NUFS 363 MT2
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NUFS 363 MT2
NUFS 363 MT2
NU FS 363 MT1-MT2
What host defense mechanisms are there in the stomach?
Control of rate of flow
What host defense mechanisms are there in the intestine?
Genetic resistance to invasion
What are the three most frequent causes of foodborne illness in Canada
What is Gastroenteritis, and what are some symptoms.
Inflammation of mucosa or submucosa of stomach and intestines
Nausea, vomiting, diarrhea, pain
What is diarrhea
Frequent and/or watery stools, loss of electrolytes and fluids
What is dysentry, and what are some symptoms?
Inflammation of mucosa of large intestine, blood and pus in stools
Pain, cramps, high fever, convulsions
What is cholera-like diarrhea?
"rice water" diarrhea due to cholera toxin (CT)
What is hemorrhagic colitis?
Bloody diarrhea, cramps, low or no fever
What is a bacterial toxin?
Pathogen classified as causing foodborne infections that produce toxins as virulence factors
What are the classifications of intoxications?
Location of production
: exo, endo
Site of action
: entero, cyto, neuro
Type of toxin
: Heat labile, heat stabile
What is serological typing?
Using surface antigens to help name bacteria
What are the three important surface antigens used for serological typing?
O-somatic - lipopolysaccharide
H- flagellar - protein
K- Capsular - polysaccharide
What are the two broad categories of intestinal infections?
What are six gut localized intestinal infections?
Enterovirulent E. coli
What are the 2 more common, and 3 infrequent systemic infections from intestinal infections?
: Typhoid Salmonella, Salmonella enterica
: Shigella, Yersinia enterocolitica, Non-typhoid salmonella
What is unique about Salmonella serovars?
Each unique serovar yield a different nomenclature for Salmonella
What are three key examples of Campylobacteriosis that cause gasteroenteritis? Where are they commonly found?
Campylobacter jejuni (Animals and birds)
Campylobacter coli (Pigs)
Heliobacter pylori (stomach ulcers)
What is campylobacteriosis most commonly caused by?
What is the temperature range of Campylobacter jejuni
What percentage of NaCl is bacteriocidal for Campylobacteriosis? What is the pH range?
Is Campylobacter jejuni invasive? How many cells are required?
Yes, 500 cells
Who is most susceptible for Campylobacter jejuni?
Children and young adults 15-29
What are the symptoms of a Campylobacter jejuni
Inflamation, ulcer formation
Bleeding in digestive tract
2-5 days incubation
headache (with or without fever) up to 2 days before
self limiting dysentery
diarrhea with blood and mucus
cramps, nausea, vomiting
Describe the different groups of Salmonella
: restricted to humans
-Salmonella enterica serovars Paratyphi and Typhi
Cause enteric fever in humans and higher primates
: Adapted to animals
-S. enterica serovars Dublins and Choleraesuis
-usually only in animals
-if infect humans, invasive and life threatening
: Animals to humans
-Rest of S. enterica
-Cause gastroenteritis, mild, self limiting
-severe in young and elderly
What are possible Salmonella causes of gastroenteritis?
All Salmonella in foods
What is the most common Salmonella? Which one is overtaking and what is it associated with?
Typhimurium is the most common
Enteritidis is overtaking (associated with eggs)
What are symptoms of group 1 salmonellosis?
Describe the growth conditions of Salmonella
5-47 degrees, optimum 35-37
pH 4.1-9, optimum 6.5-7.5
Aerobic or anaerobic
Salt < 6%
What poses an increased risk for Salmonella
use of antacids
Where has multidrug resistance been traced to?
What are resistant serovars of salmonella?
What is a difference between Salmonella serovar Typhimurium DT104 and Enteritidis pt4?
: primarily from cattle, heat resistant, high mortality rate
: Invades broiler chicks
Describe the growing conditions of Yersinia entercolotica
Grow 0-44 degrees
What is Yersinia enterocolitica destroyed by?
Describe the disease caused by Yersinia entercolitica and associated symptoms
: enters SI and taken up by cells
-if macrophages: lymph nodes and spleen
Symptoms: Abdominal pain, diarrhea, vomiting, fever, septicemia, meningitis, urinary tract infections, rheumatoid arthritis
What is another name for enterohemorrhagic e. coli?
hamburger disease (0157:H7)
shiga toxin-producing e.coli (STEC)
verocytotoxin-producing e.coli (VTEC)
Describe the toxins of enterhemorrhagic e.coli
Shiga-like toxins (cytotoxic meaning destroys protein synthesis)
Two virulence groups (SLT1 and SLT2)
: VT1 toxin - 1 aa different from shiga toxin
: VT2 toxin: less related
What is the gene responsible for dysentery with EHEC?
