IIA. Systemic Bacteriology | 1. Staphylococcus genus Flashcards
I. Basics
1. Give the classification of pyogenic cocci
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I. Basics
1. Give the classification of Staphylococcus genus
I. Basics
1. What is the microscopic morphology of Staphylococcus genus?
- Gram positive cocci of uniform size (1 μm diameter)
- Arranged in grape-like clusters (but also found single or in pairs) „staphyle” meaning bunch of grapes
- Non-motile
- Non-spore forming
I. Basics
2. How should the culture for Staphylococcus genus be?
I. Basics
3. How should the biochemical test for Staphylococcus genus be?
- Catalase positive !! (Streptococci : catalase negative)
I. Basics
4. What are the 3 important species of medical importance of Staphylococcus genus?
- Staphylococcus aureus
- Staphylococcus epidermidis
- Staphylococcus saprophyticus
I. Basics
5. How is S. aureus distinguished from the other species?
- Coagulase production (CPS; coagulase positive Staphylococcus) coagulase test
- Mannitol fermentation
- Haemolysis of RBCs - S. aureus produces β-hemolytic colonies on blood agar
I. Basics
6. How do we grow S. aureas?
S. aureus grow on blood agar producing golden yellow pigment aureus = golden… butter consistency
(CNS: coagulase negative)
I. Basics
7. How should we perform biochemical test for Staphylococcus genus?
● Coagulase + : Staphylococcus aureus
● Coagulase - : other Staphylococcus species (“CNS-coagulase negative staphylococci”)
● Tube coagulase test: the examined strain is inoculated into rabbit plasma and after incubation the coagulase will coagulate the plasma free coagulase
II. S. aureas
1. Describe the Microscopic morphology of S.aureas
Gram-positive cocci, in grape-like structures
II. S. aureas
2. Describe the Colony morphology of S.aureas
- Rather big, round colonies; buttery consistency
- Golden pigment (staphyloxanthin)
- β-hemolysis on blood agar
II. S. aureas - virulence factors
3A. What are the cell bound factors of S.aureas?
II. S. aureas - virulence factors
3B. What is the role of Protein A as a cell bound factor of S.aureas?
- acts as an Fc receptor binding Fc portion of IgG
- inhibition pf phagocytosis
- biofilm formation!
II. S. aureas - virulence factors
3C. What is the role of Coagulase as a cell bound factor of S.aureas?
masking fibrin coat
II. S. aureas - virulence factors - Enzymes for invasion and spread
4A. What are the 4 enzymes of S.aureas that are responsible for invasion and spread?
- Hyaluronidase
- breaks down proteoglycans in connective tissue - Fibrinolysin (=staphylokinase)
- lyses fibrin clots (similar to streptokinase) - Lipase
- degradation of fats and oils (facilitation of colonization of sebaceous glands) - Nuclease (DNAse)
II. S. aureas - virulence factors - Enzymes for invasion and spread
4B. What is the role of Hyaluronidase?
breaks down proteoglycans in connective tissue
II. S. aureas - virulence factors - Enzymes for invasion and spread
4C. What is the role of staphylokinase?
Fibrinolysin (=staphylokinase)
* lyses fibrin clots (similar to streptokinase)
II. S. aureas - virulence factors - Enzymes for invasion and spread
4D. What is the role of Lipase?
degradation of fats and oils (facilitation of colonization of sebaceous glands)
II. S. aureas - virulence factors - Enzymes for invasion and spread
5A. What are the cytotoxins produced by S. aureas?
- Hemolysins (alpha, beta, gamma, delta)
- Leukocidins
II. S. aureas - virulence factors
5B. What is the role of Hemolysins produced by S. aureas?
Hemolysins (alpha, beta, gamma, delta)
- they are hemolytic toxins that destroy red blood cells,
neutrophils, macrophages, and platelets
II. S. aureas - virulence factors
5C. What is the role of Leukocidins produced by S. aureas?
- destroy leukocytes (is the cause of necrotic lesions involving the skin or mucosa, including necrotic hemorrhagic pneumonia)
- Panton-Valentine leukocidin (PVL)
- strong association with CA-MRSA
- no hemolytic activity
II. S. aureas - virulence factors
6A. What are the exotoxins produced by S. aureas?
- TSST-1 (toxic shock syndrome toxin)
- Exfoliative toxin
- Enterotoxins (A-F)
II. S. aureas - virulence factors - exotoxins
6B. What are the features of TSST-1 (toxic shock syndrome toxin) produced by S.aureas?
- Superantigen
- often associated with tampon use
- localised infection (vagina or wound), but toxin can go through mucosa and can lead to MOF
- characteristic rash (sunburn like) usually seen at onset
II. S. aureas - virulence factors - exotoxins
6B. What are the features of Exfoliative toxin produced by S.aureas?
- Superantigen!
- SSSS = staphylococcal scalded skin syndrome (Ritter disease)
- protease activity of the exfoliative toxins causes peeling of the skin * no inflammation (important in diagnosis!)
- mainly in small children