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Lindsey's D&D Unit 3 > Mechanisms of Antimicrobial Resistance > Flashcards

Mechanisms of Antimicrobial Resistance Flashcards

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1
Q

The enzymes that perform cross-linking of peptidoglycan are called _____.

A

penicillin binding proteins (PBPs)

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2
Q

How does S. aureus prevent target-drug interaction in vancomycin resistance?

A

free vancomycin is bound in the existing peptidoglycan cell wall

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3
Q

What are efflux pumps?

A

structures in bacterial cell membranes that eliminate certain substances, incl. abx

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4
Q

How do bacteria prevent target-drug interaction in vancomycin resistance?

A

free vancomycin is bound in the existing peptidoglycan cell wall

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5
Q

The peptidoglycan precursor ends in _____.

A

2 D-alanines

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5
Q

_____ are β-lactam antibiotics with the broadest spectrum of activity against most gram - rods.

A

Carbapenems

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5
Q

Name 2 broad ways bacteria can become resistant to vancomycin.

A
  1. modifying the target 2. preventing target-drug interaction
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6
Q

_____ are structures in bacterial cell membranes that eliminate certain substances, incl. abx.

A

Efflux pumps

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7
Q

What does PBP stand for?

A

penicillin-binding proteins

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7
Q

Which drug induces erm?

A

macrolides

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8
Q

ESBLs are mostly found in ____, exclusively in _____.

A

plasmids; gram - rods

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9
Q

What are β-lactamases?

A

enzymes that inactivate β-lactam Abx by splitting the amide bond

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9
Q

What is the tx for species that express ampC?

A

carbapenems

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9
Q

How does Enterococcus spp become vanc resistant?

A

it changes the 5 member peptide that hangs off MurNAc so vancomycin cant recognize it

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10
Q

If erm is constitutively expressed, the bacteria will be resistant to _____. If erm is inducably expressed, the bacteria will be resistant to _____.

A

macrolides and clindamycin; macrolides only

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11
Q

Carbapenemases causing the most problems are plasmid-mediated and are found mainly in some _____ isolates, although transfer to ____ has occurred.

A

Klebsiella pneumoniae; E. coli

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12
Q

Give an example of intrinsic resistance.

A

vancomycin resistance of gram- organisms b/c it can’t penetrate the outer membrane

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13
Q

Where are porins found?

A

in the outer membrane of gram - bacteria

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15
Q

What is intrinsic resistance?

A

occurs just because via natural properties of the bacteria

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16
Q

β-lactamases are found in both gram + and gram - bacteria, but the worse ones are in the _____.

A

gram -

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16
Q

What is KPC?

A

Klebsiella pneumoniae carbapenemase- hydrolyzes all carbapenems and all other β-lactams

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16
Q

____ targets DNA gyrase as well as Cipro but also targets topo IV.

A

Levofloxacin

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17
Q

Carbapenemases causing the most problems are ____ and are found mainly in some Klebsiella pneumoniae isolates, although transfer to E. coli has occurred.

A

plasmid-mediated

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18
Q

What is mecA?

