AM- Mechanisms of Resistance and Issues

Question 1

What are the types of resistance?

Answer 1

Inherent or intrinsic

Question 2

What may all strains of a given species be?

Examples?

Answer 2

Naturally resistant to an antibiotic

• Streptococci always resistant to ahminoglycosides
• Gram negative always resistant to Vancomycin (due to the inability of the drug to penetrate the bacterial cell wall to exert its action)

Question 3

What may be present in some strains of a species but not in others?

Answer 3

• Acquired resistance.

- Labaratory sensitivity testing is required to establish the sensitivity of any bacteria isolate from a patient

Question 4

How can resistance be acquired? (2 ways)

Answer 4

• Spontaneous mutation

- Spread of resistance

Question 5

How does spontaneous mutation give acquired resistance?

Answer 5

Change in structure or function which no longer allows the antibiotic to act

Question 6

How does spread of resistance give acquired resistance?

Answer 6

The gene/s that code for resistance can spread from organism to organism or from species to species

Question 7

What are current issues in antibiotic resistance?

Answer 7

B-lactamase production

- Bacterial enzymes which cleave the B-lactam ring of the antibiotic and renders it inactive

Question 8

How are B-lactamase produced (2 ways)

Answer 8

• Most hospital strains of Staphylococcus aureus produce B-lactamase.
• B-lactamases are also common in Gram-Negative bacilli

Question 9

What are 2 ways to combat B-lactamase?

Answer 9

• Co-amoxiclav

- Flucloxacillin

Question 10

What is the second issue related to antibiotic resistance?

Answer 10

• Carbapenemase Producing Enterobacteriaceae (CPE) or Carbapenem Resistant Enterobacteriaciae (CRE)
• extremely resistant gram-negative organisms to the carbapanems

Question 11

What are highly effective antibiotic agents?

Answer 11

Carbapanems which are used for the treatment of severe or high risk bacterial infections

Question 12

What are all the issues related to antibiotic resistance?

Answer 12

• B-lactamase production
• Carbapenemase Producing Enterobacteriaceae (CPE) or Carbapenem Resistant Enterobacteriaciae (CRE)
• Alteration of penicillin binding protein (PBP) target site
• Glycopeptide resistance

Question 13

How is the alteration of penicillin binding protein (PBP) target site an issue in antibiotic resistance?

Answer 13

• Micro-organisms develop resistance to B-lactams by changing the structure of their PBP
• Mutations in PBPs gene result in a modified target site to which B-lactams will no longer bind

Question 14

Where is alteration of penicillin binding protein found?

Answer 14

Any strain of S.aureus that has developed through horizontal gene transfer and natural selection

Question 15

How is glycopeptide resistance an issu in antibiotic resistance?

Answer 15

• Vancomycin
• Vancomyin resistant enterococci have emerged
• In Vancomycin resistant enterococci , the peptidoglycan precursor to which vancomycin normally binds to has an altered structure

Question 16

What can occur in vancomycin resistant enterococci?

Answer 16

This mechanism of resistance might spread from enterococci to S.aureus producing vancomycin resistant S.aureus