4 lecture peptidoglycan synthesis and antibiotics Flashcards

1
Q

what blood pressure is considered to be hypotensive?

A

Any systolic blood pressure below 90/x is considered hypotension.

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2
Q

what is macular erythroderma?

A

a skin condition characterized by flat reddened skin.

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3
Q

what is the number one thing you do for a septic patient to control their blood pressure?

A

give them fluids and electrolytes.

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4
Q

If you take cultures and find out that the bacteria you are dealing with is MRSA, what antibiotic do you quickly give?

A

1) vancomycin

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5
Q

What does CA-MRSA mean? What toxin does it release?

A

1) Community associated Methacillin resistant S. Aureous.2) The toxin it releases is enterotoxin C

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6
Q

Why would you ever give IVIG’s?

A

During sepsis with excess superantigen release. IG’s bind up the Toxin.

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7
Q

The peptidoglycan wall is bound by which two types of covalent bonds?

A

1) glycosidic2) peptide

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8
Q

what happens to bacteria that do not have an intact cells wall?

A

they lyse due to turgor pressure

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9
Q

When does peptidoglycan synthesis/hydrolysis occur in normal bacterial cultures?

A

during cell division

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10
Q

T/F Peptidoglycan is unique to bacteria?

A

True. (many antibiotic targets)

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11
Q

Where is the gram - peptidoglycan layer located?

A

within the periplasm

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12
Q

what percentage of gram + peptidoglycan is cross linked? Gram -?

A

1) 75%2) 25%

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13
Q

what is the reason for the decreased cross linking in gram - bacteria compared to gram +?

A

It is because the peptidoglycan of a gram - bacteria is partially covalently bound to lipoproteins.

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14
Q

what kind of covalent bond binds NAG to NAM?

A

Beta 1-4 glycosidic bond

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15
Q

how do you make NAM?

A

NAG + lacteal group

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16
Q

what group carries the tetrapeptide with alternating L and D amino acids?

A

The NAM is the polysaccharides that carries the four amino acids. Therefore, it is the where the cross linking is occuring. NAM to NAM

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17
Q

What makes the peptide cross link that connects the 4th amino acid of one NAM to the 3rd amino acid of another NAM?

A

5 glycine residues

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18
Q

To make NAG into Nam, where does the lacteal group have to be attached?

A

The lacteal group attaches to the C3 carbon

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19
Q

T/F Only MA carries the tetrapeptide chains?

A

True. Recall that MA=NAM

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20
Q

What is so significant about the D amino acids in the bacterial cell wall?

A

The body cannot breakdown/process D amino acids and they are only found in bacteria.

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21
Q

Which amino acids make up the tetrapeptide link?

A

1) L-alanine2)D-Glutamate3)L-lysine or diaminopimelic acid4)D-alanine

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22
Q

Penicillin and cephalosporin do what?

A

They block the enzymes that form the crosslink between the 3rd and 4th amino acid that is connected to NAM. This disrupts the formation of peptidoglycan.

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23
Q

Where does Vancomyocin function?

A

Vancomyocin binds to the 5 amino acid chain of NAM and prevents the transpeptidase reaction. This prevents the cross linking.

24
Q

What are PBP’s?

A

Penicillin binding proteins

25
Q

how many PBP’s does E.coli have? S. Aureus?

A

E. Coli= 6S. Aureus=4

26
Q

where does synthesis of peptidoglycan begin?

A

in the cytoplasm

27
Q

fructose-6-phosphate is the sugar base for which compound in peptidoglycan synthesis?

A

UDP-NAG

28
Q

PEP enzyme helps with the conversion of NAG to NAM. What is the antibiotic that inhibits this enzyme by acting as an analog?

A

phosphonomycin

29
Q

what is the name of the carrier lipid that carriers UDP-NAM to the outer peptidoglycan structure?

A

Undecaprenol phosphate (AKA Bactoprenol)

30
Q

what does bacitracin do to stop bacterial cell wall synthesis?

A

it inhibits the regeneration of BP from BPP. Recall this is the carrying lipid.

31
Q

How is cross linking of the peptidoglycan wall carried out?

A

Through transpeptidation. It does it through displacing the terminal D-alanine.

32
Q

How do all beta lactam antibiotics work?

A

They prevent transpeptidation of the peptidoglycan.

33
Q

what does lysozyme do to bacteria?

A

it hydrolyses the glycosidic linkages of peptidoglycan.

34
Q

Name 3 specific bacteria that you would not use antibiotics to destroy the peptidoglycan wall?

A

1) mycoplasma (no cell wall)2) mycobacterium (very thick/tough cell wall)3) chlamydia

35
Q

How does the antibiotic cycloserine work?

A

It prevents the formation of UDP-NAM(aa5) form UDP-NAM(aa3). So it prevents the addition of the last two D-alanines

36
Q

T/F Group A strep are 10X more sensitive to bacitracin than most other bacteria?

A

Yes. This helps to differentiate Group A strep.

37
Q

What characteristics define Group A strep?

A

Gram + coccichainsCatalase NegativeBacitracin sensitive

38
Q

T/F Bacitracin should be taken orally when you have a known enteric Group A strep infection?

A

False.Bacitracin is topical only. Ingestion is toxic.

39
Q

Augmentin is made from 2 drugs which are?

A

1)Amoxicillin2) Clavulanic acid

40
Q

what is the defining chemistry of a bata lactam antibiotic?

A

a four sided ring with one Nitrogen and 3 carbons.

41
Q

Some beta lactams have a sulfer atom attached which can induce what in the body?

A

Type 1 hypersensitivity reactions.

42
Q

What do beta lactam antibiotic bind to?

A

they bind to the penicillin binding proteins (PBP)

43
Q

T/F PBP’s are associated with transpeptidation reactions?

A

True. Recall this is the target of Beta lactams.

44
Q

What leads to beta lactam resistance such as penicillin resistance?

A

If the bacteria replaces the normal PBP with PBP2a you get antibiotic resistance to the beta lactams.

45
Q

T/F penicillins normally target gram + bacteria?

A

True. However, there are some that can extent to hit gram (-) as well.

46
Q

T/F Augmentin is considered a broad spectrum antibiotic?

A

true

47
Q

T/F Penicillin is considered a narrow spectrum antibiotic?

A

True

48
Q

Where did Beta lactams come from?

A

molds originally

49
Q

T/F Carbapenems and penems are the most narrow type of beta lactam antibiotics?

A

False. They are the most broad and is why they are frequently used.

50
Q

T/F you would give cephalosporin to help kill MRSA?

A

False. MRSA is resistant so you would have to use vancomycin.

51
Q

T/F Monobactums contain a nucleus and a beta lactam ring?

A

true. They are a single (mono) lactam ring structure with no other fused rings.

52
Q

What is the purpose of a Beta lactamase inhibitor?

A

They minimally help stop the breakdown of Beta lactams allowing the antibiotic effects to work better. Released from bacteria.

53
Q

What toxin does CA-MRSA strain USA400 make?

A

Enterotoxin C

54
Q

What decreases the cross linking of peptidoglycan in gram neg. bacteria?

A

Being covalently bound to lipoproteins

55
Q

Streptococcus pyogenis falls into which group?

A

Group A strep

56
Q

What is the most commonly used beta lactamase inhibitor?

A

Clavulanic acid