Lecture 13: Antibiotics Part 2 Flashcards

1
Q

What is intrinsic resistance vs. acquired resistance?

A
  1. Intrinsic = bacteria are normally resistant to an antibiotic without any changes in their genetic composition
  2. Acquired = bacteria gain resistance through mutations or through mobile genetic elements (plasmids)
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2
Q

What are some mechansisms of antibiotic resistance in bacteria?

A
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3
Q

What is driving the emergence of antibiotic resistance?

A
  1. Healthcare: overprescription of antibiotics
  2. Agriculture: giving animals antibiotics
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4
Q

It is estimated that antibiotic resistance can become widespread in how long after the introduction of a new antibiotic?

A

2-3 years

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5
Q

What is the reservoir of mobile antibiotic resistant genes?

A

Natural environment, especially soil

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6
Q

What percent of antibiotic prescriptions are not needed?

A

Estimated 28%

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7
Q

What are some medically important organisms (Gram-negative and Gram-positive)?

A
  1. Gram-negatives
    - Extended-spectrum β-lactamase (ESBL) GN
    - Carbapenem-resistant (CR) GN
  2. Gram-positives
    - Methicillin-resistant Staphylococcus aureus (MRSA)
    - Vancomycin-resistance Enterococcus faecium/faecalis (VRE)
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8
Q

What are the β-lactamase classifications?

A
  • Serine β-lactamases (contain serine at their active site)
  • Metallo-β-lactamases (contain zinc at their active site)
  • Ambler classification (stuctural homology)
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9
Q

What is the last resort for β-lactam resistant organisms?

A

Polymixins

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10
Q

What are the β-lactamase genes called?

A

bla

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11
Q

What antibiotics do ESBLs hydrolyze? When are these effective?

A
  • 1st-3rd gen cephalosporins
  • Penicillins
  • Monobactam
  • Effective when combined with clavulanic acid (inhibitor)
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12
Q

What organisms are ESBL producers?

A
  • Klebsiella pneumoniae
  • K. oxytoca
  • Escherichia coli
  • Proteus mirabilis
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13
Q

What are the most common ESBLs (extended-spectrum B-lactamases)?

A

The CTX-M enzymes which emerged in the 1990s

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14
Q

What antibiotics do carbapenemases hydrolyze?

A
  • Penicillins
  • Cephalosporins
  • Monobactams
  • Carbapenems
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15
Q

What is the most common carbapenemase?

A

KPC-1

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16
Q

MRSA resistance is due to _____.

A

a new PBP called PBP2a

17
Q

What gene encodes MRSA resistance?

A

mecA gene

18
Q

What prevents the binding of vancomycin to VREs?

A

The swap of terminal D-alanine to D-lactate

19
Q

What genes does the VRE plasmid encode?

A

vanA and vanB