Food Science #2 - Final: Part Two Flashcards
1
Q
Why is Detection of Foodborne Pathogens needed?
A
- Epidemiology studies = surveillance, outbreaks, investigation;
- Clinical use = determine treatment;
- Food companies = production control, identify sanitation procedures, and prevent recalls;
- Regulatory research;
- Research
2
Q
What are the criteria for a good method of detection?
A
- Speed;
- Sensitivity (false-negatives);
- Specific (false-positives);
- Multiple agents;
- Throughout (ease of use);
- Application in food samples;
- Cost
3
Q
What are the types of Detection Methods?
A
- Culture;
- Immunological method;
- Molecular
4
Q
What are the differences in “culture”?
A
“A” culture is the microorganisms that grow in a culture medium;
“To” culture means to grow the microorganisms in a culture medium
5
Q
What is Culture Media?
A
- Solutions containing all of the nutrients and necessary physical growth parameters necessary for microbial growth;
- EX: Vibrio needs a salt component
6
Q
What must be remembered when trying to culture bacteria?
A
Not ALL microorganisms can be grown in ANY given culture medium, and some can’t grow in any known medium
7
Q
How can culture media be distinguished QUALITATIVELY?
A
- Solid vs. Broth;
- Non-Synthetic vs. Chemically Defined;
- Reducing - O2 Scavenging;
- Selective (suppresses);
- Differential (distinguishes)
8
Q
What is Solid Medium (AGAR)?
A
- Contain a solidifying agent, AGAR;
- Has physical structure (broth has none) — colonies can grow;
- Types =
1. Slants;
2. Stabs;
3. Petri Dishes
9
Q
What is a Colony?
A
A pile or mass of a sufficiently large enough number of cells growing on or in solid medium, that they are visible to the naked eye
10
Q
What is Broth Medium?
A
LACKING solidifying agent, such as Agar
11
Q
What is Chemically Undefined or Non-Synthetic Medium?
A
-Contain at least ONE component that is neither purified nor completely characterized nor even completely consistent from batch to batch;
-Usually have partially DIGESTED PROTEIN from various organisms;
-Solid or broth
EX: Broth from yeast (used for Vit. B)
12
Q
What is SIMPLE Non-Synthetic Medium?
A
A SIMPLE non-synthetic medium, operationally defined, is capable of meeting the nutrient requirements of organisms requiring FEW growth factors
13
Q
What is COMPLEX Non-Synthetic Medium?
A
- COMPLEX supplies additional (more) growth factors;
- COMPLEX are able to support more fastidious microorganisms than SIMPLE
14
Q
What is Chemically DEFINED Medium?
A
- One prepared from PURIFIED ingredients and therefore whose EXACT composition is known;
- Must know EXACTLY what the microorganism’s GROWTH REQUIREMENTS are (trial and error)
15
Q
What are Pre-Prepared Medium?
A
-Premixed in an often dehydrated and powdered state
16
Q
What is Ready-to-Use Media?
A
- Sterilized and ready to use;
- Particularly useful when lacking an AUTOCLAVE, filtration devices, or desire to use pre-prepared media
17
Q
What is Enriched Medium?
A
- Pre-prared medium to which MORE growth factors have been added;
- May be added individually ore in complex mixtures;
- May be chemically DEFINED, chemically Undefined complex/simple;
- EX: Blood Agar (complex medium with whole blood added)
18
Q
What is Reducing Medium?
A
- Oxygen scavenging;
- Used for growing OBLIGATE ANAEROBES (ex. clostridium);
- Contain chemicals (reducing agents) that DEPLETE molecular O2
19
Q
What is Selective Medium?
A
- Differential growth suppression =
- Supresses the growth of some microorganisms and allowing other;
- SOLID medium is employed with SELECTIVE medium so individual colonies are isolated
20
Q
Examples of SELECTIVE Medium
A
- Mannitol Salt Agar = against non-skin flora (used for staph);
- Maccokey Agar = against gram-positive;
- Eosin Methylene Blue = against gram-positive
21
Q
What is Differential Medium?
A
- Allows the growth of more than one microorganisms, but with MORPHOLOGICAL DIFFERENCES;
- Almost any medium containing specific substrate and well tailored indicators is differential
22
Q
Examples of DIFFERENTIAL Medium
A
- Mannitol Salt Agar (fermentation = YELLOW);
- Blood Agar (hemolysis);
- Macconkey Agar (Lactose = YELLOW);
- Eoisin-Methylene Blue Agar (Green metallic sheen; E. coli)
23
Q
What in an Enrichment Culture?
