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PID Exams > Gram-Negative Bacterial Structure and Endotoxin in Human Diseases > Flashcards

Gram-Negative Bacterial Structure and Endotoxin in Human Diseases Flashcards

1
Q

Another name for group A strep is _

A

Streptococcus pyogenes

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2
Q

What is petechia? In the context of case 3, what is thought to cause it?

A

Petechia are small red spots (blood clots)

Endodoxin

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3
Q

What is the mechanism by which endotoxin causes its damage?

A

It causes clotting in the capillaries, causing adjacent tissues to die and blood to leak into the tissues

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4
Q

There are 6 microbes that cause meningitis. What are the 2 that cause meningitis in people of all ages?

A 
Streptococcus pneumoniae (all ages)
Neisseria meningitidis (all ages)
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5
Q

There are 6 microbes that cause meningitis. What is the one that causes it in individuals 3 months to 7 years, but is not uncommon due to vaccines? What is the target of the vaccine? What is the significance of 3 months?

A

Haemophilus influenzae type b
Vaccine targets the capsule of the microbe
3 months is usually when neonates run out of maternal antibodies, and the accompanying protection

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6
Q

There are 6 microbes that cause meningitis. What are the 3 major causes in neonates? Which 2 combine for 80% of cases?

A 
Streptococcus agalactiae (40%)
Escherichia coli (40%)
listeria monocytogenes
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7
Q

What is another name for group B strep?

A

Streptococcus agalactiae

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8
Q

In the context of case 3, what was the cause of the patient’s meningitis?

A

Neisseria menigiditis

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9
Q

In the context of case 3, what were the reasons (3) that neisseria meningiditis was thought to cause the patient’s disease?

A

– Extremely severe and rapidly progressing illness
– Purpura fulminans
– Cultures ultimately grew Neisseria meningitidis capsule group C

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10
Q

Another name for purpura fulminans is _

A

Waterhouse-Friderichsen Syndrome)

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11
Q

There are 5 major capsule groups of Neisseria meningiditis that the most common causes of meningitis. What are they? Which is not included in the vaccine and why?

A

A, B, C, Y and W135

B not included because its capsule is not immunogenic

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12
Q

What is the antibiotic treatment used to treat Neisseria meningiditis?

A

Cephalosporin (A beta lactam)

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13
Q

Neisseria meningiditis is gram positive or negative? Is it a rod, spirochete, coccus, diplococcous, or other? Encapsulated or not? What defining characteristic would it have under a microscope?

A

Gram negative
Diplococcus
Encapsulated
Kidney bean shaped cocci

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14
Q

In case 3, what was regarded as the ultimate cause of death?

A

Fulminant meningococcemia
Fulminant - rapid onset
meningococcemia - meningococci in the blood

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15
Q

Neisseria meningiditis has a capsule. What is its significance for the organism? How does it attach to the host?

A

Capsule in antiphagocytic, it doesn’t allow proper deposition of antibodies that lead to complement cascade
Neisseria meningiditis attaches by pili

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16
Q

In case 3, all the student were vaccinated for Neisseria meningiditis, including the meningitis group C capsule that infected the patient. Why was this ineffective? What is the new protocol now for a potential Neisseria meningiditis outbreak? Why is this better?

A

Because the production of IgM antibodies takes 4 days, too slow to help the patient.
Treatment of exposed people with Rifampin
Rifampin penetrates mucosal barriers very well

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17
Q

How is Neisseria meningiditis spread? Of the various capsule groups that cause disease, which is considered sporadic?

A

Intimate contact

Capsule B

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18
Q

True or false, in the brain, Neisseria meningiditis can lead to pus formation?
True or false, petechia and purpura fulminans are unrelated, and only purpura fulminans can lead to necrosis?

A

True

False - Petechia can become purpura fulminans, which can progress to necrosis if untreated

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19
Q

Gram positive cell walls are composed of _ and _. Which remains within the cell wall and which anchors to the PM below? What anchors to the outer membrane?

A

Lipotechoic acid - anchors
Techoic acid - within murein sac components
Gram + dont have outer membranes

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20
Q

How is the peptidoglycan layer similar and different between gram + and gram -?

A

Similar - same components

Different - Less cross linked

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21
Q

What are the 2 layers found outside the peptidoglycan layer of the gram - organism? Together, these form the _

A

Phospholipid layer
Lipopolysaccharide layer
Outer membrane of gram -

22
Q

What is the periplasm? What types of products may be trapped within the periplasm? Where would the capsule be found in a gram negative organism?

A

The periplasm is what is between the 2 membranes
Large molecules (above 800 MW)
Outside the outer layer

23
Q

How is the periplasm related to toxicity in e. coli?

A

In ecoli, the toxins produced are bigger than 800 MW, therefore they are trapped there until cell division, when they are released

24
Q

What are the 2 components of the periplasmic space in the gram negative bacteria?

A

Lipoprotein and think peptidoglycan wall

25
Q

What are 2 other names for endotoxin? What is its significance? What antibodies can protect against endotoxin?

