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Infectious Disease Final > Lecture 8 - STAPHYLOCOCCUS > Flashcards

Lecture 8 - STAPHYLOCOCCUS Flashcards

1
Q

are staphylococci gram (+) or gram (-)?

A

gram (+)

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2
Q

are staphylococci catalase (+) or (-)

A

catalase (+)

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3
Q

what does catalase do?

A

breaks down hydrogen peroxide into water and oxygen (also breaks down other superoxide products of respiratory burst).

inactivates the reactive species that the immune system produces to destroy in it order for the staphylococci to protect itself

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4
Q

is staphylococci aerobic or anaerobic?

A

aerobic (facultative), meaning that it is aerobic but CAN survive in an anaerobic environment

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5
Q

how does staphylococci grow?
does it have flagella?

A

staphylococci grows in CLUSTERS and does NOT have flagella

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6
Q

does staphylococci form spores? explain

A

NO, but it can still survive in harsh conditions

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7
Q

what type of harsh conditions can staphylococci survive in?

A

HIGH SALT and WIDE TEMPERATURE RANGE

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8
Q

is staphylococci part of our endogenous flora or is it always pathogenic?

A

it’s part of our endogenous flora on skin and mucosal surfaces.

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9
Q

how is staphylococci transmitted?

A

through direct contact or exposure to fomites

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10
Q

what is a fomite?

A

an inanimate object that can transfer infection

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11
Q

is staphylococci dangerous?

A

it’s part of our endogenous flora so usually not.
even if we are infected, immune system can handle most of the time

BUT if it does infect us and the immune system is overwhelmed it causes tissue damage and quickly becomes systemic and deadly. it can get into the blood stream

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12
Q

give an example of a specific staphylococci species

A

staphylococcus aureus

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13
Q

what is unique about staphylococcus aureus bacteria?

A

it produces important enzymes (coagulase), toxins (alpha-toxin), and superantigens (SAgs)

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14
Q

where does staphylococcus aureus habitate?

A

in the nostrils and perineum

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15
Q

what infections does staphylococcus aureus cause?

A

DEEP INFECTIONS – pneumonia, osteomyelitis, abcesess, TSS (toxic shock syndrome)

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16
Q

does staphylococcus aureus cause:

-biofilm?
-boils?
-UTI?

A

creates biofilm and boils but NOT UTI

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17
Q

Staphylococcus aureus production of superantigen correlates with……

A

SEVERE DISEASE

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18
Q

If staphylococcus colonizes in the vaginal area, what happens?

A

TOXIC SHOCK SYNDROME

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19
Q

Does staphylococcus aureus cause abcesses?

A

YES.
these can aid in the spreading. spread through direct contact

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20
Q

staphylococci primarily replicates where?

A

in nasopharynx – very moist there (mucosal membranes)

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21
Q

why is staphylococcus so prominent in hospitals?

A

they can easily colonize medical devices.
also, spread through direct contact

22
Q

what is responsible for TSS?

A

production of superantigens by staph aureus

23
Q

how many different serotypes are there of staphylococcus aureus?

A

11 serotypes

24
Q

what are the structural components of staphylococcus aureus that are classic for a gram positive bacteria?

what are the surface proteins on staphylococcus aureus that are relatively unique?

A

classic to gram(+): highly cross linked peptidoglycan and teichoic acid

UNIQUE: SpA (surface protein A) and Clf (clumping factor)

25
Q

what is the function of teichoic acid?

A

spans the peptidoglycan layer to give rigidity

26
Q

what is the function of surface protein A?

A

binds the Fc region of antibodies (immunoglobulins)

27
Q

what is the function of Clf?

A

clumping factor.

binds fibrinogen and FnBP (Fibronectin-binding proteins) together

–fibrinogen is crucial to the host cell function. thus, Clf aids in bacterial function by binding to these. fibrinogen acts as a host attachment protein for the bacteria

28
Q

name the layers of staphylococcus aureus

A

has a capsule layer and a polysaccharide slime layer, also peptidoglycan layer that is crosslinked by teichoic acid

29
Q

name 4 enzymes produced by staphylococcus aureus and state their function

A

-coagulase – converts fibrinogen to fibrin which creates a physical barrier between the bacteria and the immune cells trying to destroy it

-hyaluronidase – breaks down hyaluronic acid present on host cell membrane

-lipases – hydrolyzes lipids to help break down host cell membrane

-Nucleases – digests the DNA of host cell to destroy the cell completely

30
Q

the cytotoxins produced by staphylococcus aureas are cytolytic for which 3 cells?