A
- Used to increase the relative concentration of certain microorganisms in the culture prior to plating on solid, selective medium;
- BROTH medium
24
Q
What is the PURE Culture Technique?
A
- Method of culturing in which all of the individuals in a culture have descended from a SINGLE individual = CLONING;
- Used to =
1. Inhibit evolutionary change in cultures;
2. Allow characterization of microorganisms WITHOUT CONFOUNDING microorganisms
25
What is the basis of a Pure Culture?
- to ISOLATE, in colonies, individual cells and their descendants from other colonies of individual cells;
- Usually done on Petri Dishes = Streaking, Spreading, Pouring
26
When should isolation be repeated?
When isolating from complex mixtures need to re-streak at least once;
- Makes sure than colony is from only a single individual cell;
- After isolation from wild, characterize by inoculation on DIFFERENTIAL media to help identify
27
What is a Pour Plate?
- A method of melted agar inoculated followed by Petri Dish incubation;
- Used for QUANTIFYING microorganisms in Solid Medium;
- Embedded colonies supply sufficient oxygen deficient environment that can allow growth of microaerophiles
28
What are the step of making a Pour Plate?
1. Cultures are inoculated into melted agar cooled to 45C;
2. Liquid is mixed well then poured on petri dish;
3. Colonies form WITHIN agar matrix rather than ON top as with streaking/spreading
29
What is a Spreading Plate?
- Another method of QUANTIFYING microbes on SOLID medium;
- Instead of embedding into agar (pour method), liquid cultures are SPREAD on the agar surface with a hockey stick;
- Advantage = Cultures are never exposed to 45C melted agar temps
30
What is Preserving Cultures Important?
1. Scientific reasons;
2. Indentification;
3. Vaccine production;
4. Industrial use
31
What are the methods of Preserving Cultures?
1. Refrigeration;
2. Stabs;
3. Slants;
4. Lyophilization (Freeze dry);
5. Freezing
32
When is Refrigeration used to preserve cultures?
(4C);
- SHORT periods of times;
- Broth culures — don’t last long;
- Stabs;
- Slants;
- Streak
33
What is Stabbing?
- Cultures are stabbed deeply into agar using an inoculation needle;
- Stabs are incubated until VISIBLE cultures from, then sealed at stored at RT or lower
34
What is the Slant Method?
- Cultures may be streaked onto the surface of SOLID medium in a SLANT;
- Slants incubated until visible culture formation then sealed and stored at RT or lower
35
What is Lyphophilization or Freeze Drying?
- Lypophilization is freeze drying of cultures;
- Frozen and dried under vacuum;
- to REVIVE cultures, REHYDRATED by BROTH;
- LONG TERM storage
36
How are cultures Frozen with Protection?
1. BROTH cultures are pelleted mixed with other ingredients to limit freezer damage and then frozen to −50C to −95C (mostly −80C);
2. Thawed and transferred to Broth to REVIVE;
3. Effective LONG term method
37
What is Colony Morphology?
- Gives important clues to IDENTIFY microorganisms;
1. One SIZE of colony;
2. Type of MARGIN;
3. Colony ELEVATION;
4. Colony TEXTURE:
5. LIGHT and transmission;
6. Colony PIGMENTATION
38
What determines Colony SIZE?
- Dependent not just on the TYPE of organisms but also the growth MEDIUM and NUMBER of colonies and culture MEDIA characteristics;
- Colonies SMALLER when greater than a certain amount are present
39
How long does it take colony SIZE to stabilize?
```
-After a day or two of incubation;
Exceptions =
1. Slow growers;
2. Conditions that promote slow growth;
— Growth will continue past first few days, especially when steps are taken to ensure slow growth
```
40
What are the variations in colony MARGIN?
1. Entire;
2. Undulating;
3. Erose;
4. Iobate;
5. Filamentous
41
How does colony ELEVATION vary?
-Elevations vary between both microorganisms and growth conditions and within individual colonies
42
What are the different colony ELEVATIONS?
1. Flat;
2. Raised;
3. Convex;
4. Pulvinate;
5. Umbonate
43
What are the possible colony TEXTURES?