A

Endotoxin AKA LPS AKA O-antigen
It is the immunogenic component of gram negative bacteria
Antibodies are not protective against LPS

26
Q

What are the 2 examples of outer membrane proteins of gram negative bacteria provided? What are their functions?

A

Porins - Trimers that transport molecules

Secretion systems - Transport virulence factors

27
Q

How are outer membrane proteins held in the outer membrane (2)?

A

Either embedded in the membrane or …

Covalently linked to peptidoglycan

28
Q

What are the 2 functions of pili in gram negative bacteria?

A

Attachment to host

Attachment to related bacteria

29
Q

What happens when you treat a gram negative bacteria with EDTA and lysozyme? Can this event be reversed?

A

You create a spheroplast - A cell wall deficient bacteria

If the whole cell wall is not removed, the cell wall can regenerate

30
Q

What are the 3 components of LPS?

A

O side chain sugars
Core polysaccharide
Lipid A

31
Q

What is the function of the O side chain in LPS? Is it immunogenic? Is it toxic?

A

It gives antigentic specificity

Immunogenic but not toxic

32
Q

What is the significance of the core polysaccharide? What are 2 examples of unusual sugars contained within?

A

Shared by all Enterobacteriaceae

Heptose and KDO (ketodeoxyoctonate)

33
Q

What is the significance of lipid A? What is the main chemical component? What is the major type of bond linking these components?

A

It is the toxic part of the LPS
N acetyl glucosamine
Phosphodiester bonds

34
Q

What is the significance of the phosphodiester bond in LPS? What is monophosphoryl Lipid A?

A

It is what confers toxicity

Mono-Lipid A is not toxic but it is immunogenic

35
Q

If you find ketodeoxyoctonate (KDO) anywhere, what does that tell you? What are the major components of all gram negative core proteins?

A

It tells you that the area has been contaminated by gram negative bacteria
KDO and heptose

36
Q

What is the difference between bacteremia and septicemia?

A

Bacteremia - bacteria in blood, no symptoms

Septicemia - bacteria in blood, with symptoms (e.g fever and hypotension) despite fluid resusitation

37
Q

True or false, only gram negative bacteria can cause septic shock.

A

False - both gram pos and neg can, but gram neg is better

38
Q

What is the main cause of multiorgan dysfunction syndrome?

A

The host’s immune system

39
Q

LPS and LOS differ because of _. An example of an organism with LOS is _. Which is more toxic?

A

Incomplete O side chain in LPS
Neisseria has LOS
Both just as toxic

40
Q

What is the difference between endotoxin and exotoxin?

A

Endotoxin - Part of gram negative cell wall

Exotoxin - Any secreted toxin from gram negative or gram positive

41
Q

How does exotoxin secretion differ in gram positive an negative organisms?

A

Secreted out into surroundings in gram positive, or into periplasm and or surrounding in gram negative

42
Q

Which is more lethal, exotoxin or endotoxin?

A

Exotoxin (lethal in ng to pg range)

Endotoxin (lethal in microgram range)

43
Q

Which is more likely to be enzymatic, exotoxin or endotoxin?

A

Endotoxin is non-enzymatic whereas many exotoxins are

enzymatic

44
Q

Which is more likely to be a genetic trait, exotoxin or endotoxin?

A

Exotoxin can be acquired

Endotoxin is a component of viable gram negative bacteria

45
Q

What is an enterotoxin?

A

An exotoxin that acts in the GI tract

46
Q

How will a gram negative cause shock? About how much toxin needed? How will a gram positive cause chock? About how much toxin needed? What about super antigen

A 
Gram neg., LPS about 1 microgram per human 
Gram positive, LTA / peptidoglycan, about 1 millgram per human 
Super entigent (e,g, TSS, only 0.1 microgram per human needed)
47
Q

What are the 2 types of Toll Like receptors bound by LTA? What is the 1 type of TLR bound by LPS?

A

LTA - TLR 2 or 6

LPS - TLR 4

48
Q

Upon binding TLR 2/4/6, what are the cytokines that will cause fever? What are the cytokines that will cause hypotension?

A

Fever - IL-1beta, IL-6

Hypotension - TNF-alpha

49
Q

What is a specific symptom that is associated with infection by superantigen? What are the associated cytokines? What cytokine causes superantigen hypotension?

A

Rash
INF-gamma and IL2
TNF-beta

50
Q

What are the 2 types of cells that superantigen crosslinks to get its response? What are the binding targets?

A

Cross links APC (macrophage or CD4) with T-cells

Binds MHC II (alpha or beta chain) with the alpha AND beta chain of TCR

51
Q

What is the specific molecule on T cells that TSST-1 recognizes? How does this molecule’s expression change from basal to infected state?

A

Recognizes the V-beta2 molecule

Basal 10% of cells, infection, now on 70% of cells

52
Q

What are the 3 superantigens that were provided as examples?

A

TSST-1
Staph enterotoxin
Strep scarlet fever toxin

PID Exams (17 decks)

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