Adherence gene eae gene
What are symptoms of Enterhemorrhagic E. coli?
Hemorrhagic colitis (HC)
: inflamed colon, cramps, nausea, vomiting, dysentry
Hemolytic Uremic Syndrome (HUS)
: acute kidney failure
Thrombotic thrombocytopenic purpura (TTP)
: acute kidney failure, multi-organ purpura (bleeding), dementia, bruising, bowel necrosis, perforation
What is one of the most important key indicators of Enterohemorrhagic E. coli? A second, less important one?
Dysentry with no fever
: antibiotics = increased toxin release
What is another name for Enterotoxigenic E. coli?
What are two toxins produced by Enterotoxigenic E. coli (ETEC)
LT (heat labile)
-inactivated 60 degrees
-similar to cholera toxin
ST (Heat stable)
-Survives 100 degrees
What is found on the large plasmid of Enterotoxigenic E. coli?
Adherence genes (ADH)
What is the cause of epidemic cholera?
Vibrionaceae or Vibrio cholera serogroup 01
What are the symptoms of Vibrionaceae?
Rice water diarrhea
sudden onset of vomiting (without nausea)
Describe Halophilic vibrios
Caused by Vibrio parahaemolyticus
requires 1% salt
What are symptoms of Vibrio paraheamolyticus?
Mild, self limiting gastroenteritis
-Vomiting, headache, low fever, chills
What is the main cause of stomach ulcers?
What are the routes of transmission of Helicobacter pylori? (3)
1. Fecal contamination
2. Stomach to mouth
3. Endoscope cleaning
What is Listeria monocytogenes commonly described as?
Describe the infection of Listeria monocytogenes
Start with colonization of gut (invades blood)
Use of listeriolysin 0, escapes phagocytes
Use of Actin tails or extracellular protein = lysis
Which bacteria can cause a transplacental infection (still born baby)
What is a very close relative to E. coli
What are the four groups of Shigella?
S. dysenteriae (bloody stools, mucus, low volume (shallow ulcers), hemolytic uremic syndrome))
What is hemolytic uremic syndrome? What is it caused by?
Clumping of platelets within the kidneys small blood vessels resulting to reduced blood flow to the kidneys leading to kidney failure.
Can be caused by Shigella
What are symptoms of Streptococcal infections?
Sore throat, tonsillitis, fever, headache, chills, diarrhea, vomiting, muscle pain, weakness
What bacteria can cause scarlet fever and rheumatic fever and nephritis
What are the six bacteria that are bacterial infections?
Describe exo toxins
Formed outside the cell or in the medium
Describe endo toxins
Formed in outer membrane of gram negative bacteria
What are the three sites of actions of toxins?
: effect on intestine
: damages specific cell types
: affect nerves
What are key strain characteristics of Clostridium perfringens?
Five types A-E
Describe the forms of poisoning by Clostridium perfringens
-spore specific protein
superantigen (Binds brush border of epithelial cells)
Vasodilation = watery diarrhea
What are key symptoms of Clostridium perfringens?
pain, gas, diarrhea
Nausea, vomiting, fever, headache
What is a source of Campylobacter jejuni?
Raw milk, untreated water, poultry, mastisis in cows
What is a source for Salmonella?
Poultry, red meat, eggs, turtles
Alfalfa sprouts, coconuts
Chocolate bars, baby food
What is a source of Yersinia entercolitica?
What is a source of Enterohemorrhagic e. coli
linked to ruminants
cross contamination during slaughter
What are sources of enterotoxigenic e. coli?
Contaminated water, raw vegetables and fruit
What are sources of Listeria monocytogenes?
soil, dust, animal feed, sewage, animals and humans (10%)
What are sources of Shigella?
Salads, handled cooked foods, rice balls, milk, beans, strawberries, raw oysters
What are sources for streptococcal infections?
raw milk/handled foods
What are sources of Clostridium perfringens?
Ubiquitous in environment and animal intestine
Describe physical characteristics of Bacillus spp.