1. Shiny to dull;
2. Smooth to wrinkled;
3. Rough;
4. Granular;
5. Mucoid (capsule)
* *A Shiny, smooth and/or mucoid appearance tends to be associated with the presence of CAPSULAR material
44
How can colony LIGHT transmission vary?
1. Complete transparent;
2. Through intermediate (translucent) — some light;
3. Through completely lack (opaque) — NO light
45
What is colony PIGMENTATION?
- Colonies can be a rainbow of colors;
| - Many times depending upon the media they are on
46
(EXAM) What was the most E. Coli infected area of the take-home swab?
SINK
47
(EXAM) What is the order of incidence of Marine Toxins in the US?
1. Scrombrotoxic Fish;
2. Ciguatera;
3. Paralytic Shellfish Poison;
4. Neurotoxic Shellfish Poison;
5. Amnesic Shellfish Poison
48
What is the Conventional Culture Method?
- Enrichment/Isolation procedure;
| - “Gold Standard"
49
What are the steps of Enrichment/Isolation Procedure?
1. Take Food Sample;
2. Enrich sample in broth;
3. Plate on selective agar or differential agar;
4. Plate on non-selective agar;
5. Store for subsequent confirmation
50
What are the Rapid Methods Used for HACCP?
1. Support sanitation;
2. Measure process control;
3. Identification of pathogens
51
What are the rapid methods for Sanitation Testing?
* Environment microbiological monitoring =
1. Efficiency of sanitation;
2. Frequency required for sanitation;
3. Environmental sources of microorganisms;
4. Frequency required for special maintenance procedures (air filters);
5. Sanitary design for equipment
52
What are Rapid Methods for Sanitation Testing?
1. Contact plate;
2. Contact plate (microbial analysis);
3. Sponge (microbial analysis);
4. Swabbing (microbial analysis);
5. Protein and CHO analysis;
6. ATP Bioluminescence Technology;
7. ATP Bioluminescence Technology;
8. Luminator -T
53
What is a Contact Plate?
- Pressing a solidified nutrient agar against environmental surface for 5 seconds;
- Plates incubated and direct microbial determined;
- Rodac contact plate;
- Hycon contact slide
54
What is the microbial analysis method of a Contact Plate?
* 3M Petrifilm Plates;
- Open film;
- 1ml sterile DH2O on surface;
- Close film and allow agar medium to rehydrate;
- Apply to equipment surface;
- Close film and incubate
55
What is the Sponge method of microbial analysis of Sanitation Testing?
1. Rehydrate sponge in neutralization broth;
2. Collect samples and place in sterile bag;
3. Add enrichment broth;
4. Incubate bag;
5. Plate the growth
56
What is the Swabbing method of microbial analysis for Sanitation Testing?
1. West swab with broth in tube;
2. Rub swab over the desired surface;
3. Return swab to tube;
4. Release bacteria from swab;
5. Pour 1ml onto plate;
6. Incubate;
7. Calculate bacteria
57
What are the steps to Protein or Carb Analysis?
1. Sample a surface and expose to chemicals;
2. Color change indicates presence of proteins and/or carbs;
3. NOT appropriate for surfaces soiled by fat;
—VERIcleen;
—FLASH
58
What is ATP Bioluminescence Technology?
- Indicate if sanitation of processing equipment is acceptable;
- Determine if incoming products conform to acceptable standards;
- Several companies manufacture portable hand-held instruments
59
What are the steps of ATP Bioluminescence Technology?
1. Surface of equipment is swabbed;
2. Swab placed into a reagent that extracts ATP from microorganism;
3. ATP reacted with Luciferin-luciferase;
4. Measure of light emitted that is proportional to the amount of ATP and therefore biomass
60
What is Luminator-T?
- Download to Charmlink or any standard spreadsheet program;
- Allows trending and analysis of individual measurements parameters;
- Identify potential cause/effects relationships
61
What are the Rapid Methods for Measuring Process Control?
- Monitor quality of INCOMING product - meet standards;
- Verify processing - controls spoilage and pathogens;
- Monitor FINISHED product = determines SHELF LIFE;
- 3M Petrifilm;
- SimPlate
62
(EXAM) What is 3M Petrifilm. E. Coli/Coliform Count Plate?
