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
