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AA Microbio Semifinal > IIA. Systemic Bacteriology | 1. Staphylococcus genus > Flashcards

IIA. Systemic Bacteriology | 1. Staphylococcus genus Flashcards

1
Q

I. Basics
1. Give the classification of pyogenic cocci

A

1

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1
Q

I. Basics
1. Give the classification of Staphylococcus genus

A
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2
Q

I. Basics
1. What is the microscopic morphology of Staphylococcus genus?

A
  • 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
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3
Q

I. Basics
2. How should the culture for Staphylococcus genus be?

A
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4
Q

I. Basics
3. How should the biochemical test for Staphylococcus genus be?

A
  • Catalase positive !! (Streptococci : catalase negative)
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5
Q

I. Basics
4. What are the 3 important species of medical importance of Staphylococcus genus?

A
  • Staphylococcus aureus
  • Staphylococcus epidermidis
  • Staphylococcus saprophyticus
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6
Q

I. Basics
5. How is S. aureus distinguished from the other species?

A
  • Coagulase production (CPS; coagulase positive Staphylococcus) coagulase test
  • Mannitol fermentation
  • Haemolysis of RBCs - S. aureus produces β-hemolytic colonies on blood agar
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7
Q

I. Basics
6. How do we grow S. aureas?

A

S. aureus grow on blood agar producing golden yellow pigment aureus = golden… butter consistency

(CNS: coagulase negative)

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8
Q

I. Basics
7. How should we perform biochemical test for Staphylococcus genus?

A

● 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

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9
Q

II. S. aureas
1. Describe the Microscopic morphology of S.aureas

A

Gram-positive cocci, in grape-like structures

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10
Q

II. S. aureas
2. Describe the Colony morphology of S.aureas

A
  • Rather big, round colonies; buttery consistency
  • Golden pigment (staphyloxanthin)
  • β-hemolysis on blood agar
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11
Q

II. S. aureas - virulence factors
3A. What are the cell bound factors of S.aureas?

A
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12
Q

II. S. aureas - virulence factors
3B. What is the role of Protein A as a cell bound factor of S.aureas?

A
  • acts as an Fc receptor binding Fc portion of IgG
  • inhibition pf phagocytosis
  • biofilm formation!
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13
Q

II. S. aureas - virulence factors
3C. What is the role of Coagulase as a cell bound factor of S.aureas?

A

masking fibrin coat

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14
Q

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?

A
  1. Hyaluronidase
    - breaks down proteoglycans in connective tissue
  2. Fibrinolysin (=staphylokinase)
    - lyses fibrin clots (similar to streptokinase)
  3. Lipase
    - degradation of fats and oils (facilitation of colonization of sebaceous glands)
  4. Nuclease (DNAse)
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15
Q

II. S. aureas - virulence factors - Enzymes for invasion and spread
4B. What is the role of Hyaluronidase?

A

breaks down proteoglycans in connective tissue

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16
Q

II. S. aureas - virulence factors - Enzymes for invasion and spread
4C. What is the role of staphylokinase?

A

Fibrinolysin (=staphylokinase)
* lyses fibrin clots (similar to streptokinase)

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17
Q

II. S. aureas - virulence factors - Enzymes for invasion and spread
4D. What is the role of Lipase?

A

degradation of fats and oils (facilitation of colonization of sebaceous glands)

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18
Q

II. S. aureas - virulence factors - Enzymes for invasion and spread
5A. What are the cytotoxins produced by S. aureas?

A
  1. Hemolysins (alpha, beta, gamma, delta)
  2. Leukocidins
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19
Q

II. S. aureas - virulence factors
5B. What is the role of Hemolysins produced by S. aureas?

A

Hemolysins (alpha, beta, gamma, delta)
- they are hemolytic toxins that destroy red blood cells,
neutrophils, macrophages, and platelets

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20
Q

II. S. aureas - virulence factors
5C. What is the role of Leukocidins produced by S. aureas?

A
  1. destroy leukocytes (is the cause of necrotic lesions involving the skin or mucosa, including necrotic hemorrhagic pneumonia)
  2. Panton-Valentine leukocidin (PVL)
    - strong association with CA-MRSA
    - no hemolytic activity
21
Q

II. S. aureas - virulence factors
6A. What are the exotoxins produced by S. aureas?

A
  1. TSST-1 (toxic shock syndrome toxin)
  2. Exfoliative toxin
  3. Enterotoxins (A-F)
22
Q

II. S. aureas - virulence factors - exotoxins
6B. What are the features of TSST-1 (toxic shock syndrome toxin) produced by S.aureas?

