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129 Cards in this Set
- Front
- Back
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What bacteria is used to test for fecal contamination
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E Coli; it's presence suggests other pathogens may be present
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What is an Indicator Microorganism?
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A NATURALLY occurring microorganism in food/food processing environment whose presence in indicative of the the occurrence of other organisms or conditions
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What criteria should be met in order to use an indicator organism?
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-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 |
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What is the difference between an indicator and a "surrogate" microorganism?
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Surrogate = artificially added
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What are categories of indicators?
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Indicator Microorganisms
--> can be Safety or Quality Indicator Metabolites |
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Name some common Quality Indicator Microorganisms
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TPC
Yeasts & Molds Psychrotrophic bacteria and Thermophillic bacteria Thermoduric bacteria --> this is v. broad |
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What are Safety Indicator Microorganism used to indicate?
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Human contamination
Fecal contamination Pathogen survival and growth |
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Name three types of Indicator Metabolites
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1. Protein and amino acid degradation compounds (cadaverine, putrescine)
2. Organic acids (lactic, propionic, butyric) 3. Volatile compounds (diacetyl in dairy) |
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Fecal Indicators should also posses what qualities?
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-Ideally should only occur in intestine
-should occur in high # in feces -should posses heat resistance to environment -detectable at low levels |
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What are some common fecal indicators?
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E.coli (best)
Enterococci Coliphages Fecal coliforms (but not so much) |
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What are some common pathogen indicators?
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E.coli for E.coli O157:H7
Listeria spp. for Listeria monocytogenes |
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Define Pathogen
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A microorganism that causes disease and makes people sick
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Define Infection
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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)
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What is an outbreak?
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Typically 2 or more cases but botulism is the exception - only one case
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What is definition of Infection Dose?
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The number of cells or virus particles needed to develop symptions
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Define incubation time?
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The time between the ingestion of food and the time until symptoms develop
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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 |
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What is toxico-infection?
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Pathogenic cells that release toxin once they're inside the body; again, the toxin is responsible for the sickness.
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What classes of symptoms can develop when infected with a pathogen?
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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) |
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Which are the gram positive pathogens?
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vacs By CLaSSes
Bacillus - sporulating rod Clostridium -sporulating rod Listeria - rods Streptococcus -endospore forming cocci Staphylococcus -ditto |
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Top 5 baterial causes of illness?
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1. Campylobacter (jejuni/coli)
2. Salmonella 3. Clostridium Perfringes 4. Staphylococcus (intoxication) 5. E.coli (toxigenic and other) |
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Top bacterial causes of death?
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Salmonella, Listeria by far (they're also the costliest) Also causes the most outbreaks along with E.coli
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What is Toxoplasma gondii?
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Particulary lethal parasite that especially affects pregnant women. 375 deaths in 1999.
NOTE: NOT THE MOST COMMON though - most common is giardia lamblia |
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Most common pathogenic virus?
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Norwalk-like virus (also tops in # of deaths)
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What does "obligate" mean?
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Introduced by human
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What is passive vs. active surveilence?
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Determines if stool sample test need to be run to check for pathogen.
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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 |
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What family is Salmonella part of?
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Enterobacteriaceae
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What was the disease salmonella used to cause? Now?
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Typhoid fever; now it's non-typhoid salmonellosis (clever). Cases are rising.
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What is the bacteria most commonly implicated in outbreaks?
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Salmonell. it accounted for almost 60% of all outbreaks in 2004
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What testing is required for salmonella?
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Salmonella has a zero-tolerance
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What are the most common serovars of Salmonella?
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Typhimurium, Enteritidis, Newport and Heildelberg. There are 2463 total serovars.
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Other characteristics of Salmonella?
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Doesn't ferment lactose, produces H2S, >0.94 awm grows at ph=4; Stress resistant: acid, salt, freezing
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What was Leeuwenhook's big contribution to microb?
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First to see "little animals" through ingenious device (microscope)
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What was Appert's big contribution to microb?
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Invented what evolved into the modern-day canning process
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What was Koch's big contribution to microb?
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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 |
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Where was HAACP developed?
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Pillsbury
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What are the three groups in the "three domain system" of living organisms?
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Archaea, Bacteria (both are prokaryotes) and Eukarya
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In the "three domain system" which groups contain food borne pathogens?
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Bacteria (duh) and Eukarya (molds, yeasts)
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How are serovars differentiated?
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By the specific antigens that they react with
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Name the 6 groups of food microorganisms.
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1. Bacteria
2. Yeasts 3. Molds 4. Protozoa 5. Viruses 6. Protozoa |
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"Eschericia" is what level of taxonimy classification?
Coli? Enterobacteriacea? |
Escherichia: GENERA
Coli: Species Entero.: Family |
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Of the 6 groups of food microorganisms, which is the smallest in size?
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Bacteria: on the order of 1 micron
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How do bacteria reproduce?
