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GPC usually in clusters but can be in tetrads.
Media appearance for each staph
1-3mm round, smooth, convex,glistening, opaque,entire edge, butyrous (butter like) consistency.
- aureus: may be yellow and have small zone of beta hemolysis.
- epidermidis: white colonies, usually nonhemolytic.
- saprophyticus: often pigmented - yellow, orange, tan
- MSA: is selective & differential media:
- aureus: ferments manitol, so colonies will change from red to yellow
- others staphs: Do NOT ferment manitol, so colonies stay red.
Pathogenicity for S. aureus
- Suppurative cutaneous infections
- Toxic shock syndrome
- Food poisoning
Pathogenicity for S epidermidis
Usually normal pathogen. Common contaminate. But those that are infectious:
Come from hospital acquired nosocomial UTI
Pathogenicity for S. saprophyticus
Causes UTI in young sexually active women or catheterized elderly men.
Tests for S aureus
- Coagulase, DNase, Catalase
- Ferments Manitol on MSA changing colony from red to yellow.
Tests for epidermidis & saprophyticus
- S. saprophyticus: resistant to Novobiocin
- S. epidermidis: suseptible to Novobiocin
3 Types of toxins for S. aureus
- Enterotoxins: Heat stable exotoxins that cause diarrhea & vomiting. Are performed in foods. Appear 2-8 hours after injestion. Resolve within 8 hrs.ie. toxic shock syndrome.
- Epidermolytic toxin, sloughing of the skin, widespread systemic immune response.
- Exfoliative toxin: Similar to TSST-1, but differnt site on skin.
- Cytolytic toxin: Extracellular factors that affect RBC's and WBC's
- alph: detryos RBC's,plt's,tissue
- beta: destroys RBC's
- Gamma: causes injury, less letahal
- Leukocidin: lethal to PMN's
Enzymes for Staph
- Coagulase: cuases coagulation of surroundings
- Hyaluronidase: hydrolyzes hyaluronic acin in connective tissue
- Lipase: aids colonization by actin gon sebaceous glands.
- FAME: breaks down anti-stahylococcal lipids made by the host.
How is Protein A produced from S. aureus?
- S. aureus cell wall
- Binds Fc portion of immunoglobulin (avoid phagocytosis.
- Chromagar MRSA