A

erythrocytes (RBC)
keratinocytes
fibroblasts

31
Q

name the cytotoxins produced by staph aureus

A

alpha, beta, delta, gamma, and PVL (panton-valentine leukocidin)

32
Q

name the functions of alpha toxin and PVL (panton-valentine leukocidin) produced by staph aureus

A

alpha toxin — pore forming cytotoxin NOT EFFECTIVE AGAINST NEUTROPHILS

PVL – targets neutrophils (since alpha toxin cant) and platelets

33
Q

name all of the toxins produced by staphylococcus aureus

A
  1. cytotoxins (alpha, beta, delta, gamma, PVL)
  2. Exfoliatin
  3. SUPERANTIGENS (enterotoxins)
34
Q

what is the function of exfoliatin toxin

A

a protease that disrupts the stratum granulosum (layer of the skin) that prepares the skin for a productive infection

35
Q

go into more detail about staph aureus superantigens

A

the enterotoxins (A-V) are superantigens. there are over 20 of them produced by staph aureus. they cause food poisoning

ex: SEA (Staph enterotoxin A_, SEB, SEC, etc

other superantigen toxins produced by staph aureus produce TSS (toxic shock syndrome) due to a massive cytokine release. causes leaking and destruction of endothelial cells

36
Q

explain how staph aureus works to cause cell death

A

FNBP binds to fibrinogen sheath on the host cell membrane.
staph A secretes alpha cytotoxin which is a PORIN. as more and more pores devleop the cell begins to be destroyed. (the bacteria can move through a porin between cells and infect many adjacent cells by moving through the porins produced by alpha toxin) COAGULASE forms a fibrin wall from fibrinogen that prevents the neutrophils from attacking the staph Aureus that is now invading the cell

staph A gets into bloodstream through the destroyed epithelial cells and causes major tissue damage and infection

37
Q

name 3 toxin-mediated diseases from staphylococcus aureus

A

-scalded skin syndrome (due to exfoliatin)
-food poisoning (through ingestion of superantigen enteroxin)
-toxic shock syndrome (through toxic shock syndrome toxin-1)

38
Q

what does pyogenic mean?

A

causes fever

39
Q

what cutaneous infections does staph A cause?

A

causes pyogenic, pus-forming abcesses

impetigo
folliculitis
farbuncles (BOILS)
cabuncles (MULTIPLE boils)
wound infections

40
Q

why is staph aureus commonly associated with wound infections?

A

easy entry for it go get in
spread via direct contact

41
Q

if staph a gets into the blood, what dangerous conditions can it cause?

A

can spread anywhere and cause:

-endocarditis
-pneumonia
-septic arthritis at large joints

42
Q

how does septic arthritis occur?

A

the antigen-antibody complex is insoluble and depositis in joints.

RESULT OF OUR OWN IMMUNE RESPONSE

43
Q

Does staph A have pathogenicity islands?

A

yes – extrachromosomal.
how the virulence genes are controlled

44
Q

boils are _____ infections

A

cutaneous (skiN)

45
Q

explain how boils develop in a staphylococcus aureus infection

A

staph A can get into the skin through a hair follicle via direct contact with the bacteria.

the bacteria can spread to the subcutaneous tissue and white blood cells are continually recruited to help fight the infection. this buildup creates an abcess and is plugged by necrotic material (dead white blood cells)

46
Q

where does staphylococcus aureus shed?

A

nasal

47
Q

explain how TSS develops due to staphylococcus aureus

A

staph A is normally commensal in the vaginal area. there is normally a free flow of fluids.

however, when a tampon is inserted the free flow of fluids is blocked which propagates the replication of staphylococcus aureus. superantigen is expressed producing a cytokine storm activating a large number of T cells anf generating an overwhelming immune response

48
Q

is staphylococcal resistant to antibiotics?
explain

A

has 2 means of antibiotic resistance

has penicillinase to open the beta lactam ring of penicillin to break down any penicillin antibiotic

the target of penicillin is a non-self (altered) petidoglycan transpeptidase. staph aureus contains a gene on its pathogenicity island that expresses an altered PBP (called penicillin binding protein 2 – PBP2) that penicillin cannot recognize

49
Q

WHY is peptidoglycan transpeptidases the target of penicillin?

A

if penicillin inhibits this enzyme, the bacteria cannot produce their protective cell wall

50
Q

as mentioned, staphylococci aureus has 2 major ways of resisting penicillin antibiotics.

what other antibiotic is it capable of resisting which poses a major concern?

A

there are some vancomycin-resistant staph aureus strains which is a MAJOR concern since vancomycin is a last resort antibiotic.

51
Q

what does MRSA stand for and mean

A

methylcillin resistant staphylococcus aureus

staph aureus that is resistant to penicillin

52
Q
A

Infectious Disease Final (13 decks)

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