16 - Toxico-Infections Flashcards
Key characteristics common among toxico-infections for spore formers:
1- ingestion of large numbers of live vegetative cells is usually necessary
2- vegetative cells of sporeformers do not multiply in the digestive tract, but sporulate and release toxins
Key characteristics common among toxico-infections for gram negative bacteria :
1- live cells can be ingested in moderate numbers
2- gram negative cells rapidly multiply in the digestive tract
3- many cells also die, releasing toxin
T or F: Toxins of both groups (spore formers and gram - bacteria) cause gastroenteritis symptoms
T
__________ is usually associated with Clostridium perfringens
Corned beef (temperature abused)
Clostridium perfringens is normally associated with _____ outbreaks
large
Give me some characteristics of C.perfringens:
- gram +
- motile
- rod-shaped
- sporeforming / can form small chains
- anaerobic but can tolerate some oxygen
Vegetative cells are ______ to heat (pasteurization) but spores are very heat _______ and can survive boiling for several hours
sensitive
resistant
C.perfringens grows from _____ C but its optimal temperature is at ___C
10-52
45
C.perfringens lack ______ synthesis ability, therefore they more commonly grow on high-protein foods (cooked meat products)
amino acid
In foods the most important factors (4) contributing to a C.perfringens outbreak are:
1) cooking large volumes in advance
2) allowing it to cool slowly
3) holding for a long period of time
4) serving without reheating
Complete the steps:
1) in C.perfringens cooking kills vegetative cells but spores survive
2) ________________
3) ________________
large volumes of food provide an anaerobic environment
slow cooling provides the temperature for spores to germinate and multiply
What is the #1 food type involved in Cp outbreaks?
Beef
T or F: some strains of Cp are harmless GI commensals
T
Cp vegetative cells can be found in :
- dust
- soil
- intestines of food-producing animals
- birds
- humans
- sewage
Some strains of Cp can cause gastrointestinal or tissue infections of various severities (give examples):
- necrotic tissue infections
- food poisoning
- antibiotic-associated diarrhea
- necrotizing enteritis
Talk about the symptoms of Cp:
- they appear 8-24 hours following the ingestion of a large number of viable cells
- symptoms include diarrhea and abdominal pain
- nausea, vomiting and fever can occur but are less common
What about the fatality rates of Cp:
fatalities are rare, but can occur among the very young, elderly, and sick
Symptoms of Cp generally resolve in ___h
24
Cp is a _____ disease and is seldom reported
mild
The virulence potential of Cp is based on its ability to produce various combinations of more than ___ different toxins and several __________________ (exoenzymes)
15
extracellular hydrolytic enzymes
Toxin coding genes can be located on ___________________, so several different pathotypes exist
mobile genomic elements
C.perfringens strains are classified into 5 toxinotypes __________ based on the production of 4 major toxins
A,B,C,D,E
ALPHA, BETA, EPSILONE AND L
The Cp toxins are secreted during ___________________
the exponential growth phase
Cp type A strains are associated with _________
food poisoning in humans
Toxins function to make conditions that favor infection such as (name 2):
1- disrupt host cell membranes to release nutrients for cell
2- hydrolytic enzymes break down complex nutrients into smaller units that can be imported into the cell, and utilized by bacteria
Cp synthesizes an enterotoxin (CPE) that is responsible for the__________________
gastrointestinal symptoms
Unlike other toxins, CPE is only produced during ______________
sporulation
CPE binds to enterocytes and creates pores that cause the release of large volumes of ___________ and ___________
water and nutrients
CPE is heat-_________
liable
T or F: When Cp has sporulated in the intestine, diarrhea ensures its passed into the environment, both are ideal for maximum future spread and survival
T
Explain all the steps involved in the pore formation and Calcium influx by CPE:
1) CPE binds transmembrane tight junction proteins using sequences at the CPE C terminus
2) CPE starts to form a prepore large-complex formation
3) CPE joins with other molecules of CPE to form a highly-stable complex
4) Formation of this complex is dependent upon the presence of an intact N terminus
5) With an intact N terminus and putative TMD, the CPE large complex can undergo the conformational changes necessary for insertion into the membrane
6) This protects the complex from proteases and also allows the penetration of the phospholipid bilayer of enterocytes, causing the influx of Ca 2+ into the cell
7) Ca2+ influx initiates cell death pathways
Presence of Cp spores in food is ___________
Very common
*however for gastroenteritis, viable cells must be present in high numbers, therefore if numbers are kept low, the food is fine
How do you prevent a high number of Cp viable cells in food? (4)
- proper sanitation
- cooking food to highest temperature possible
- food should be cooled quickly and uniformly
- food stored for a long time, should be re-heated quickly and uniformly, and be kept hot during serving (above 60C)
What are the key characteristics the genus Bacillus?