1. Contains modified VIOLET RED BILE (VRB) nutrients;
2. E. Coli and total coliform count results in ONE test;
3. RED colonies with gas = COLIFORMS:
4. BLUE colonies with gas = E. Coli;
5. Incubation 24-48 hours;
* *AOAC Official Method
63
What is the SimPlate Method of Rapid Methods of Processing Control?
1. Food sample added to CEc media (coliform and E. Coli);
2. Media added to plates;
3. Excess media poured out of the plate;
4. Plates incubated for 24 hours;
5. Results =
—Coliforms = ORANGE to RED;
— E. Coli = wells that fluorescence when exposed to UV light
64
What are the Rapid Methods for Identification of Foodborne Pathogens?
1. Antibody-based methods;
2. Dehydrated media minikit — specific level in 24 hrs;
3. DNA based methods (PCR, DNA probe)
65
What are the Antibody-Based Methods?
*Several methods available;
1. Antibodies specific to surface proteins, flagellum or toxins;
2. Identifies to specific level
—POLYCLONAL antibodies recognize MULTIPLE proteins;
—MONOCLONAL antibodies recognize SINGLE proteins
66
What is Assurance EIA?
* Enzyme-linked immunoassay;
- 96-well micro titer plate with break apart wells;
- Tests available for Listeria, Campylobacter and Salmonella;
* AOAC Official Method
67
What is Immunofluorescence?
- Antibodies couple to fluorescent dyes;
- POSITIVE cells will fluoresce under a fluorescence microscope;
- Mini VIDAS;
* *AOAC Official Method
68
What is Latex Agglutination?
- Antibodies are couple to latex microspheres;
- Visible clumping or agglutination confirms to positive reaction;
- Tests for Salmonella, Shigella, Campylobacter, and E. Coli
69
What is Immunoprecipitate Detection?
- Uses a chromatographic matrix with antibodies that precipitates such as colored latex particles or colloidal gold;
- Developed for several foodborne pathogens;
- Extremely rapid — 10 mins;
- VIP AOAC Official Method;
- Singlepath
70
What is Immunoblot?
--Direct plating using antibodies for identification;
-Overlay colonies with membranes and treat with antibodies;
-Can determine the amount of bacteria in a food sample;
— Results in 3 hours;
—Methods can develop for most bacteria
71
What are Dehydrated Minikits?
- Contained dehydrated media;
- Media hydrated when pure bacterial culture is added;
- Each test strip contains well with differential media for a specific organism;
- Advantages, longer shelf-life, minimal contamination. light weight
72
What are the Biochemical set Strips by API Systems?
- Pure culture is inoculated into well with dehydrated media;
- Test strips incubated 24 hours;
- Color reaction recorded in a 7-digit code;
- Panel read and interpreted by computer
* *AOAC Official Method
73
What are the DNA Based Methods of testing?
1. DNA Probe Hybridization;
| 2. Polymerase Chain Reaction (PCR)
74
DNA Probe Hybridization
- Direct plating using DNA probes for identification;
- Can determine the amount of bacteria in a food sample;
- Results within 8 hours;
- V. vulnificus and V. parahaemolyticus mathod available on BAM website
75
Polymerase Chain Reaction
- Extremely rapid;
- Amplify specific sequences of DNA;
- Need an enrichment step (PCR can detect DEAD microorganisms)
76
What are the PCR based methods?
BAX AOAC Official Method;
- 96 different samples analyzed every 4 hours;
- Results as positive or negative (Can’t innumerate);
- Very accurate, high sensitivity and specificity
77
What is the Smart Cycler method for measuring process control?
- Up to 96 independently programmable reaction sites;
- Results in 30 minutes;
- MULTIPLE Assays = more than one pathogen in one reaction;
- Can determine concentration of UNKNOWN samples
78
What are the Performance Standards for Identification Methods of Foodborne Pathogen methods?
* USDA/FSIS Requirements =
1. Senitivity > 97%;
2. Sepcificity >96%;
3. False negative < 3%;
4. False positive <4%
- AOCA approved methods
79
(EXAM) What is a Foodborne Outbreak?
The occurrence of two or more cases of similar illness resulting from ingestion of a common food;
-EXCEPT with clostridium botulinum ONE CASE = outbreak = CDC investigation, more than 50% of infection people will die!
80
(EXAM) What is the Purpose of Foodborne Outbreak Investigations?
