Intoxications Flashcards
Foodborne intoxication
Occurs from ingestion of a food containing a preformed toxin
Why have S. aureus outbreaks decreased
Better use of refrigeration and improved sanitary practices
S aureus key features
- Gram positive
- Cocci
- Non-motile, noncapsular
- Non-spore forming
- Heat sensitive
- Facultative anaerobes
- Mesophiles
- Low Aw
- Low pH
- Poor competitors
How many housekeeping genes are found in S aureus
7
If a group of sequence types share at least 5-7 alleles, they can be defined as…
A clonal complex
Explain the restriction modification system of S. aureus
The accessory genome has a lot of mobile genetic elements that can be transferred horizontally, but the system prevents HGT from happening between clonal complexes
Phage genomes of S. aureus have…
Enterotoxins
Enterotoxin
Acts on GI tract
Endotoxin
Structurally associated with bacterial LPS
Exotoxin
Usually secreted into ECF, can be intracellular or injected into eukaryotic cells
Exfoliative toxins
Dermolytic exotoxins produced exclusively by S. aureus that cause impetigo or scaled skin syndrome
All Sa enterotoxins are…
Exotoxins
What toxins cause TSS
F (endotoxin) and B
When are toxins made in S. aureus
Exponential growth phase
Enterotoxin production can be inhibited by…
Glucose
How much of the gut does Sa carrying the enterotoxin gene inhabit
50% of non-enteritis patients
What is the main source of environmental Sa
Humans
What does Sa infection cause in cows
Mastitis
What can happen when humans carrying Sa infect animals
Repeated exposure causes human strains to adapt to animals, which can eventually reinfect humans
However the strains are unknown to humans so they may be more pathogenic
Common foods contaminated with Sa
Ground beef, salmon, oyster, ground turkey
Infectious dose of Sa toxin
1ng/g (less than 10^5cells/g)
Four faces of C botulinum
Intoxication, infant botulism, wound botulism, bioterrorism
Infant botulism
Ingestion and intestinal proliferation of the organism, internal production of toxin
Wound botulism
Deep wound results in anaerobic environment
How is C botulinum defined
All strains are toxic
Cb group 3 toxins
Type C and D (animal)
Cb group 2 toxins
Type E, non-proteolytic B and F
Cb group 4 toxins
Type G
Cb group 1 toxins
Type A, proteolytic B and F
Nonproteolytic BoNT
Stomach acid cleaves it to activate
Proteolytic BoNT
Bacteria produce a protease that activates it
Which BoNT toxin types interfere with SNARE protein formation
B, D, F, G
What BoNT toxin types interfere with membrane fusing
A, C, E
What BoNT toxin type interferes with release of neurotransmitter
C
What Cb strains infect humans
Group 1 and 2
Why is trypsin added in Cb detection
To determine if it is proteolytic or non proteolytic
The BoNT toxin can be carried on…
A chromosome or plasmid
Describe the Cb genome
Circular chromosome, G/C content of 27-28%
What is a major concern of the mobility of the BoNT toxin genes
C. difficile getting it through HGT
Where is Cb found
Ubiquitous in soils
How does Cb survive
Secretes hydrolytic enzymes and then transports the stuff it degrades into the cell (does not have own genes for AA synthesis)
If Cb is ubiquitous, how come a lot of people are not infected
It is outcompeted by other organisms so it can’t produce to toxin
What is a common cause of food botulism
Home canning of fruits and veggies and fermented fish
What toxin types are associated with fish
E
What toxin types are associated with fruits and vegetables
A and B