What are the two major types of toxins of Bacillus spp.?
Describe the emetic toxin of Bacillus spp.
Associated with cereals and starchy foods
heat stable toxin
resistant to enzymes
toxin produced in food and then ingested
Spores highly heat resistant
Describe the diarrheal toxin of bacillus spp.
Associated with meats
heat labile toxin
sensitive to enzymes
toxin produced during growth after ingestion
What are ways to control Bacillus spp. intoxications?
Proper holding and refrigeration
Prevent cross contamination
Control spore germination and growth in RTE foods
What are ways to control Clostridium perfringens?
Time and temperature (cook to above 75 degrees)
What is a source of Bacillus Spp.
Describe the physical characteristics of Staphylococcal intoxications
What are characteristics of the Staphylococcal intoxication?
Five enterotoxins (A-E) (SEA to SEE)
SEA is most toxic and common in illness
Toxins highly heat resistant (survives boiling)
DOES NOT GROW AT REFRIGERATION TEMPERATURES
What are the four types of toxins of Staphylococcal intoxication?
Alpha toxin (transmembrane pores)
pyrogenic exotoxins induce fever
Exfoliatins (intercellular splitting of epidermis)
enterotoxins (food poisoning vomiting)
Five enterotoxins as well as
What are growth characteristics of Staphylococcal intoxication?
pH=4 (4.6 if anaerobic)
: 0.83-0.86 min
7-10% salt (up to 20 limit)
What are symptoms of Staphylococcal intoxication?
Nausea, vomiting, retching, cramps, sweats, chills, low temp
What are control mechanisms of Staphylococcal intoxication?
What are sources of Staphylococcal intoxication?
What are physical characteristics of Clostridium botulinum?
: gas, spores, potent neurotoxin
What does intoxication of Clostridium botulinum block?
Blocks acetlycholine and causes flaccid paralysis
Describe the toxins of Clostridium botulinum
eight toxins A, B, C1, C2, D-G
Five main groups (1
: AB, 2: EBF, 3: CD, 4: G)
Compare type 1 and 2 Clostridium botulinum toxins
1: very potent toxin, cannot grow at refrigeration temperatures, most heat resistant spores. Signs of spoilage if organism grows
2: trouble in chilled foods (can grow at 3 degrees). No signs of obvious spoilage with growth
What are symptoms of Clostridium botulinum intoxication?
nausea, vomiting, diarrhea to constipation
vision, speech, fatigue, paralysis, death
What are sources of Clostridium botulinum?
Fish, meat, fruit and vegetables, honey
What are ways to control Clostridium botulinum?
Freezing, proper heat treatment, control growth
What are the four bacteria associated with bacterial intoxications?
Describe the flow of meat. Don't be perverted Whitney :)
Slaughter and dressing
Storage and transport
Retail or food service
Consumer purchase and handling
What are sources of animal contamination (while they are alive)
External surface (mud+feces=tag)
Not normally with circulatory system
What is TAG?
Mud + feces on hide of animal
What are the 8 bacteria most common with foodborne illenss?
Enterohemorrhagic E. coil
Other pathogenic E. coli
What are 7 prevention mechanisms of contamination done during processing of animals?
Bagging of anus
Dipping knives in hot water
Trim visible contamination
Rapid chilling of carcasses
Cleaning and sanitizing equipment
What parts of the animal are inspected post-mortem? (4)
Head for disease (tongue and several glands)
Viscera (injury, disease, parasites)
What is the goal for storage life of packaged meats?
What types of bacteria grow in refrigerated storage?
-lactic acid bacteria
When does spoilage occur with lactic acid bacteria?
When numbers reach high levels
What is the normal pH of meat? What occurs if there is no pH drop?
: dark colour and reduced storage life
Which bacteria are most commonly found if vacuum packed?
Primarily lactic acid bacteria
How is water activity of bacteria controlled? What are some organisms that will grow at low water activity (3)?
Yeast and molds
What antimicrobials are used to preserve meats
Sorbate dip (decreases mold growth)
Sodium lactate/sodium diacetate
Nitrate or nitrite (colour)
What is considered to be an acidified pH of meat? how is this achieved?
Addition of a fermentable carb
What is a bacteria that can be found in home-cured hams
What are the predominant bacteria involved with cooked and cured meats?
Lactic acid bacteria
What are acceptable bacterial counts of milk? improper hygiene? What about max levels of milk?