1. Identify illnesses and the CAUSATIVE AGENT is FOOD BORNE;
2. Detect the CAUSATIVE AGENT and implicated FOOD:
3. Determine SOURCE and mode of TRANSMISSION;
4. STOP the outbreak and PREVENT further exposure;
5. Gather inform to PREVENT FUTURE outbreaks
81
What should be done BEFORE an outbreak occurs (which should prevent)?
* *Develop a food borne disease surveillance system =
1. Organize system and develop procedures;
2. Assign responsibility;
3. Establish an investigation team;
4. Train staff;
5. Assemble materials
82
What is included in the PART ONE of Investigating an OUTBREAK?
1. Receiving NOTIFICATION;
2. Interviewing (all complaints);
3. Verify DIAGNOSIS;
4. DEVELOP A CASE DEFINITION;
5. Make epidemiological association;
6. Form HYPOTHESIS:
7. Expand the investigation = Part 2
83
What is a CASE? (EXAM)
A person having signs and symptoms characteristic of a likely syndrome within a period of time or a person from whom a specific pathogen was isolated
84
What is a CONFIRMED Case?
*ISOLATION and LAB Work -
A person has S/S that are clinically compatible with the disease under consideration, and for which there is either an ISOLATION of the etiologic agent or a four-fold or greater rise in ANTIBODY titer
85
What is a PRESUMPTIVE Case?
* NO Isolation/Samples;
- A person has S/S that are clinically compatible with the disease under consideration and there is a lab evidence of a infection (less than 4x rise in antibody titer) but there is NO ISOLATION of the etiologic agent or NO SAMPLES were collected
86
What is a SUSPECTED Case?
A person has S/S that are clinically compatible with the disease under consideration BUT LAB evidence is ABSENT, INCONCLUSIVE OR INCOMPLETE
87
What is a CONTROL?
A person who is NOT ill but has other characteristics of the cases;
-A control may be a well family member or a neighbor that remained well but had the SAME exposure
88
What is included in PART TWO of Investigating an outbreak?
1. Plan ON-SITE investigation;
2. Meet managers;
3. Draw a FLOW DIAGRAM of operations;
4. Review MONITORING Recods;
5. INTERVIEW food workers;
6. Conduct HAZARD ANALYSIS:
7. Identify CONTRIBUTING FACTORS to outbreak;
8. Collect SAMPLES of suspect foods;
9. Determine the SOURCE of contamination
89
(EXAM) What QUESTIONS must be answered in a CASE Definition?
- WHAT were the symptoms?;
- WHEN did the infection occur?;
- WHERE did the infection occur?;
- WHO may have been affected?
90
What is a Common-Source of Point-Source Outbreak?
* Most food borne!;
- Individuals are exposed to the infection at the SAME time;
- Epidemic curve has a SHARP RISE and slowly tapers off
91
What is a Propagated-Source or Person-to-Person Outbreak?
- Spread person-to-person through fecal-oral route;
| - Epidemic curve has progressive peaks, about one incubation period apart
92
What is a Continual-Source outbreak?
-Source remains contaminated and person continue to be exposed;
EX: Contaminated water supply;
-Epidemic curve has a gradual rise and then plateaus
93
What DATA ANALYSIS is done during the investigation of a food borne outbreak?
- Determine the predominant S/S;
- Calculate the INCUBATION PERIOD (help determine date of infection);
- Determine responsible MEAL;
- Calculate food-specific ATTACK RATES;
- Calculate ODDS RATIO;
- Test STATISTICAL significance
94
What is an Epidemic Curve?
A graph that depicts TIME DISTRIBUTION of onset of initial symptoms for all cases that are associated with the disease outbreak;
-Each case is represented as a small square;
X= date;
Y= number of outbreaks
95
What is the Food Specific Attack Rate?
Compares the illness rate among those who ingested specific foods at an even or meal tho the illness rate of those who ere are the event but DID NOT ingest those items
96
Formula for Food-Specific Attack Rate
(Number of people who GOT SICK) / (Total number of people exposed or unexposed) x 100
97
What is the Food-Specific Attack Ration/Difference?
- The ratio/difference between attack rate of those exposed and not exposed;
- The food with the biggest ratio or the greatest difference between the two rates is suspected
98
What is the Relative Risk formula?
(Attack rate of ILL who ATE food) / (Attack rate of who did NOT eat food)