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Growth by division
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What is the compound found in bacterial cell walls?
What are bacterial membranes made of? |
Peptidoglycan
Phospholipid bi-layers |
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What does halotolerant mean?
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Capable of surviving high salt concentrations
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What is an osmophilic bacteria?
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One that is tolerant of high osmotic pressue
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Yeast:
Cell size? Shape? Reproduction? |
2-30 microns (larger than bacteria)
- Unicellular: oval, spherical or elongated -division or budding |
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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! |
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Cell size of mold?
General structure? |
Bigger than bacteria.
20-100 micron. General structure - filamentous: form hyphae; multicellula |
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What are "obligate parasites"? Name an example
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They cannot live independent of a host - Viruses are an example of an obligate parasite
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What is a bacteriophage?
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A virus that attacks a bacteria
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Name three common food spoilage microbes
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Pseudomonas
Lactobacillus Bacillus |
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Name three common molds in food
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Aspergillus
Fusarium Penicillum |
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Name the pathogenic bacteria; which ones are gram positive?
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vacs By CLaSSes
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One source of microbes in food is epiphytic flora; what is this?
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Epiphytic flora are plants that grow attached to host (another plant)
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What does CFU stand for?
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Colony Forming Units
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What is the generation time of a microorganism?
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The time it takes to divide in two (or, in other words, to double). "G"; it's related to the specific growth rate, u.
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What are the phases in a microbial growth curve?
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Lag, exponential (growth), stationary, death
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What is the specific growth rate of a microorganism?
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It's defined as
'u' in: N = No* e^(u*t) |
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In a plot of Ln (N) vs. time (where N = # of microbes), what is the slope?
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u the specific growth rate
ln (n/no) = u(t-to) |
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What is the fastest generation time , g, ever recorded?
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8 minutes for clostridium perfringes.
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Define:
-Symbiotic growth -Synergistic growth -antagonistic growth |
-need each other
-complement each other -kill each other |
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What is diauxic growth?
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Change in growth rate due to change in substrate - cell is busy producing enzymes needed to metabolize new energy source. Cause of "lag" phase.
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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 |
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Why does low pH inhibit or kill microbes?
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Homeostasis must be maintained. The cell expends significant energy to expel H+ ions; the more energy it expends, the less it has for growth.
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Why are acids different in their ability to inhibit or kill microbes?
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It's related to the hydrophobicity of the organic acid: the more hydrophobic, the easier they can cross the cell's membranes.
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Define water activity
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aw = %RH
it's the "available" water for microorganisms to grow or rxs to take place |
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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 |
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What is the oxidation/reduction potential of a food?
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It's how oxidized or reduced a food is. If it's more oxidized, there is more O2 around and aerobes will survive.
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What condition influence the food Oxidation/Reduction potential?
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- packaging: vacuum, gas flush, antioxidants
and!! presence of -SH reducing groups. (-SH in meat - reacts w/O2 - anaerobes can live) |
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Why can't anaerobes survive in oxygenated environment?
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They don't have the mechanism to dispose of aerobic metabolic waste
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What are some natural antimicrobials?
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Lysozyme (eggs)
Lactoferrin (Milk) |
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What are bacteriocins?
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Toxins produced by bacteria to kill off other bacteria: a method of competitive exclusion
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How does the temperature affect the growth rate of a bactera?
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Arrhenius:
Rate=Rateo*e^(-Ea/RT) But only in range where microbe CAN grow. |
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What gases have an antimicrobial property?
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CO2 and ozone
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What is the taxonomy family that encompasses spore-forming bacteria?
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Bacillaceae
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What are the two most common spore-forming bacteria?
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Bacillus and Clostridium
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What is an endospore?
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A spore formed by a bacteria
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What are three very important layers of a spore?
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Coats, cortex, core
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What is the secret to the durability of a spore?
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The cortex - it's the thickest layer of a spore and surrounds the core which contains all the good bits (dna, ribosomes)
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What is a spore's cortex comprised of?
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Besides peptidoglycan, it contains dipicolinic acid (DPA)which is responsible for much of the spore's resistance
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What are some of the reasons spores are able to survive harsh conditions?
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Thick cortex layer with DPA/peptidoglycan
-very low moisture content |
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In what type of foods is inactivation of spores a primary concern?
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Low-acid canned foods
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What is Pflug famous for?
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His work modeling microbial death curve and modeling of spore inactivation.
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Are spores metabolically active?
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No; they are dormant
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Draw the sporeformer cycle; At what stage can toxins be produced?
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Toxins can be produced during the sporulation phase;
Vegetative cells->(sporulation) dormant spore->(activation) activated sport->(initiation)germinated spore->(outgrowth) Veg. cell |
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How do we control spores in food?
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Eliminate or removal, inhibition: prevents activation or dormant spores!
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What is an endospore?
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A spore formed by a bacteria
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What is the 'D' value of a spore?