75 000 cfu/meal
> 1 000 000
must not exceed > 2 000 000 cfu/ml
What is masitits? the two types?
Inflammation of the mammary gland
Contagious and environmental
What are the bacteria that cause contagious mastitis? (2)
What are the bacteria that cause environmental mastitis? (6)
What is pasteurization? What bacteria remain
Destroys vegetative cells of pathogens in milk?
Some psychotropic bacteria may remain
What are the two categories of spoilage bacteria of milk?
Proteolytic (staphyloccous and pseudomonas_
What are the pathogenic bacteria in raw milk?
What are 2 potential pathogenic bacteria in pasteurized milk
What is a major mechanism of salmonellosis?
Describe the egg structure
Describe the barriers to microbial growth an egg offers
Shell and membranes
high pH 9.3
Viscosity of albumen
low non-protein nitrogen concentrations
What are the antimicrobials in eggs? their mechanisms?
Ovotransferring ( complexes fe)
Lysozyme (lyses cell wall)
Avidin (complexes biotin)
ovaflavoprotein (binds riboflavin)
Ovomucoid (enzyme inhibitor)
What are the microflora of an egg (6)
Salonella enterica (a concern)
What are environmental sources of salmonella for poultry
wildlife (free range)
What is the egg production system?
what is transovarian transmission
Ovaduct of laying hens contaminated with S. enterica ser. Enteritidis
(organism deposited on yolk before shell formation)
What organism is killed during pasteurization of eggs?
What are the hurdles present in egg-containing foods?
: 3.6 - 4
Spoilage by yeast and LAB
Compare the characteristics of fresh fruit and vegies.
: low pH
: High pH
-more concern with spoilage and safety
What are sources of microorganisms for fruits and veggies?
Contact with soil during growth
Water quality (irrigation, processing)
Manure as fertilizer
What are Saprophytic microorganisms
Get nutrients from dead or decaying material
Describe bacterial soft rot
Pectin breakdown causes mushiness and off-odours
Usually in vegetables
Pseudomonas, pectobacterium carotovora (not human or animal pathogen)
Describe mold spoilage of fruits and veggies
Can be a problem before harvest
post-harvest spoilage more important
high humidity and warm temps
toxic if produce mycotoxins
What are the reasons for an increase in produce-related foodborne illness?
Large scale production
Widespread distribution (pathogens cross borders easily)
What are three parasitic pathogens? What is the problem?
: minimal processing to reduce risk
What are the three viral pathogens associated with produce? problem?
: minimal processing to reduce risk
Why do we need to have practical methods to determine if a food is contaminated (3) ?
Determine microbial risks
Understand history of food or sample
Gather info to advice next steps in terms of storage, handling, distribution
What are the principles of total count?
Indicator of spoilage, not food safety
Changes in number in plant may indicate something has gone wrong
Monitors numbers, not diversity
What is the concept of indicator organisms?
Use the detection of one microorganism to detect others
What does an indicator organism indicate? What does it NOT do?
Presence indicates probability of a pathogen, not GUARANTEE
What is a Coliform? What is its significance?
It is a lactose fermenting enterobacteriaceae and its presence mean there was inadequate heat treatment of post pasteurization contamination
Means fecal contamination
What are the traits of a good organism? (5)
Quick, cheap and easy
Specific to contaminant
Extraenteral (survive outside habitat)
Very high concentration
Presence indicates probability, not guarantee
What do high numbers of an indicator organism increase?
Name three good indicator organisms
Enterobacteriaceae and subgroups (coliform bacteria -> E. coli)
Describe Enterobacteriaceae and its significance.
It is an indicator organism
Gram negative, non-sporulating, straight rods, acid and gas from glucose.
Detection is done on a violet red bile glucose agar (VRBG)
Coliform bacteria don't grow below 4 and are often killed by pasteurization, so presence means no pasteurization or post-pasteurization contamination
What is the significance of detection of Enterococcus Spp.
They are an indicator organism
Fecal contaminant (found in heat treated food)
Resistant to a wide variety of antibiotics
What is the significance of Clostridium perfringens detection in food?
It is an indicator organisms
Spore former (not destroyed by standard heat treatments)
Often found in food in low numbers
Not good in heat treated food because heating germinates the spores
What is the significance of Staphylococcus aureus in food?
