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Immunology Pt. 2 > Staphylococcus > Flashcards

Staphylococcus Flashcards

1
Q

Staphylococcus (Characteristics)

A
  • Gram positive, cocci, non motile
  • Pairs; short chains; clusters
  • Facultative anaerobes; diversity
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2
Q

Staphyle:
Coccus:

A

Staphyle: bunch of grapes
Coccus: a grain or berry

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3
Q

Indigenous Bacteria

A

Establish residence on surface tissue or alimentary tract; especially the anterior nares

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4
Q

Staphylococci are part of the ______ ______

A

Natural flora

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5
Q

There are >__ species of Staphylococcus

A

20

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6
Q

Coagulase

A

A biochemical test that differentiates S. aureus from other Staph - contributes to the clotting of plasma

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7
Q

Coagulase converts ______ to ______

A

Fibrinogen to Fibrin

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8
Q

How do we differentiate Staphylococcus and Streptococcus (both gram positive)

A

Catalase produced by staphylococcus under aerobic conditions

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9
Q

Multiple _______ ______ assist establishing a staphylococcus infection

A

extracellular factors

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10
Q

Protein A

A

Unique to S. Aureus

- Major protein component of cell wall that is covalently bound to peptidoglycan

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11
Q

IgG effects on Protein A

A
  • With IgG molecules bound in the “wrong” orientation (om relation to normal antibody function), the IgG disrupts opsonization and phagocytosis of bacteria
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12
Q

Toxins produced by S. aureus (4)

A

1) Hemolysins
2) Leukotoxins
3) Enterotoxins (superantigens) - toxic shock syndrome
4) Exfoliative toxins

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13
Q

Hemolysins

A

Red blood cell membrane damaging proteins

- Contribute to pathogenicity by producing tissue damage after the establishment of a focus infection

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14
Q

Leukotoxin

A

A two protein toxin, attacks polymorphonuclear leukocytes and macrophage

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15
Q

Enterotoxins

A

Large family of Staphylococcus toxins, superantigens

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16
Q

Enterotoxins
Function:
Source:
Symptoms:

A

Function: Cause diarrhea and emesis
Source: S. aureus contaminated foods
Symptoms: Within 2-6 hours of ingestion
- Cramping, nausea, vomiting, diarrhea

17
Q

Enterotoxins are _____-stable

A

heat

18
Q

TSST

A

Toxic shock syndrome toxin

19
Q

Enterotoxins and TSST bind directly to ______ and ______ independent of antigen

A

MHC class II; TCR

20
Q

Enterotoxins and TSST: method of toxicity

A

Massive cytokine production yields systemic toxicity of host/ Suppression of the adaptive immune response

21
Q

Exfoliative toxin

A

2 forms ETA/ETB - proteases

Stimulate lysis of the intercellular attachment between cells of the epidermis

22
Q

Staphylococcus Epidemiology

A

Staphylococcus are a normal component of human indigenous flora and are carried asymptomatically at several body sites, especially anterior nares

23
Q

Staphylococcus Transmission

A

Direct contact by the hands is the most important route of transmission

24
Q

Staphylococcus Infection

A
  • Typically localized
  • Intact skin major barrier to infection
  • Skin primary sites of infection
25
Q

Appearances of Staphylococcus infectio``````n

A 
Folliculitis
Boil
Impetigo
Scalded skin syndrome
Pneumonia
26
Q

Treatment of S. Aureus infections

A
  • Adequate drainage of wound
  • Removal of foreign objects
  • Antibiotic Therapy
    • Methicillin
    • Vancomycin
27
Q

Methicillin Resistant S. Aureus (MRSA)

A

MR of SA is due to the selection of SA with mutations within the Penicillin Binding Proteins that have low affinity for penicillin

28
Q

PBP

A

Penicillin Binding Proteins

29
Q

Vancomycin Resistance

A
  • SA strain resistant to intermediate, but clinically significant levels of vancomycin VIrSA
  • Typically in MRSA - patients with prolonged vancomycin therapy, up to 18 wks, selects for VIrSA
  • VIrSA resistance due to changes in cell wall
30
Q

MICs for Vancomycin

A

SA vancomycin - susceptible: 0.5 - 2µg/ml
SA vancomycin - intermediate (VIrSA): 4-8 µg/ml
SA vancomycin - resistant (VRSA): >16 µg/ml

31
Q

HA-MRSA vs. CA-MRSA

A

HA-MRSA infection is easily contracted in hospital settings

CA-MRSA infection spreads through those living in close contact, such as military barracks, dormitories and gyms

32
Q

S. Epidermis

A

Low virulence

  • Hospital acquired - contamination of surgical site binds to plastics
  • Treatment, problem multi-drug resistant use antibiogram
33
Q

S. Saprophyticus

A

Urinary tract infections selectively binds to cells of the urinary tract
- Does not posses any virulence factors found in SA

Immunology Pt. 2 (11 decks)

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