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Micro and Immunology > Aerobic gram +ve cocci - staph > Flashcards

Aerobic gram +ve cocci - staph Flashcards

1
Q

What is a good growth media for staph?

A

Blood agar

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2
Q

What is the main staph species that is a human pathogen?

A

Staph aureus

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3
Q

What does aureus stand for?

A

Golden

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4
Q

Are all staph aureus species golden?

A

No, only certain strains

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5
Q

Are the majority of staph strains gold?

A

No

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6
Q

Why is agar so good?

A

Very different melting and freezing points.

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7
Q

What does staph mean?

A

Grape

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8
Q

How is staph aureus identified?

A

ID by colonial and gram stain morphology

Coagulate positive

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9
Q

Where does staph aureus inhabit?

A

Anterior part of nose, skin and throat

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10
Q

What are the cell wall virulence factors of staph aureus?

A

Protein A

Fibronectin-binding protein

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11
Q

What does protein A do?

A

Binds to the Fc portion of IgG and inhibits phagocytosis

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12
Q

What does fibronectin normally do?

A

Our bodies produce fibronectin to coat our mucosal surfaces - by coating our respiratory tract, we block out gram -ve rod binding sites

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13
Q

What does fibronectin do against gram positive bacteria?

A

It doesn’t block gram +ve binding (rather gram -ve rod binding)

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14
Q

What happens regarding fibronectin when someone gets sick? How can they get pneumonia?

A

Acute phase reaction producing elastase which cleaves fibronectin off our mucosa.
This opens up gram -ve binding sites and staph aureus will be there no matter what.
These are the causes of hospital acquired pneumonia

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15
Q

What other virulence factors does staph aureus have other than its cell wall virulence factors?

A

Membrane damaging exotoxins - alpha, beta, gamma, delta and leukocidin

superantigen exotoxins

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16
Q

Proteins pumped out of cells, specifically manufactured by bacteria to be virulence factors that are released into the environment.

A

exotoxin

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17
Q

Protein toxins that have an affinity for a relatively highly conserved region of the TCR, the MHC class II complex. They stimulate a massive T cell response with outpouring of T cell cytokines.

A

Superantigen exotoxins

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18
Q

What are some superantigen exotoxins from staph aureus?

A

Exfoliatin
Enterotoxins A, B, C, D, E, G
Toxic Shock syndrome toxin

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19
Q

What does exfoliatin cause?

A

staphylococcal scalded skin syndromes

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20
Q

What do the staph enterotoxins cause

A

staphylococcal food poisoning

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21
Q

Infection occurring after or on top of an earlier infection, especially following treatment with broad-spectrum antibiotics.

A

Superinfection (or more aptly named supra-infection)

22
Q

What are the 4 major diseases/syndromes that staphylococcus aureus can cause?

A
  1. Localized abscess
    2 .Sepsis and acute endocarditis
  2. Hospital-acquired and post-influenzal pneumonia
  3. Toxin-associated syndromes
23
Q

Localized collection of pus

A

abscess

24
Q

What is the mainstay of therapy for a skin or soft tissue abscess?

A

Incision and drainage

25
Q

Localized abscess in bone

A

osteomyelitis

26
Q

What is important with abscesses?

A

let the pus out

27
Q

infection of the heart lining, including valves

A

endocarditis

28
Q

Staph abscesses that occur where there is a hair follicle.

A

Folliculitis / furunculosis

29
Q

Where can you never get folliculitis?

A

palms of hands and soles of feet

30
Q

What are the four variants of expanded staph scalded skin syndromes?

A

ritters disease
classic scalded skin syndrome
staphylococcal “scarlet fever”
Bullous impetigo

31
Q

Ritters occurs in who?

A

Newborns

32
Q

What is ritters? Why do children get it?

A

Newborns don’t have antibodies and their kidneys are not fully developed. They cannot get rid of the toxin - tend to desquamate at a very deep level - often fatal;

33
Q

If a woman enters the ER in a coma state, what should be removed, if present?

A

Tampon

34
Q

How did a particular brand of tampon lead to toxic shock syndrome?

A

25% of woman have staph aureus growing in their vagina - only a subset can cause TSS
Usually anaerobic in the vagina - but if a tampon is added, so is oxygen
Blood from menstruation also provides nutrients
Divalent cations (Mg2+) inhibits toxin production, but this tampon was very good at binding magnesium
The tampon was also so absorbant that it dried out the vagina, causing microfissures, allowing the staph to enter the blood

35
Q

How is toxic shock syndrome treated?

A

Removal of the source of intoxication - drain abscesses or remove tampon
Aggressive IV fluid replenishment
IV immunoglobulin

36
Q

When are antibiotics used for toxic shock syndrome?

A

mainly serve to prevent recurrences

37
Q

Mobile plasmid that breaks up penicillin type antibiotics

A

B-lactamase carrying plasmid

38
Q

What does CAMRSA stand for?

A

community acquired methicillin resistant staph aureus

39
Q

What is the special virulence factor of CAMRSA?

A

Panton-Valentine Leukocidin

40
Q

What does VISA stand for?

A

Vancomycin intermedaite staph

41
Q

What is the general trend of antibiotic resistance for staph aureus?

A

Getting more and more resistant

42
Q

What is CAMRSA not related to?

A

Hospital acquired MRSA

43
Q

What does CAMRSA produce?

A

Produces soft tissue abscesses which tend to relapse.

May cause sepsis

44
Q

What is the difference in terms of virulence and resistance between hospital acquired and community acquired MRSA?

A

Hospital - more resistant, less virulent

Community - more virulent, less resistant

45
Q

What is one way in which staph aureus and staph epi can be differentiated biochemically?

A

Staph aureus is coagulase positive

Staph epidermidis is coagulase negative

46
Q

Where does staph epi usually live?

A

Commensal bacterium of the skin

47
Q

How does staph epidermidis most often cause opportunistic infections?

A

Can cause opportunistic infections if you have a foreign body inserted like an IV line or through prosthetic devices

48
Q

What is needed to treat staph epi infections?

A

Vancomycin since it is very antibiotic resistant

49
Q

What does saprophyte mean?

A

Grows on dead, organic matter

50
Q

What does staph saprophyticus mostly cause?

A

2nd most common cause of UTI in young women

51
Q

Staph saprophyticus is coagulase __________.

A

negative

52
Q

Describe staph saprophyticus in terms of antibiotic resistance.

A

antibiotic susceptible

Micro and Immunology (38 decks)

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