It is an indicator organism
Good indicator in ready to eat foods and it is salt tolerant so is an indicator in high salt foods
Organism is heat sensitive
What is the significance of molds in foods?
Can be an indicator organism
Evidence of uncleanlyness
Indicator of environmental contamination
What is MPN? Describe it.
Most probable number technique
Still commonly used by industry
Lower detection limit than plating
Estimates microbial loading of food
Based on principle of dilution to extinction
Need growth conditions that show positive selective growth
How is accuracy of MPN improved?
By inoculating more than one tube of the same dilution
What are the assumptions of MPN (2)
Organisms distributed evenly in sample
Single cell can initiate recognizable growth in medium
Describe an MPN technique of 100 mL apple juice.
Inoculate 3 cultures with 10 ml, 3 with 1 mL and 3 with 0.1 mL.
Growth in all three of the 10, 1 in the 1 and none of the 0.1
Use statistics to determine the accuracy within an order of magnitude.
What is the test that is used to confirm presence of E. coli
: Gas production
: conversion of tryptophan to indole
: High acid oxidizes methyl red to a yellow
: Voges Proskauer (production of acetoin during sugar fermentation)
: Citrate utilization (colour change from green to blue and visible growth)
Under the GIMViC test, which organisms test positive for each test?
E. coli type 1, positive for GIM
E. coli type 2, positive for IM
Enterobacter aerogenes type 1, positive for ViC
Enterobacter aerogenes type 2, positive for IViC
Enterobacter cloacae positive for ViC
What is the Hydrophobic Grid Membrane Filter
Variation of MPN technique
Sample filtered through a hydrophobic grib of small cells
Filter is incubated on the desired growth medium and scored for target organisms
Works well for single cell organisms such as bacteria and yeast, but not filamentous fungi(molds)
What are the 7 rapid methods for bacterial detection?
Hydrophobic Grid Membrane Filter (HGMF)
ELISA (Enzyme-LInked ImmunoSorbent Assay)
Lateral flow immunoprecipitation
What is in a method for rapid detection? (5)
Performance (Sensitivity, specificity, accuracy, precision, reproducibility, repeatability)
Time (Total time (presumptive/confirmative), lab time)
Ease of Use (Automation, robustness, training, sample throughput, result interpretation)
Standardization (validation, accreditation)
Economics (cost/test, capital equipment, labour, running cost)
What is sensitivity? What is low sensitivity?
The proportion of test samples that truly contain the pathogen and respond positively to the test.
Low sensitivity = high rate of false negative results
What are risks of using false negatives (2)
A known positive tests negative
Underestimates food safety risk
What is specificity? What does Low specificity mean?
The proportion of samples that truly do not contain the pathogen and respond negatively to the test
Low specificity = high false positives
What are the risks of false positives (3)
A known negative sample tests positive
What are the three performance indicators?
Sensitivity, specificity, detection limit
What are the requirements for detection limits of performance indicators?
Should be low
international standard (one cell/25 g sample)
What are three methods of sampling?
Cotton Swap (CS)
-soaked in ml of neutralizing buffer
Sterile Sponge (SS)
Composite tissue (CT)
-Soaked in 10ml of neutralizing buffer
What is ELISA/
Red colour is a positive match
Describe lateral flow immunoprecipitation and what is can be used for
Sample + Demi-Fraser Broth
30 degrees for 24 hours
take 0.1 ml and put into 2mL tube and heat
Sample + Demi-Fraser Broth
30 degrees for 24 hours
take 0.1 mL and put in a tube and heat for 35 degrees for 24 hours
Denaturation, annealing, elongation (repeat lots)
Describe Real time PCR
1. In intact probes, reporter fluorescence is quenched
2. probes and the complementary DNA strand are hybridized and reporter fluorescence is still quenched
3. During PCR the probe is degraded by the Tag polymerase and the fluorescent reported is released
What are the colony number associated with E. coli detection for each of the assays?
: LOW CFU's
: 10-100 CFU/ml
: 100 CFU/ml
: 1-2 CFU/ml
: 100 CFU/ml
: 55 CFU/ml
What is the effect of stress on ELISA?
antibody reactions will decrease standard deviation and accuracy of results
What is the approximate time of each of the assays (6) ?
: up to 1 week
: 12 h to 2 d
: 2 to 24 h
: 24 h
: 6-12 h
Microarray <1 h
What is a microarray?
An assay for microorganism detection