AM - Antibiotic Resistance Lecture 2

Question 1

What are the 4 types of antibiotic resistance?

Answer 1

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

Question 2

How do B-Lactamases work?

Answer 2

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

Question 3

Whats the worst type of B-lacatamase?

Answer 3

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

Question 4

What are the 2 ways we combat B-lactamases?

Answer 4

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

Question 5

Example of an antibiotic with a B-lactamase inhibitor?

Answer 5

Co-Amoxiclav

Contains Amoxicillin & Clavulanic acid (the inhibitor)

Question 6

Example of an antibiotic with a modified R1 side chain?

Answer 6

Flucloxacillin (a modified penicillin)

Question 7

What are CPE?

Answer 7

Carbepenemase Producing Enterobacteria.

Gram -ve organisms resistant to carbapenems

Question 8

Why is CPE so bad?

Answer 8

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

Question 9

Why is it dangerous to be hospitalized abroad?

Answer 9

Because CPE is endemic in healthcare facilities in some countries.

Question 10

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

Answer 10

• Altering PBP target site

- Altering Peptidoglycan precursor structure

Question 11

Bacteria with altered PBP structure are resistant to which antibiotics?

Answer 11

B-Lactams

Question 12

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

Answer 12

Because theres no B-lactamase involved

Question 13

Example of bacteria with altered PBP target sites?

Answer 13

MRSA

some penicillin resistant Strep. Pneumoniae

Question 14

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

Answer 14

Glycopeptides that target peptidoglycan precursors

E.g. Vancomycin resistant entroccoccus. VRE

Question 15

Examples of Vancomycin Resistant Enterococci [VRE]?

Answer 15

Enterococcus Faecalis & Enterococcus Faecium

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

Question 16

When is a bacteria declared resistant?

Answer 16

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

Question 17

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

Answer 17

Antibiotic sensitivity can be lab measured

Question 18

2 types of bacterial resistance?

Answer 18

• Intrinsic/Inherent

- Acquired Resistance

Question 19

Detail intrinsic bacterial resistance?

Answer 19

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

Question 20

What kind of bacteria most often show inherent bacterial resistance?

Answer 20

Gram -ve Bacteria to Vancomycin

Streptococci to Aminoglycosides

Question 21

What is acquired bacterial resistance?

Answer 21

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

Question 22

How can acquired resistance be acquired?

Answer 22

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

Question 23

Note:

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

Answer 23

Therefore:

Less Antibiotic Use = Less Selective Advantage = Less Resistant Strains