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16 Cards in this Set
- Front
- Back
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What is unique about S. aureus toxin?
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It is not destroyed by heating or canning
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Name characteristics of S. aureus
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Cocci shaped, organized in clusters, gram +, catalase positive, mannitol salt fermentation +, (s.aureus)coagulase +, non sporeforming, facultative anaerobe, non-motile, enterotoxin +, hemolysis +, thermostable DNAse, Yellow colonies,
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What are the diseases caused by S. aureus?
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Skin infections (pimples, impetigo), nosocomial infections, respiratory infections, toxic shock syndrome, endocarditis (inside organs), foodbourne intoxications, halotolerant (up to 10% -- most of any pathogen), can grow in Aw of 0.86, phychrophile
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What are the disease characteristics of S. aureus?
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food intoxication, 1-6 hour incubation time, 10>5 CFU/g infectious dose, nausea, severe vomiting, severe abdominal cramps, diarrhea, NOOO FEVER!, Self limiting
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Virulence Factors for S. aureus
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Enterotoxins--
Composed of Two Subunits (C-Terminal causes emesis) Many Different Types: A, b, c1, c3, c3, d, e, g, h, i, j (named in order of discovery) Belong to superantigen group of toxins Extremely resistant to heat, pH and proteolysis Toxin dose is 1 ng Affected Cells: Neural receptors in abdomen Enterocytes Intestinally Associated Immune Cells |
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Where can S. aureus be found in nature?
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Nose, throat and skin of Humanoids
Warm bloded animals (Low #'s) (PIERRE AND LUCY) Persist in air, dust and equipment in food processing environment Sewage |
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What are associated foods with Staph aureus infection?
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Deli meat, fermented foods, ham, salads (potato, turkey, chicken), tacos, burritos, canned mushrooms, smoked oysters, dairy
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What foods have highest prevalence of Staph aureus?
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Blue crabmeat, Big game, pork sausage, deli salads
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Name selective agents in S. aureus culture testing
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Potassium Tellurite, LiCl
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Name differential ingredients in S. aureus culture testing.
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Potassium tellurite, Egg yolk (halo and precip)
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How can S aureus be controlled so taht it does not produce enterotoxin?
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Prevent growth by keeping food below 5C or above 50C
Good GMP/personal hygeine Monitor pH of fermented foods ot ensure active fermentation If staph is used as starter culture, make sure it is enterotoxin free |
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What are confirmatory steps in S. aureus detection?
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Coagulase and thermonuclease test
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What is special about toxic shock syndrome toxin?
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It is considered an exotoxin that does not cause vomiting as the other toxins do. It is called Toxic shock syndrome toxin 1
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Which enterotoxin strain produces the greatest amount of toxin? Easiest to detect? Which go undetected the most?
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B and C produce the most in amount up to 350µg/mL
A, D, and E are easily detected by PFGE D & J go undetected the most |
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What genes regulate expression of the enterotoxin?
Which strain is not regulated by agr (most common)? |
agr (expressed differently by each strain) acessory gene regulator, sar (staph acessory regulator), and sae (s aureus exoprotein expression)
Strain A is not regulated by agr, which is why it is expressed prior to the other enterotoxins. |
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The enterotoxins are mostly expressed during what phase?
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Late exponential and post exponential growth
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