PowerPoint 5:Staphyloccocus Aureus Flashcards
How does food intoxication occur?
Ingestion of food which had a pre-formed toxin
Do symptoms occur quickly?
Yes, usually 30 min after ingestion
Are febrile symptoms present?
No
Is it motile?
No
Does it have a capsule?
No
Does it have form spores?
No
Is it sensitive to heat treatments?
Yes.
66°C for 12 minutes
72°C for 15 seconds
What is their aerobic classification?
Facultative aerobes.
Grow better in oxygen.
What is their “temperature” classification?
Mesophiles
What temperature can Staph grow at?
7°C - 48°C
What temperature can they rapidly grow at?
20°C-37°C
What Aw can they grow at?
Low (0.86)
What pH can they grow at?
Low (pH 4.8)
What salt and sugar concentrations can it grow at?
High salt and sugar concentrations
Can they grow under adverse conditions?
Yes
Are they good competitors against other organisms?
No
What illnesses can it cause?
Skin infections Endocarditis Toxic shock syndrome Necrotizing pneumonia Mastitis
What percentage of the S. aureus genome is made of mobile genetic elements that can be transferred ?
20%
T/F : Enterotoxin is mainly found in mobile genetic elements?
T
How many prophage genomes are carried?
1-4
Where are the enterotoxins found?
Phage genome
Is illness caused by ingestion of the organism?
No
What is an endotoxin?
Toxin associated structurally with the bacterial cell (LPS)
Can an exotoxin be intracellular and injected directly into a eukaryotic cell?
Yes, but it is secreted by the bacteria producing it
What are exfoliative exotoxins?
dermolytic exotoxin produced exclusively by s. aureus and causes impetigo or scaled skin.
T/F All enterotoxins are also exotoxins
T
what type of eneterotoxin does it produce?
A B C D E F G H I J
What is the toxin that causes toxic shock syndrome?
Endotoxin F
Enterotoxin B
In what phase are the enterotoxins formed?
Exponential growth phase
What can inhibit the production of enterotoxins?
Glucose
Are enterotoxins involved in Quorum Sensing?
Yes probably
Why is staph. aureus toxin special?
Very heat stable - not destroyed by boiling or canning
How many patients (in percentage) carry s. aureus with enterotoxin genes yet they don’t get the disease?
50%
What does the toxin stimulate?
Vagus and sympathetic nerves
Who are the main reservoir?
People
T/F It can be passed by direct contact and respiratory droplets
T
Is Staph. aureus able to invade our cells and live intracellularly?
Yes
Can it be resistant to metals and antibiotics?
Yes
Is it able to survive a variety of extreme environments?
Yes
What disease can it cause in cows?
Bovine mastitis
What is the optimal temperature for their growth?
37-40 degress celsius
How many hours does it require to produce sufficient toxins in the ideal temperature?
3 hours
Does it have a quick onset?
Yes, 30 minutes
How long does it take for recovery?
12-48 hours
Is it self-limiting?
Yes
Is there any fever?
No
What is the purified toxin considered?
Bio terrorism agent
What is the infectious dose?
10^5 cells / g
What is the infectious dose of the toxin?
1 ng/g
Some strains are resistant to what?
Methicillin-Resistant Sa (MRSA)
-carry the macA gene
What disease does MRSA cause?
- soft tissue and skin infections
- necrotizing fascitis
Summary
- toxins are an important factor
- reside on skin, nare, and hair of humans and animals
- any foodstuff involving human contact, or is from a food producing animal can be potentially infected
- the result of the Sa contamination will depend on the genetic makeup of the particular organism