- gram positive
- spore-forming
- rod-shaped
- aerobic
Why outbreaks of Bc are highly underestimated?
Because they are moderate in severity, and have symptoms similar to those caused by other food-borne pathogens
Bc is widespread in nature and is frequently isolated from _________ and _________
soil
growing plants
Bc is rapidly spread from grass to ______________ and into raw milk
cows’ udders
T or F: Bc spores can survive milk pasteurization, after germination they can cause problems in dairy product
T
Most strains of Bc are unable to grow at _____________________ (below 10∘C), although _______________ strains can grow at temperatures as low as 4∘C
refrigerator temperature
psychrotolerant
T or F: If Bc contaminated milk is on the market it generally only causes one or two cases of illness (and is not identified as an outbreak)
T
T or F: Towards the end of milk’s shelf life there is often enough Bc to cause illness
T
The ___________ produced by Bc cause off flavors and people consume little if any of the milk
proteases
Bc has the potential to produce 2 toxins, an _________ and a _____________
emetic (vomit-inducing)
diarrheal enterotoxin
Give me the characteristics of the emetic toxin produced by Bc:
- Heat stable (like S.aureus toxin)
- Acts rapidly (0.5-6hr) after ingestion
- Produced by cells growing in the food
- Stimulates the vagus nerve to initiate vomiting
Give me the characteristics of the diarrheal enterotoxin produced by Bc:
- Several different types of heat-liable toxins
- Acts more slowly (6-14hr) after ingestion
- Produced by vegetative cell growth in the small intestine
- Mode of action not well understood, but induces diarrhea by stimulating cAMP system (like Vibrio cholerae).
What are the main symptoms associated with the Bc emetic toxin?
- nausea
- vomiting
- malaise
What are the foods most frequently implicated with the emetic toxin produced by Bc?
- Fried or cooked rice
- Pasta
- Pastry
- Noodles
What are the main symptoms associated with the Bc diarrheal enterotoxin?
- watery diarrhea
- occasional nausea
- abdominal pain
What are the foods most frequently implicated with the diarrheal enterotoxin produced by Bc?
- meat products
- soups
- vegetables
- puddings/sauces
- milk and milk products
What are the factors that contribute to Bc illness:
- improper holding temperature
- contaminated equipment
- inadequate cooking
- poor personal hygiene
T or F: Cooking does not destroy Bc spores, so the best strategy is to make sure that spores do not germinate and cells do not grow
T
Since some Bc can grow at 4C food should not be refrigerated for ___________________(well in advance preparation should be avoided)
long periods of time
T or F: 3 species of Bacillus (Bacillus thuringiensis, Bacillus anthracis and Bacillus cereus) have huge differences between their impacts on human health
T
___________ is the cause of the acute and often lethal disease anthrax
B. anthracis
____________ is extensively used as a biological control for insects, because of its ability to produce protein crystals with insecticidal activity
B. thuringiensis
_________ causes food-borne illness, but some strains have also been developed as biological control agents in the suppression of fungal and crop diseases
B. cereus
Phylogenetic studies also indicate that B. ________ and B. ______ are essentially the same
thuringiensis
cereus
It is difficult to tell B. ________ apart, except through biochemical tests
anthracis
C.perfringens review:
- C.perfringens is an _________ spore-forming bacteria commonly found on meat products
- The toxicoinfection toxin is released when the vegetative cells release their spores in the _____
- Improper _______ or ________ is the major cause of C.perfringens type A toxicoinfection
- The ____ gene encodes the enterotoxin
anaerobic
gut
heating or cooling
Cpe
B.cereus review:
- it is a _________
- is a normal inhabitant of soil and is isolated from a variety of foods
- two different toxins can cause _____ or _______ type of food-associated illness
- Desserts, meat, and dairy are usually associated with ________, while rice and pasta are associated with emetic illness
- Some strains will grow at _____ temperature
sporeformer
emetic/diarrheal
diarrhea
emetic
refrigeration
__________ and _____________ can be toxicoinfections but the defining factor is that large numbers of cells must be ingested for symptoms
V.cholerae and enterotoxigenic E.coli
