How do we control spores in food?
Eliminate or removal, inhibition: prevents activation or dormant spores!
What is an endospore?
A spore formed by a bacteria
What is the 'D' value of a spore?
The time required to achieve 90% reduction at T=121C
What are three very important layers of a spore?
Coats, cortex, core
What bacteria have zero tolerance laws?
Listeria monocytogenes
E.coli O157:H7
Enterobacter sakazakii

--> 0/25g
What is the secret to the durability of a spore?
The cortex - it's the thickest layer of a spore and surrounds the core which contains all the good bits (dna, ribosomes)
Why is zero tolerance 0/25g and not just 0?
Limitation in detection
Name some challenges in the microbiological analysis of food
-Complex matrix
-other microorganism
-cells attach to tissue/hard to separate
-food interfers w/analysis (PCR)
-physiological state of microorg (VNC)
-non-homogenous distribution of micro in food
What is a spore's cortex comprised of?
Besides peptidoglycan, it contains dipicolinic acid (DPA)which is responsible for much of the spore's resistance
What microbiological method types can be used for quantitative purposed?
TPC; microscopic methods; and others including physical, biochemical and molecular
What are some of the reasons spores are able to survive harsh conditions?
Thick cortex layer with DPA/peptidoglycan
-very low moisture content
In what type of foods is inactivation of spores a primary concern?
Low-acid canned foods
What is Pflug famous for?
His work modeling microbial death curve and modeling of spore inactivation.
Are spores metabolically active?
No; they are dormant
Draw the sporeformer cycle; At what stage can toxins be produced?
Toxins can be produced during the sporulation phase;
Vegetative cells->(sporulation) dormant spore->(activation) activated sport->(initiation)germinated spore->(outgrowth) Veg. cell
How do we control spores in food?
Eliminate or removal, inhibition: prevents activation or dormant spores!
What is the 'D' value of a spore?
The time required to achieve 90% reduction at T=121C
What bacteria have zero tolerance laws?
Listeria monocytogenes
E.coli O157:H7
Enterobacter sakazakii

--> 0/25g
Why is zero tolerance 0/25g and not just 0?
Limitation in detection
Name some challenges in the microbiological analysis of food
-Complex matrix
-other microorganism
-cells attach to tissue/hard to separate
-food interfers w/analysis (PCR)
-physiological state of microorg (VNC)
-non-homogenous distribution of micro in food
What microbiological method types can be used for quantitative purposed?
TPC; microscopic methods; and others including physical, biochemical and molecular
Salmonella Characteristics?
(gram stain/shape/temperature/spores)
gram negative
facultative anaerobe
rod shaped w/flagella (motile)
mesophilic but some serovars 5, 50ºC
nonsporulating
What family does salmonella belong to?
Enterobacteriaceae
How many sub species of Salmonella are there? How many serovrs?
6 subspecies; ~2500 serovars - most are in subspecies enterica
Name the most common serovars of Salmonella in order and the foods they are found in
Typhemurium - ALL
Enteritidis - Eggs
Newport - ALL
Heidelberg - ALL
Name some differentiating characteristic of Salmonella
- Does not ferment lactose
- Catalase positive
- Produces H2S
- Requires aw.94 and up
- pH 4.0 min growth
- Stress resistant: acid, salt, freezing
Typhoid fever is caused by what serovar?
S. Typhi & S. Paratyphi
Which serovars are responsible for non-typhoid salmonellosis?
All by S. Typhi & S. Paratyphi!! 2400+ serovars cause it! Almost all strains of salmonella are pathogenic
What is the GI disease caused by Salmonellosis called?
Enterocolitis - cramps, diarrhea, nausea, vomiting
Incubation period of Salmonellosis? Infectious dose?
8 -72 hrs (vs. 7 to 28 days w/typhoid fever!)
Dose: 10-10^6
How long does it take for remission of symptoms w/salmonellosis? Is the person "clean" then?
~5 days, but asymptomatic excretion for weeks: they can infect others!
Describe the pathogenesis of Salmonella.
It infects (i.e. the organism is what makes people sick) by invading cells:
1. Attachment
2. Invade
3. Growth, survival
What cells does Salmonella infect?
It invades enterocytes and M cells
"Intracellular" pathogen
List some virulence factors of Salmonella
- appendage proteins
- chaperone proteins
- Type III secretion systems
- Outer membrane secretion channels
- Enterotoxin (acid tolerance response)
- Sideophores
What does commensal mean?
Commensal refers to organisms that live off a host environment but with no ill harm
Top 3 food implicated with Salmonella outbreak?
1. multiple vehicle (could not determine which ingredient)
2. eggs
3. beef
Which foods contain Salmonella most often?
1. Poultry
2. Turkey
3. Beef
4. Pork
--> extremely prevalent in herds - 50-90%
How is salmonella detected?
Very complicated process since there are thousands of serovars which all have slightly different growing requirements
1. homogenization
2. preenrichment (incubate)
3. selective enrichment (3)
4. Plate each of #3 of 3 different media
5. screen in tubes (2 different types)
So for 1 sample = 18 tubes!!
6. Biochem/Serological tests
Principles of Salmonella methods are based on what?
1. Salmonella's ability to reduce S t H2S
2. Salmonella's tolerance to quite a few compounds
3. Alkalinization by lysine decarboxylation
4. Fermentation of xylose and glucose (not lactose)
Is salmonella "emerging"?
No, but some strains are becoming antibiotic resistant
Which serovar(s) of salmonella is antibiotic resistant?
Heidelberg; Newport
Typhimurium DT104 - resistant to 5 antibiotics; epidemic in UK
Biggest Outbreak of Salmonella? Strain?
Eggs - Schwann's. Enteritidis.