8.3 Antibiotics resistance Flashcards Preview

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Flashcards in 8.3 Antibiotics resistance Deck (12):
1

What are plasmids?

Extrachromosomal genetic elements which replicate independently of the chromosome

Often carry genes for antibiotic resistance

2

What is recombination?

integration of plasmids and other DNA into the chromosome

3

What is homologous recombination?

takes place between regions of the same sequence in two different molecules

4

What is site specific recombination?

involves enzymes that integrate new DNA at specific sites in the chromosome

5

What are the types of transmission of resistance?

Transformation
Transduction
Conjugation

6

How does transformation of resistance occur, give an example and what are the limitations

Uptake of naked DNA from the environment and incorporation into the genome

Penicillin resistance of Strep Pneumoniae

Limitations: DNA must be from related bacteria

7

How does transduction of resistance occur, give an example and what are the limitations?

Transfer of DNA from one bacterium to another via bacteriophages. The bacteriophages will insert the DNA into bacteria and as the multiplies the resistance will be passed on

Limitations: transfer of DNA is limited by hosts bacteriophages
Integration of the donor DNA in recipient relies on presence of target sequences for integration which is more likely in related hosts

8

How does conjugation of resistance occur, give an example and what are the limitations?

Transfer of genetic material usually in the form of a plasmid, from one cell to another through cellular contact - usually through plasmids

Not many limitations - can take place between species and clinically the most significant

9

What are the forms of antibiotic resistance?

Drug inactivating enzyme
Alteration in target molecule
Decreased uptake
Increased elimiation

10

What are the forms of S.aureus resistance?

Penicillin: beta lactamase produced by bacteria destroys the beta lactam ring
Methicillin: MecA gene which alters the binding site
Vancomycin: thickening of peptidoglycan wall

11

What is the enterococcus resistance?

Vancomycin - change from D-ala-D-ala to D-lac
VanA = resistant to both glycopeptides (vancomycin and tecioplanin)
VanV = only vancomycin

12

What are the forms of strep pneumoniae resistance?

Penicillin: stepwise increase by acquiring different genes changing the binding proteins

Protein synthesis inhibitors: get mef pump in the 50s for macrolides and rRNA methylase changes in 50s subunit binding site for macrolides and clindamycin