AM - Antibiotic Resistance Lecture 2 Flashcards

1
Q

What are the 4 types of antibiotic resistance?

A
  • Antibiotic Deactivation
  • Altering target site structure
  • blocking drug from crossing cell wall
  • actively pumping the drug out the cell
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2
Q

How do B-Lactamases work?

A

B-Lactamases are bacterial enzymes that cleave the B-lactam ring of B-lactam antibiotics

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3
Q

Whats the worst type of B-lacatamase?

A

Extended Spectrum B-Lactamases (ESBLs)
produced by some gram -ve organisms & makes them resistant to all b-lactams.

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4
Q

What are the 2 ways we combat B-lactamases?

A
  • Combine the antibiotic with a B-lactamse inhibitor
    And Modify the R1 side chain makin the antibiotic resistant to B-lactamase
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5
Q

Example of an antibiotic with a B-lactamase inhibitor?

A

Co-Amoxiclav

Contains Amoxicillin & Clavulanic acid (the inhibitor)

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6
Q

Example of an antibiotic with a modified R1 side chain?

A

Flucloxacillin (a modified penicillin)

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7
Q

What are CPE?

A

Carbepenemase Producing Enterobacteria.

Gram -ve organisms resistant to carbapenems

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8
Q

Why is CPE so bad?

A

CPEs are often resistant to all relevant antibiotics leaving no therapy options

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9
Q

Why is it dangerous to be hospitalized abroad?

A

Because CPE is endemic in healthcare facilities in some countries.

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10
Q

What are the 2 main ways AMs alter the target site?

A
  • Altering PBP target site

- Altering Peptidoglycan precursor structure

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11
Q

Bacteria with altered PBP structure are resistant to which antibiotics?

A

B-Lactams

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12
Q

Why dont B-lactamase inhibitors help treat when theres altered PBP target site structure?

A

Because theres no B-lactamase involved

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13
Q

Example of bacteria with altered PBP target sites?

A

MRSA

some penicillin resistant Strep. Pneumoniae

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14
Q

bacteria with altered peptidoglycan precursor structure resist what kind of AM?

A

Glycopeptides that target peptidoglycan precursors

E.g. Vancomycin resistant entroccoccus. VRE

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15
Q

Examples of Vancomycin Resistant Enterococci [VRE]?

A

Enterococcus Faecalis & Enterococcus Faecium

Vancomycin resistance is still unusual in gram +ve organisms & VREs have only appeared recently.

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16
Q

When is a bacteria declared resistant?

A

When its unlikely to react to attainable levels of the drug in tissues

17
Q

How do we tell if a bacteria is sensitive to a drug?

A

Antibiotic sensitivity can be lab measured

18
Q

2 types of bacterial resistance?

A
  • Intrinsic/Inherent

- Acquired Resistance

19
Q

Detail intrinsic bacterial resistance?

A
  • All strains of a species are resistant
  • Lab sensitivity testing is irrelevent
  • Usually occurs because the drug cant penetrate the cell wall
20
Q

What kind of bacteria most often show inherent bacterial resistance?

A

Gram -ve Bacteria to Vancomycin

Streptococci to Aminoglycosides

21
Q

What is acquired bacterial resistance?

A
  • Some strains are resistant (e.g. 30% of E.Coli are resistant to Ampicillin)
22
Q

How can acquired resistance be acquired?

A
  • Spontaneous mutation alters bacterial structure/function & prevents antibiotic from working
  • Plasmids & Transposons carry resistance-coding DNA form organism to organism.
23
Q

Note:

Resistant strains only flourish above normal ones when they have a selective advantage

A

Therefore:

Less Antibiotic Use = Less Selective Advantage = Less Resistant Strains