A

gene staph has that encodes a different PBP- causes MRSA

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19
What does ESBL stand for?
extended spectrum beta-lactamases
20
Efflux pumps are found in _____ and _____ bacteria.
gram -, gram +
20
Anaerobic bacteria are inherently resistant to \_\_\_\_\_.
aminoglycosides
21
What do porins do?
form hydrophilic channels to allow selective uptake of nutrients, including some Abx
21
What is the D test?
distinguishes between erm and efflux-based resistance in bacteria; erm = D shape colony growth
22
\_\_\_\_ is much for effective for gram negative bacteria than gram positives.
Cipro
23
During peptidoglycan cross linking, a ____ is cleaved
D-alanine
23
PBPs perform _____ and/or _____ reactions.
transpeptidase; transglycosylase
24
How are mecA staph treated?
5th gen cephalosporin
25
Carbapenems are β-lactam antibiotics with the broadest spectrum of activity against most \_\_\_\_.
gram - rods
25
\_\_\_\_\_ causing the most problems are plasmid-mediated and are found mainly in some Klebsiella pneumoniae isolates, although transfer to E. coli has occurred.
Carbapenemases
26
What does ampC encode? Why is it unique?
a β-lactamse that can hydrolyze penicillins, cephalosporins, and is not inhibited by beta-lactamase inhibitors
28
Where is ampC found?
the chromosome of gram - rods (Enterobacter, Pseudomonas)
29
Cipro is much more effective against _____ bacteria than _____ ones.
gram negative; gram positive
30
Name 2 ways bacteria become resistant to macrolides.
1. methylate the 23s ribosome via erm gene 2. prevent drug-drug interaction via efflux pumps
32
\_\_\_\_\_\_ act by irreversibly binding and inactivating the transpeptidase reaction of PBPs, thereby inhibiting peptide cross-linking and peptidoglycan synthesis.
β-lactam antibiotics
33
Where are the β-lactamase genes located?
on chromosomes (Klebsiella pneumoniae) or on plasmids (Staph. aureus, E. coli, H. influenzae)
34
Where is the erm gene found?
on transposons or plasmids
36
Name 3 ways bacteria become resistant to β-lactam antibiotics.
1. modify the drug (enzymatic destruction) 2. modify the target (alter the PBPs) 3. prevent drug-target interaction (porins and efflux mechanisms)
37
\_\_\_\_\_ occurs just because, via natural properties of the bacteria.
Intrinsic resistance
38
ampC expression is either ____ or \_\_\_\_\_.
inducible, constitutive
39
β-lactam antibiotics act by irreversibly binding and inactivating the transpeptidase reaction of PBPs, thereby inhibiting ____ and \_\_\_\_\_.
peptide cross-linking; peptidoglycan synthesis
41
\_\_\_\_ is due to genetic mutations or acquisition of new genes (plasmids, bacteriophages, transposons).
Acquired resistance
42
What are the 3 major mechanisms of resistance?
1. inactivation/modification of the drug 2. altered antibacterial target 3. reduced drug delivery to the target
43
\_\_\_\_\_\_ is formed by the addition of subunits called precursors (GlcNAc-MurNAc with 5 aas on the MurNAc).
Peptidoglycan
44
\_\_\_\_ targets topo IV preferentially; it's best against gram positives but still has some gram negative activity, but NOT against Pseudomonas.
Moxifloxacin
45
How do bacteria modify the target in vancomycin resistance?
change the 5 member peptide that hangs off MurNAc so vancomycin cant recognize it
45
\_\_\_\_\_ has good gram negative activity and much improved gram positive activity.
Levofloxacin
47
Peptidoglycan is formed by the addition of subunits called precursors (\_\_\_\_\_ with 5 aas on the \_\_\_\_\_).
GlcNAc-MurNAc; MurNAc
48
How do macrolides work?
bind to the 23s portion of the 50s ribosome to inhibit peptide chain elongation
49
What do narrow spectrum β-lactamases do?
hydrolize penicillin-type Abx
49
What do the vanA and vanB genes in VRE do?
change the peptide chain from D-ala, D-ala to D-ala, D-lactate
51
β-lactam antibiotics act by irreversibly binding and inactivating the _____ reaction of PBPs, thereby inhibiting peptide cross-linking and peptidoglycan synthesis.
transpeptidase
52
Cipro preferentially targets ____ over \_\_\_\_.
DNA gyrase; topo IV
53
What genes do VRE have that encode their vanc resistance? Where are they located?
vanA and van B; plasmids
54
\_\_\_\_ perform transpeptidase and/or transglycosylase reactions.
PBPs
55
Which bacteria changes the 5 member peptide that hangs off MurNAc so vancomycin cant recognize it?
enterococcus (VRE)
57
Which bugs have mosaic PBPs?
Strep. pneumonia and N. gonorrhoeae
59
Where is NDM-1 found?
on plasmids
60
What is acquired resistance?
genetic mutation or acquisition of new genes (plasmids, bacteriophages, transposons)
61
Changes in porins or efflux pumps may cause \_\_\_\_.
changed uptake of Abx
62
Where is KPC found?
on plasmids
62
Levofloxacin targets DNA gyrase as well as Cipro but also targets \_\_\_\_.
topo IV
63
How can bacteria become resistant to fluoroquinolones?
change amino acids in DNA gyrase and topo; drug efflux
64
Moxifloxacin targets _____ preferentially; it's best against gram positives but still has some gram negative activity, but NOT against Pseudomonas.
topo IV
64
\_\_\_\_\_ are inherently resistant to aminoglycosides.
Anaerobic bacteria
65
DNA gyrase is targeted by quinolones in _____ bacteria; topo IV is targeted by them in \_\_\_\_\_.
gram (-); gram (+)
66
Methylation of the ribosome confers resistance to ____ and ____ Abx.
macrolides; clindamycin
68
Carbapenems are _____ with the broadest spectrum of activity against most gram - rods.
β-lactam antibiotics
71
Extended spectrum beta-lactamases (ESBLs) are notable bc they can attack most \_\_\_.
cephalosporins
72
What is NDM-1?
enzyme that hydrolyzes all β-lactams except aztreonam
73
Levofloxacin has good ____ activity and much improved _____ activity.
gram negative; gram positive
74
What does a carbapenem treat?
gram - rods
75
\_\_\_\_\_ preferentially targets DNA gyrase over topo IV.
Cipro
76
How are mosaic PBPs formed?
by picking up naked DNA from the environment and swapping them for similar pieces of their own PBP DNA
77
Peptidoglycan is formed by the addition of subunits called _____ (GlcNAc-MurNAc with 5 aas on the MurNAc).
precursors
78
What are penicillin binding proteins (PBPs)?
enzymes that cross-link peptidoglycan
80
Which bacteria binds free vancomycin up in the cell wall, preventing its action?
S. aureus
81
Moxifloxacin targets topo IV preferentially; it's best against _____ but still has some _____ activity, but NOT against \_\_\_\_\_\_.
gram positives; gram negative; Pseudomonas
82
Where are the amino acids changed on DNA gyrase and topo IV to create fluoroquinolone resistance?
quinolone-resistance-determining-region (QRDR)
84
What do quinolones target in gram - bacteria? gram + ones?
DNA gyrase; topo IV
85
How are aminoglycosides modified?
N-acetylation, O-nucleotidylation, O-phosphorylation
86
How do you treat bugs that carry ampC?
remember which ones they are ((Enterobacter, Pseudomonas- gram (-) rods)) and give a carbapenem
87
What does KPC stand for?
Klebsiella pneumoniae carbapenemase
89
How are the vanc resistant strains of S. aureus different?
1. thickened peptidoglycan 2. less cross-linking
90
Which abx binds to the 23s portion of the 50s ribosome to inhibit peptide chain elongation?
the macrolides
91
What are the side effects to aminoglycosides?
ototox and renal tox

Lindsey's D&D Unit 3 (12 decks)

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