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Microbio Exam 2 > Staphylococci > Flashcards

Staphylococci Flashcards

1
Q

What are the main characteristics of staphylococcus?

A

Gram+
cocci
catalase+

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2
Q

What type of oxygen requirements does staphylococcus aureus need?

A

facultative anaerobe

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3
Q

What is catalase?

A

Reduces the potential of phagocytes to kill

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4
Q

What is coagulase?

A

coagulase binds prothrombin: fibrinogen is cleaved -> anti-phagocytic fibrin coating

  • The tissue-invasive potential of staphylococcal infections is directly proportional to coagulase production (S.aureus)
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5
Q

What is clumping factor?

A

fibrinogen-binding protein: cell surface proteins that bind to foreign materials (like sutures) and to extracellular matrix

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6
Q

What is protein A?

A

Anti-phagocytic, competes with neutrophils for Fc portion of opsonizing IgG’s

  • S aureus only (not other staphylococcal)
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7
Q

What is leukocidin?

A
  • secretion: inhibits phagocytosis by granulocytes by forming pores in phagosomal membranes, and kills phagocytes
  • Major factor in pus formation
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8
Q

What is staphylokinase?

A

converts plasminogen to plasmin, increasing invasion by digesting fibrin clots and cleaves C3b and IgG to inhibit phagocytosis

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9
Q

What is B-lactamase?

A
  • Enzymatic digestion of penicillins
  • (90% strains have plasmid-based antibiotic resistance)
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10
Q

What do hemolysins do?

A

lyse erythrocytes (lab phenomenon)

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11
Q

What type of hemolysis is complete erythrocyte lysis around all staphylococcus aureus colonies?

A

B-hemolysis

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12
Q

What type of staphylococcus experiences no hemolysis?

A

staphylococcus epidermidis

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13
Q

What is emphyema?

A

Collection of pus in a naturally- existing anatomical cavity (e.g. lungs)

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14
Q

What bacteria causes impetigo?

A

S. aureus

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15
Q

What are pyogenic infections?

A

pus-forming (massive amounts of neutrophils and other leukocytes are lysed by bacterial factors (e.g. leukocidin) and release their lysosomal contents in attempting phagocytic killing of the staphylococci).

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16
Q

What are the stages of an invasive pus-forming infection?

A
17
Q

What is a superantigen?

A

overrides the specificity of the T-cell response

18
Q

What are enterotoxins?

A

heat-stable toxins
- cause of gastrointestinal upset typical of food poisoning

19
Q

What causes food poisioning?

A

enterotoxins

20
Q

What is toxic shock syndrome toxin?

A

TSST: mass activation of T cells leads to large production of inflammatory cytokines (heat and protease-resistant TSST-1; chromosomal gene)

21
Q

What is exfoliative toxin?

A
  • (heat-stable, chromosomal)
  • B (heat-labile, plasmid) : SSSS
    (staphylococcal scalded-skin syndrome)
22
Q

What is toxic shock syndrome (TSS)?

A

Increased oxygenation of vagina by tampons, and foreign surface adhesion, caused massive growth

23
Q

What is staphylococcal scalded skin syndrome (SSSS)?

A

exfoliative toxins A, B cause loss of layers of the skin in SSSS -> Neutralizing Ab

24
Q

What bacteria causes surgery, implant, and instrument risk?

A

nosocomial staphylococci

25
Q

What bacteria has a dental extraction risk?

A

S. epidermidis

26
Q

What bacteria causes endocarditis?

A
  • acute: 60% S.aureus
  • if artificial heart valves: 80% S.epidermidis
27
Q

What are the percentages of most frequent causes of bacterial arthritis due to staphylococcus aureus?

A

Neonates: 10-25%
2 month to 2 years: 25-50%
3-10 years: 25-50%
Adults: 25-75%

28
Q

What is the epidemiology of staphyococcus aureus?

A
  • skin + mucosa + aerosols
  • surface survival: (hospital instruments, implants) and nosocomial (hospital-acquired)
  • high temperature (40ºC)
  • salt resistant
29
Q

What does coagulase do for other staphylococci like S. epidermidis and S. saprophyticus

A
  • Thick cell wall, slime capsule, (S.saprophyticus: urease secretion → acute cystitis)
  • Opportunistic hospital pathogens (instruments, catheters, heart valves)
30
Q

What bacteria are catalase, coagulase, clumping factor, protein A, leukocidin, staphylokinase, B-lactamase, and hemolysins virulence factors for?

A

staphylococci

Microbio Exam 2 (11 decks)

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