staphylococcus- Daniels Flashcards

1
Q

general overview of staphylococcus

A

Gram + cocci

  • Non-motile
  • Non-spore forming
  • Predominantly facultative anaerobes
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2
Q

Basic phenotype of staphylococcus pneumoniae

A

1) Gram positive cocci
2) positive catalase test
3) ability to grow in 7.5% NaCl

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3
Q

The coagulase test

A

A) add bacteria to rabbit plasma
B) Differentiates S. aureus and 6 other species

(S. aureus causes the highest burden of disease in people)

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4
Q

T/F- coagulase negative staph are of considerable concern for humans

A

FALSE- only coagulase positive staph pose a serious threat

CoNS= coagulase negative staph

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5
Q

infections caused by S. aureus

A

1) Integumentary and wounds
2) Bacteremia - internal infections
3) Aspiration pneumonia
4) UTI
5) Toxic shock syndrome
6) scalded skin syndrome

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6
Q

Encounter

A

-Live on and around people
- Skin, mucosal surfaces
- Usually behave commensally
(Opportunistic in right conditions)

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7
Q

Entry of staph

A

Damage to skin/follicles

  • Wounds
  • Burns
  • Insect bites

Damage to mucosal surface

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8
Q

multiplication/spread

A

Variable with

1) Bacterial inoculum (more is worse)
2) Host immunocompetence
3) Location of infection

Bacteremia + immune compromise = trouble

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9
Q

Populations at elevated risk for severe infections from staphylococcus

A
Young children/Elderly
Diabetics
Individuals on immunosuppressive therapy
HIV+
Dialysis patients
IV drug users
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10
Q

Factors that enhance the ability to colonize and invade

A

MSCRAMMs = Microbial Surface Components Recognizing Adhesive Matrix Molecules”

1) Fibronectin binding proteins (FnbpA and FnbpB)
2) Collagen binding protein (CNA)
3) Clumping factors bind fibrinogen

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11
Q

Clumping factors that bind fibrinogen are key in the pathogenesis of what?

A

bacterial endocarditis

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12
Q

Acute suppurative inflammation =

A

accumulation of pus

Pus = neutrophils (a.k.a Polymorphonuclear WBCs or “PMNs”)

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13
Q

the formation of Abscesses

A

1) WBCs :The first ones to show up
2) Phagocytosis of foreign invaders
3) release ROS- reactive oxygen species
4) Release signaling molecules to call more WBCs to the area (cytokines)

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14
Q

what is the effect of the Polysaccharide capsule

A

blocks phagocytosis

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15
Q

what does Protein A block?

A

blocks antibody function

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16
Q

Panton-Valentine Leukocidin

A

a potent cytotoxin. acts as beta-pore-forming toxin.

very effective against PMN’s (neutrophils)

17
Q

SSSS – Staphylcoccal Scalded Skin Syndrome

A

caused by release of exfoliative toxins A and B

toxins cause the outer layers of epidermis to separate

18
Q

what is TSST-1?

A

A) its a Superantigen
B) cause an unregulated inflammatory response by activating high #s of CD4+ T cells

C) Cross link T-cell receptor with the MHC-II surface molecule of antigen presenting cells

19
Q

what type of molecules cause toxic shock syndrome?

A

Cytokines

TSS= “cytokine storm”

20
Q

what effect does IL-1 have on the body?

A

fever

21
Q

what does a large amount of TNF-alpha and beta cause?

A

Hypotension, leaky capillaries

22
Q

what do IFN-gamma and IL-2 causes?

A

Rash

23
Q

Staphylococcal Food Poisoning

A

A) Toxin is pre-formed in contaminated food
B) Not an INFECTION –> INTOXICATION
C) Enterotoxins A,B,C,D,E
D) Superantigens, Cause intense peristalsis

HEAT STABLE TOXINS

24
Q

what category of drugs are effective against staph

A

beta-lactam’s –> break up peptidoglycan layer

25
Q

what are the 2 penicillin binding proteins?

A

Transpeptidases and transglycosylases

26
Q

β-lactam antimicrobial agents are inhibitory substrates for what?

A

Penicillin binding proteins

27
Q

what extra protein does MRSA contain?

A

PBP2a

28
Q

why is MRSA a serious concern?

A

normal beta-lactam drugs are not effective against it

29
Q

what drug is used to treat MRSA?

A

Vancomycin

30
Q

what is Vancomycin?

A

A glycopeptide class antimicrobial drug

31
Q

what are the colonization site for MRSA?

A

Axilla, groin and Nares