Toxico-infections Flashcards
Common characteristics among spore forming toxico-infections
- Ingestion of large numbers of live vegetative cells
2. Vegetative cells of spore formers do not multiply in the GI tract (sporulate and release toxins)
Common characteristics among gram-negative bacteria toxico-infections
- Live cells are ingested in moderate numbers
- Gram negative cells rapidly multiply in GI tract
- Many cells die, releasing toxins
What is the growth temp of C. perfingens
10-52C, optimal at 45C
Why do C. perfringens grow on high protein foods
They lack amino acid synthesis ability
What are the 4 most important factors contributing to an outbreak of C. perfringens
- Cooking in large volumes in advance
- allowing it cool slowly
- holding for a long period of time
- serving without reheating
Describe a C. perfringens outbreak
- cooking kills vegetative cells, spores survive
- Large volumes of food provide anaerobic environment
- Slow cooling allows spores to germinate and multiply
Where are C. perfringens vegetative cells founds
Soil, dust, intestines of food-producing animals, birds
When do C. perfringens symptoms appear
8-24 hours (resolve in 24 hours)
What are symptoms of C. perfringens infection
Diarrhea, abd pain, nausea, vomiting
What is the virulence potential of C. perfringens based on
The ability of Cp to produce various combinations of more than 15 different toxins and several extracellular hydrolytic enzymes
What are the 5 toxinotypes of Cp and what are they based on
A,B,C,D and E
They are based on the production of 4 major toxins (alpha, beta, epilson, iota)
When are Cp toxins secreted
Exponential growth phase
What Cp strains are associated with food poisioning
Type A
What are 2 ways Cp toxins make conditions to favor infection
- Disrupt host cell membranes to release nutrients
2. Hydrolytic enzymes break down complex nutrients into smaller units that can be imported into the cell
What Cp toxin is responsible for the GI symptoms
CPE (enterotoxin, only produced during sporulation)
How does CPE work
It binds enterocytes and creates pores that cause the release of large volumes of water and nutrients
What allows Cp to spread in the environment
When it sporulates in the intestine, diarrhea ensures it is passed into the environment
What needs to happen for gastroenteritis to occur in Cp infection
Viable cells must be present in high numbers
4 Prevention methods of Cp infection
Proper sanitation, cooking food to highest temp possible, food should be cooled quickly and uniformly, food stored for a long time should be re-heated quickly and kept above 60C during serving
Where is Bc isolated from
soil and growing plants, raw milk (from grass contamination, can survive pasteurization)
At what temp can Bc not be grown
Below 10C (although some can grow in as low as 4C)
Why does Bc contaminated milk rarely cause illness
The proteases produced by Bc cause off flavors and people don’t consume a lot
What are the two toxins of Bc
Emetic (vomit-inducing) and diarrheal enterotoxin
How does the emetic toxin stimulate vomiting
It stimulates the vagus nerve
How does the diarrheal enterotoxin stimulate diarrhea
By stimulating cAMP system
Describe the infection process of Bc
Cooking kills the vegetative cells, the spores survive, spores are able to germinate and proliferation
**If vegetative cells are present, Bc isn’t competitive
4 factors that contribute to Bc illness
Improper holding temp
Contaminated equipment
Inadequate cooking
Poor personal hygiene
How to present Bc spore germination
Uniform quick chilling of food to 4C, or holding food above 60C (since some can grow at 4C , food should not be refrigerated for long periods of time)
B. anthracis
Cause of acute and lethal disease, anthrax
B. thuringiensis
Biological control of insects, because of its ability to produce protein crystals with insecticidal activity
B. cereus
Causes food borne illness, some strains have been developed as bio control agents in the suppression of fungal and crop diseases
What Bacillus strains are essentially the same based on phylogenetic studies
B. thuringiensis and B. cereus (emetic type)
What foods are associated with the diarrheal toxin
Desserts, meat and dairy
What foods are associated with the emetic toxin
Rice and pasta
What is the defining feature for V. cholera and ETEC to be toxicoinfections
Large numbers of cells must be ingested for symptoms
