Antibiotic resistance

Question 1

What is natural (intrinsic) resistance?

Answer 1

Chromosomally mediated and is predictable

Question 2

What is mutational resistance?

Answer 2

Random mutation; secondary resistance occurring after therapy with the antimicrobial in question has begun

Question 3

What is transferable resistance?

Answer 3

Plasmid-mediated through - conjugation (bacterial mating); transduction (bacteriophage transmission); Transformation (uptake of DNA from environment)

Question 4

What are the two types of transposable genetic elements?

Answer 4

1. Transposons - transposases that allow for transposition (“hopping”) from one location to another independent of the recombination enzymes of the host, 2. insertion sequences (don’t have genes, but have promoter sequences capable of activating the expression of neighboring genes - can activate resistant gene transcription in Staphylococci)

Question 5

What is an integron?

Answer 5

Mobile DNA elements with ability to capture genes - antibiotic resistance genes located on cassettes
- the integron has a promoter sequence and the closer the gene is to the promoter sequence, the more likely it is to be expressed - the expression of the promoterless, cassette-associated resistance genes is markedly influenced by their position in a cassette array

Question 6

There are seven distinct mechanisms of antibiotic resistance:

Answer 6

1. Enzymatic inactivation 2. Decreased permeability 3. efflux 4. alteration of target site 5. protection of target site 6. overproduction of target 7. bypass of inhibited process