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Micro/Immuno Exam 2 > Lecture 8A - STAPHylococcus (Dr. Daniels) > Flashcards

Lecture 8A - STAPHylococcus (Dr. Daniels) Flashcards

1
Q

Desribe Staphylococcus

A 
Gram Positive
cocci
non-motile
non-spore forming
facultative anaerobes
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2
Q

Staphylococcus - gram +/-?

A

Gram Postitive

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3
Q

Staphylococcus - catalase +/-?

A

Catalase +

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4
Q

Which genuses are catalse -?

A

streptococci

enterococci

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5
Q

Can staphylococcus grow in salt?

A

Yes (7.5% NaCl)

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6
Q

Now that we know it’s staph from the catalase test, let’s do a COAGULASE TEST. It’s positive! So what?

A

Now we know that it is one of 7 species of staph. Most of these species are important in animals, but one is important in humans.

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7
Q

Which coagulase positive staphylococcus is important for humans?

A

S. aureus

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8
Q

What can S. aureus cause?

A 
skin infections
bacteriemia
aspiration pneumonia
UTI
toxic shock syndrome
scalded skin syndrome
food poisoning
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9
Q

How do we encounter S. aureus?

A

live on 30-40% of people
muco-cutaneous jxns
great at surviving
behave commensally usually

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10
Q

how does S. aureus enter?

A

damage to skin (wounds, burns, insect bites)

damage to mucosal surfaces

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11
Q

What are factors for multiplication/spread of S. aureus?

A

Bacterial inoculum (how many are present)
immunocompetence
location of infection

Bacteremia + immune compromise = trouble

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12
Q

Who is at elevated risk for severe infections?

A 
Children/Elderly
Diabetics
Immunosuppressed ppl
HIV+
dialysis patients
IV drug users
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13
Q

What are some causes of immunosuppression?

A 
Autoimmune diseases (Rheumatoid arthritis)
Cancer chemotherapy
long-term corticosteroids
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14
Q

What are virulence factors of S. aureus?

A
  1. Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs)
  2. Polysaccharide capsule (blocks phagocytosis)
  3. Protein A - blocks antibody function
  4. Pore-forming toxins (pop PMNs)
    • Panton-Valentine Leukocidin
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15
Q

Name some MSCRAMMs

A 
FnpbA & FnbpB
     -fibronectin binding proteins
Collagen-binding protein (CNA)
Clumping factors bind fibrinogen
    -important for clot formation
     -coagulase + test
     -endocarditis
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16
Q

How does S. aureus cause damage?

A

Acute suppurative inflammation (accumulation of pus (PMNs))

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17
Q

How do PMNs cause abscesses?

A

release reactive oxygen species (ROS)

release cytokines

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18
Q

What is a potent pre-forming toxin?

A

Panton-Valentine Leukocidin

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19
Q

Why is ROS negative for the host?

A

damages host tissue (sustained inflammation)

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20
Q

Which toxins cause SSSS (Staphylcoccal Scalded Skin Syndrome)?

A

Exfoliative Toxins A & B

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21
Q

What do exfoliative toxins A and B do?

A

they are proteases that degrade desmosomal proteins in the skin, causing the layers of the skin to separate.

22
Q

a 9 year old girl had an oral abscess that lead to achy joints and muscles, septic shock, and renal failure. Why?

A

Her abscess was infected with S. aureus producing TSST-1, a superantigen.
TOXIC SHOCK SYNDROME

23
Q

what does TSST-1 do?

A 
It is a superantigen.
Unregulated activation of CD4+ cells
Cytokine Storm
   -IL-1
    -TNF alpha and beta
    -IFN-gamma, IL-2
24
Q

What does IL-1 lead to?

25
Q

What do TNF alpha and beta do?

A

hypotension
capillary leakage
(septic shock importance)

26
Q

What do IFN-gamma and IL2 do?

27
Q

What are the 3 staphylococcal disease we talked about in class?

A

SSSS
TSS
Food poisoning

28
Q

What does SSSS stand for?

A

Staphylcoccal Scalded Skin Syndrome

29
Q

Is food poisoning an infection?

A

No, it is an INTOXICATION.

30
Q

What causes food poisoning?

A

s. aureus secretes ENTEROTOXINS

31
Q

what is the most common enterotoxin?

A

Enterotoxin A (but there is B, C, D, and E too)

32
Q

Are enterotoxins superantigens?

A

yes. They are heat stable, so even cooking food after it has been left out causes food poisoning.

33
Q

How to Beta-Lactam antimicrobial drugs target microbes?

A

they act as inhibitory substrates for PENICILLIN BINDING PROTEINS that link peptidoglycan together

34
Q

What does translgycoxylase do?

A

binds NAG-NAM

35
Q

What does transpeptidase do?

A

binds amino acids of peptidoglycan to NAG-NAM

36
Q

How do penicillin binding proteins interact with penicillin and other Beta-lactam antimicrobial drugs?

A

They bind to the drugs instead of their substrates that normally build peptidoglycan of cell walls

37
Q

What are penicillin binding proteins?

A

transglycoxylase and transpeptidase (peptidoglycan bulding enzymes)

38
Q

what are some Beta lactam antimicrobial agents?

A 
penicillins
semi-synthetic penicillins
cephalosporins
carbapenems
monobactams
39
Q

Most S. aureus are METHICILLIN SUSCEPTIBLE. (MSSA)

A

MSSA stands for Methicillin susceptible S. aureus.

40
Q

What does MRSA stand for?

A

Methicillin resistant S. aureus

41
Q

Why is MRSA different from MSSA?

A

it has PSP2a, which will not bind beta-lactam antimicrobials.

42
Q

Why is MRSA scary?

A

It is resistant to antimicrobial drugs, and it can frequently carry resistance genes to other drug classes

43
Q

What is used to treat MRSA?

A

vancomycin
IV injected
glycopeptide class of drug

44
Q

What is VRSA?

A

Vancomysin resistant S. aureus

45
Q

What is VISA?

A

vancomycin intermediate S. aureus

46
Q

What gene to VRSA and VISA have that make them resistant to Vancomysin?

A

VanA

transferred horizontally by Enterococcus faecium via conjugative tranposon

47
Q

How many people carry MRSA?

A

less than 1%

48
Q

How many healthcare professionals carry MRSA?

49
Q

How many people still carry MRSA 4 years after a diagnosed infection?

50
Q

Where does MRSA colonize?

A

Nares
Axilla
Groin

Micro/Immuno Exam 2 (8 decks)

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