AM- Mechanisms of Resistance and Issues Flashcards
What are the types of resistance?
Inherent or intrinsic
What may all strains of a given species be?
Examples?
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)
What may be present in some strains of a species but not in others?
- Acquired resistance.
- Labaratory sensitivity testing is required to establish the sensitivity of any bacteria isolate from a patient
How can resistance be acquired? (2 ways)
- Spontaneous mutation
- Spread of resistance
How does spontaneous mutation give acquired resistance?
Change in structure or function which no longer allows the antibiotic to act
How does spread of resistance give acquired resistance?
The gene/s that code for resistance can spread from organism to organism or from species to species
What are current issues in antibiotic resistance?
B-lactamase production
- Bacterial enzymes which cleave the B-lactam ring of the antibiotic and renders it inactive
How are B-lactamase produced (2 ways)
- Most hospital strains of Staphylococcus aureus produce B-lactamase.
- B-lactamases are also common in Gram-Negative bacilli
What are 2 ways to combat B-lactamase?
- Co-amoxiclav
- Flucloxacillin
What is the second issue related to antibiotic resistance?
- Carbapenemase Producing Enterobacteriaceae (CPE) or Carbapenem Resistant Enterobacteriaciae (CRE)
- extremely resistant gram-negative organisms to the carbapanems
What are highly effective antibiotic agents?
Carbapanems which are used for the treatment of severe or high risk bacterial infections
What are all the issues related to antibiotic resistance?
- B-lactamase production
- Carbapenemase Producing Enterobacteriaceae (CPE) or Carbapenem Resistant Enterobacteriaciae (CRE)
- Alteration of penicillin binding protein (PBP) target site
- Glycopeptide resistance
How is the alteration of penicillin binding protein (PBP) target site an issue in antibiotic resistance?
- 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
Where is alteration of penicillin binding protein found?
Any strain of S.aureus that has developed through horizontal gene transfer and natural selection
How is glycopeptide resistance an issu in antibiotic resistance?
- Vancomycin
- Vancomyin resistant enterococci have emerged
- In Vancomycin resistant enterococci , the peptidoglycan precursor to which vancomycin normally binds to has an altered structure