16 - Toxico-Infections

Question 1

Key characteristics common among toxico-infections for spore formers:

Answer 1

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

Question 2

Key characteristics common among toxico-infections for gram negative bacteria :

Answer 2

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

Question 3

T or F: Toxins of both groups (spore formers and gram - bacteria) cause gastroenteritis symptoms

Answer 3

T

Question 4

__________ is usually associated with Clostridium perfringens

Answer 4

Corned beef (temperature abused)

Question 5

Clostridium perfringens is normally associated with _____ outbreaks

Answer 5

large

Question 6

Give me some characteristics of C.perfringens:

Answer 6

• gram +
• motile
• rod-shaped
• sporeforming / can form small chains
• anaerobic but can tolerate some oxygen

Question 7

Vegetative cells are ______ to heat (pasteurization) but spores are very heat _______ and can survive boiling for several hours

Answer 7

sensitive

resistant

Question 8

C.perfringens grows from _____ C but its optimal temperature is at ___C

Answer 8

10-52

45

Question 9

C.perfringens lack ______ synthesis ability, therefore they more commonly grow on high-protein foods (cooked meat products)

Answer 9

amino acid

Question 10

In foods the most important factors (4) contributing to a C.perfringens outbreak are:

Answer 10

1) cooking large volumes in advance
2) allowing it to cool slowly
3) holding for a long period of time
4) serving without reheating

Question 11

Complete the steps:

1) in C.perfringens cooking kills vegetative cells but spores survive
2) ________________
3) ________________

Answer 11

large volumes of food provide an anaerobic environment

slow cooling provides the temperature for spores to germinate and multiply

Question 12

What is the #1 food type involved in Cp outbreaks?

Answer 12

Beef

Question 13

T or F: some strains of Cp are harmless GI commensals

Answer 13

T

Question 14

Cp vegetative cells can be found in :

Answer 14

• dust
• soil
• intestines of food-producing animals
• birds
• humans
• sewage

Question 15

Some strains of Cp can cause gastrointestinal or tissue infections of various severities (give examples):

Answer 15

• necrotic tissue infections
• food poisoning
• antibiotic-associated diarrhea
• necrotizing enteritis

Question 16

Talk about the symptoms of Cp:

Answer 16

• 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

Question 17

What about the fatality rates of Cp:

Answer 17

fatalities are rare, but can occur among the very young, elderly, and sick

Question 18

Symptoms of Cp generally resolve in ___h

Answer 18

24

Question 19

Cp is a _____ disease and is seldom reported

Answer 19

mild

Question 20

The virulence potential of Cp is based on its ability to produce various combinations of more than ___ different toxins and several __________________ (exoenzymes)

Answer 20

15

extracellular hydrolytic enzymes

Question 21

Toxin coding genes can be located on ___________________, so several different pathotypes exist

Answer 21

mobile genomic elements

Question 22

C.perfringens strains are classified into 5 toxinotypes __________ based on the production of 4 major toxins

Answer 22

A,B,C,D,E

ALPHA, BETA, EPSILONE AND L

Question 23

The Cp toxins are secreted during ___________________

Answer 23

the exponential growth phase

Question 24

Cp type A strains are associated with _________

Answer 24

food poisoning in humans

Question 25

Toxins function to make conditions that favor infection such as (name 2):

Answer 25

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

Question 26

Cp synthesizes an enterotoxin (CPE) that is responsible for the__________________

Answer 26

gastrointestinal symptoms

Question 27

Unlike other toxins, CPE is only produced during ______________

Answer 27

sporulation

Question 28

CPE binds to enterocytes and creates pores that cause the release of large volumes of ___________ and ___________

Answer 28

water and nutrients

Question 29

CPE is heat-_________

Answer 29

liable

Question 30

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

Answer 30

T

Question 31

Explain all the steps involved in the pore formation and Calcium influx by CPE:

Answer 31

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

Question 32

Presence of Cp spores in food is ___________

Answer 32

Very common *however for gastroenteritis, viable cells must be present in high numbers, therefore if numbers are kept low, the food is fine

Question 33

How do you prevent a high number of Cp viable cells in food? (4)

Answer 33

- 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)

Question 34

What are the key characteristics the genus Bacillus?