A
  1. Superantigen
  2. often associated with tampon use
  3. localised infection (vagina or wound), but toxin can go through mucosa and can lead to MOF
  4. characteristic rash (sunburn like) usually seen at onset
23
Q

II. S. aureas - virulence factors - exotoxins
6B. What are the features of Exfoliative toxin produced by S.aureas?

A
  • 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
24
Q

II. S. aureas - virulence factors - exotoxins
6B. What are the features of Enterotoxins (A-F) produced by S.aureas?

A
  • Superantigens!
  • heat stable exotoxins which cause food poisoning, resulting in nausea, vomiting and diarrhoea
  • resistant to cooking (100 oC, 30 min)
  • C, D: dairy products
25
Q

II. S. aureas
7. What are S. aureas skin infections (see pic in both answer and question)?

26
Q

II. S. aureas
8. How are wound infections caused by S.aureas?

A
  • burns, postoperational, trauma
  • from the skin flora
27
Q

II. S. aureas - invasive infections
9A. What are the invasive infections caused by S.aureas?

28
Q

II. S. aureas - invasive infections
9B. What is Osteomyelitis?

A

hematogenous spread or superinfection of trauma

29
Q

II. S. aureas - invasive infections
9C. What is Sepsis?

A
  • half of all cases of inpatient sepsis
  • in immunocompromised patients
30
Q

II. S. aureas - invasive infections
9D. What is Endocarditis?

A
  • Following heart surgery (esp. valve replacement)
  • 50% letality
31
Q

II. S. aureas - invasive infections
9E. What is Pneumonia?

A

predominantly affects people with underlying lung disease including those on mechanical ventillation

32
Q

II. S. aureas - invasive infections
9F. What is Meningitis?

A

accounts for 1-9% of cases of bacterial meningitis

33
Q

II. S. aureas
10. Explain laboratory identification for staphylococci?

34
Q

II. S. aureas
11. What are the features of MRSA (methicillin-resistant S. aureus)?

A
  • penicillin resistance: ~ 90%
35
Q

II. S. aureas
12. Where do usually find S.aureas?

A
  • frequently found in normal flora of skin and nasal mucosa
36
Q

II. S. aureas
13. How do we prevent the spread of S.aureas?

A
  • Hand hygiene!
  • Environmental cleaning / disinfection
    +) iodine, hexachlorophene
  • Personal protective equipments
  • Isolation of patients
  • Regular screening of medical staff
37
Q

II. S. aureas
14. How do we decolonize the S.aureas?

A
  • Intranasal mupirocin
  • Resistance is developing!
38
Q

II. S. aureas
15. How do we treat the S.aureas?

A
  • Gastroenteritis is self-limiting
  • Penicillin → Nafcillin (if not MRSA)
  • Vancomycin if penicillin resistant
39
Q

III. Staphylococcus epidermidis
1. What is the microscopic morphology of S. epidermis?

A

Gram-positive cocci, in grape-like structures

40
Q

III. Staphylococcus epidermidis
2. What is the colony morphology of S. epidermis?

A
  • white pigment
  • no hemolysis
41
Q

III. Staphylococcus epidermidis
3. What is the reservoir of S. epidermis?

A
  • Normal skin flora
  • Can contaminate blood cultures
42
Q

III. Staphylococcus epidermidis
4. What are the diseased caused by S. epidermis?

A
  • Endocarditis of artificial heart valves in IV drug users
  • Catheter infection
  • Prosthetic device infection
43
Q

III. Staphylococcus epidermidis
5. What are the treatments for S. epidermis?

A

Vancomycin

44
Q

III. Staphylococcus epidermidis
2. What is the colony morphology of S. epidermis?

A
  • white pigment
  • no hemolysis
45
Q

III. Staphylococcus epidermidis
2. What is the colony morphology of S. epidermis?

A
  • white pigment
  • no hemolysis
46
Q

III. Other coagulase negative staphylococci
1. Name 5 Other coagulase negative staphylococci

A
  1. S. saprophyticus
  2. S. hominis
  3. S. haemolyticus
  4. S. lugdunensis
47
Q

III. Other coagulase negative staphylococci
2. What are the features of S. saprophyticus? (IMPORTANT)

A
  • second frequent in UTIs after E. coli, esp. in young women („honeymoon cystitis”)
  • white pigment, no hemolysis
  • differentiation from S. epid.: novobiocin resis
  • Th: ciprofloxacin
48
Q

III. Other coagulase negative staphylococci
3. What are the features of S. hominis? (IMPORTANT)

A

skin flora; opportunistic pathogen

49
Q

III. Other coagulase negative staphylococci
4. What are the features of S. haemolyticus? (IMPORTANT)

A

skin flora; opp. pathogen; inserted devices

50
Q

III. Other coagulase negative staphylococci
5. What are the features of S. lugdunensis? (IMPORTANT)

A

agressive endocarditis

51
Q

III. Other coagulase negative staphylococci
5. What are the features of S. lugdunensis? (IMPORTANT)

A

agressive endocarditis

AA Microbio Semifinal (99 decks)

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