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The time required to achieve 90% reduction at T=121C
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What are three very important layers of a spore?
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Coats, cortex, core
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What bacteria have zero tolerance laws?
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Listeria monocytogenes
E.coli O157:H7 Enterobacter sakazakii --> 0/25g |
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What is the secret to the durability of a spore?
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The cortex - it's the thickest layer of a spore and surrounds the core which contains all the good bits (dna, ribosomes)
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Why is zero tolerance 0/25g and not just 0?
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Limitation in detection
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Name some challenges in the microbiological analysis of food
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-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 |
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What is a spore's cortex comprised of?
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Besides peptidoglycan, it contains dipicolinic acid (DPA)which is responsible for much of the spore's resistance
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What microbiological method types can be used for quantitative purposed?
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TPC; microscopic methods; and others including physical, biochemical and molecular
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What are some of the reasons spores are able to survive harsh conditions?
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Thick cortex layer with DPA/peptidoglycan
-very low moisture content |
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In what type of foods is inactivation of spores a primary concern?
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Low-acid canned foods
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What is Pflug famous for?
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His work modeling microbial death curve and modeling of spore inactivation.
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Are spores metabolically active?
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No; they are dormant
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Draw the sporeformer cycle; At what stage can toxins be produced?
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Toxins can be produced during the sporulation phase;
Vegetative cells->(sporulation) dormant spore->(activation) activated sport->(initiation)germinated spore->(outgrowth) Veg. cell |
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How do we control spores in food?
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Eliminate or removal, inhibition: prevents activation or dormant spores!
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What is the 'D' value of a spore?
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The time required to achieve 90% reduction at T=121C
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What bacteria have zero tolerance laws?
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Listeria monocytogenes
E.coli O157:H7 Enterobacter sakazakii --> 0/25g |
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Why is zero tolerance 0/25g and not just 0?
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Limitation in detection
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Name some challenges in the microbiological analysis of food
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-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 |
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What microbiological method types can be used for quantitative purposed?
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TPC; microscopic methods; and others including physical, biochemical and molecular
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Salmonella Characteristics?
(gram stain/shape/temperature/spores) |
gram negative
facultative anaerobe rod shaped w/flagella (motile) mesophilic but some serovars 5, 50ºC nonsporulating |
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What family does salmonella belong to?
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Enterobacteriaceae
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How many sub species of Salmonella are there? How many serovrs?
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6 subspecies; ~2500 serovars - most are in subspecies enterica
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Name the most common serovars of Salmonella in order and the foods they are found in
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Typhemurium - ALL
Enteritidis - Eggs Newport - ALL Heidelberg - ALL |
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Name some differentiating characteristic of Salmonella
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- Does not ferment lactose
- Catalase positive - Produces H2S - Requires aw.94 and up - pH 4.0 min growth - Stress resistant: acid, salt, freezing |
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Typhoid fever is caused by what serovar?
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S. Typhi & S. Paratyphi
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Which serovars are responsible for non-typhoid salmonellosis?
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All by S. Typhi & S. Paratyphi!! 2400+ serovars cause it! Almost all strains of salmonella are pathogenic
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What is the GI disease caused by Salmonellosis called?
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Enterocolitis - cramps, diarrhea, nausea, vomiting
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Incubation period of Salmonellosis? Infectious dose?
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8 -72 hrs (vs. 7 to 28 days w/typhoid fever!)
Dose: 10-10^6 |
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How long does it take for remission of symptoms w/salmonellosis? Is the person "clean" then?
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~5 days, but asymptomatic excretion for weeks: they can infect others!
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Describe the pathogenesis of Salmonella.
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It infects (i.e. the organism is what makes people sick) by invading cells:
1. Attachment 2. Invade 3. Growth, survival |
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What cells does Salmonella infect?
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It invades enterocytes and M cells
"Intracellular" pathogen |
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List some virulence factors of Salmonella
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- appendage proteins
- chaperone proteins - Type III secretion systems - Outer membrane secretion channels - Enterotoxin (acid tolerance response) - Sideophores |
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What does commensal mean?
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Commensal refers to organisms that live off a host environment but with no ill harm
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Top 3 food implicated with Salmonella outbreak?
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1. multiple vehicle (could not determine which ingredient)
2. eggs 3. beef |
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Which foods contain Salmonella most often?
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1. Poultry
2. Turkey 3. Beef 4. Pork --> extremely prevalent in herds - 50-90% |
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How is salmonella detected?
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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 |
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Principles of Salmonella methods are based on what?
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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) |
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Is salmonella "emerging"?
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No, but some strains are becoming antibiotic resistant
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Which serovar(s) of salmonella is antibiotic resistant?
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Heidelberg; Newport
Typhimurium DT104 - resistant to 5 antibiotics; epidemic in UK |
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Biggest Outbreak of Salmonella? Strain?
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Eggs - Schwann's. Enteritidis.
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