Answer 34

- gram positive - spore-forming - rod-shaped - aerobic

Question 35

Why outbreaks of Bc are highly underestimated?

Answer 35

Because they are moderate in severity, and have symptoms similar to those caused by other food-borne pathogens

Question 36

Bc is widespread in nature and is frequently isolated from _________ and _________

Answer 36

soil | growing plants

Question 37

Bc is rapidly spread from grass to ______________ and into raw milk

Answer 37

cows' udders

Question 38

T or F: Bc spores can survive milk pasteurization, after germination they can cause problems in dairy product

Answer 38

T

Question 39

Most strains of Bc are unable to grow at _____________________ (below 10∘C), although _______________ strains can grow at temperatures as low as 4∘C

Answer 39

refrigerator temperature | psychrotolerant

Question 40

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)

Answer 40

T

Question 41

T or F: Towards the end of milk's shelf life there is often enough Bc to cause illness

Answer 41

T

Question 42

The ___________ produced by Bc cause off flavors and people consume little if any of the milk

Answer 42

proteases

Question 43

Bc has the potential to produce 2 toxins, an _________ and a _____________

Answer 43

emetic (vomit-inducing) | diarrheal enterotoxin

Question 44

Give me the characteristics of the emetic toxin produced by Bc:

Answer 44

- 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

Question 45

Give me the characteristics of the diarrheal enterotoxin produced by Bc:

Answer 45

- 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).

Question 46

What are the main symptoms associated with the Bc emetic toxin?

Answer 46

- nausea - vomiting - malaise

Question 47

What are the foods most frequently implicated with the emetic toxin produced by Bc?

Answer 47

- Fried or cooked rice - Pasta - Pastry - Noodles

Question 48

What are the main symptoms associated with the Bc diarrheal enterotoxin?

Answer 48

- watery diarrhea - occasional nausea - abdominal pain

Question 49

What are the foods most frequently implicated with the diarrheal enterotoxin produced by Bc?

Answer 49

- meat products - soups - vegetables - puddings/sauces - milk and milk products

Question 50

What are the factors that contribute to Bc illness:

Answer 50

- improper holding temperature - contaminated equipment - inadequate cooking - poor personal hygiene

Question 51

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

Answer 51

T

Question 52

Since some Bc can grow at 4C food should not be refrigerated for ___________________(well in advance preparation should be avoided)

Answer 52

long periods of time

Question 53

T or F: 3 species of Bacillus (Bacillus thuringiensis, Bacillus anthracis and Bacillus cereus) have huge differences between their impacts on human health

Answer 53

T

Question 54

___________ is the cause of the acute and often lethal disease anthrax

Answer 54

B. anthracis

Question 55

____________ is extensively used as a biological control for insects, because of its ability to produce protein crystals with insecticidal activity

Answer 55

B. thuringiensis

Question 56

_________ causes food-borne illness, but some strains have also been developed as biological control agents in the suppression of fungal and crop diseases

Answer 56

B. cereus

Question 57

Phylogenetic studies also indicate that B. ________ and B. ______ are essentially the same

Answer 57

thuringiensis | cereus

Question 58

It is difficult to tell B. ________ apart, except through biochemical tests

Answer 58

anthracis

Question 59

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

Answer 59

anaerobic gut heating or cooling Cpe

Question 60

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

Answer 60

sporeformer emetic/diarrheal diarrhea emetic refrigeration

Question 61

__________ and _____________ can be toxicoinfections but the defining factor is that large numbers of cells must be ingested for symptoms

Answer 61

V.cholerae and enterotoxigenic E.coli