Resistance to Antibiotics

Question 1

natural resistance

Answer 1

• chromosomally mediated and is predictable
• innate
• structural or functional characteristics

Question 2

mutational resistance

Answer 2

• random mutation

- secondary resistance occurring after therapy with the antimicrobial agent in question has begun

Question 3

transferable resistance

Answer 3

• plasmid mediated through
• conjugation
• transduction
• transformation
• horizontal gene transfer

Question 4

transposons

Answer 4

• genetic element
• can’t self replicate
• translocate as unit from one chromosome to another or between chromosome and plasmid or phage
• code functional genes
• flanked by identical short seq-inverted repeats

Question 5

insertion

Answer 5

• can’t self replicate
• transferred
• don’t encode genes
• encodes functions involved in insertion events and contain promoter seq
• -flanked by identical short seq-inverted repeats

Question 6

integrons

Answer 6

• mobile DNA elements with ability to capture genes-resistance-site specific recom
• genes that are captured on are gene cassettes (circular protected DNA)
• recom hot spot
• own integrase function and has efficient promoter site near 5’ end
• as gene gets farther from promoter, expression go down-can be moved closer to promoter to increase expression

Question 7

mechanisms of antibiotic resistance

Answer 7

• enzymatic inactivation
• decreased perm
• efflux
• alteration of target site
• protection of target site
• overproduction of target site
• bypass inhibited process

Question 8

decreased perm

Answer 8

• passage of antibiotics normally through porins
• bigger is more neg-less likely to penetrate
• mutations in porins-increased resistance
• resistance to aminoglycosides and carbapenems is associated with lack of production of outer membrane proteins

Question 9

efflux

Answer 9

tetracyclines
-macrolides and streptogramins
fluoroquinolones

Question 10

altered target sites

Answer 10

tetra, macro, lincosamides, aminoglycosides-failure of ribosomal binding site

Question 11

alteration of cell wall-VRE

Answer 11

-e faecalis-alteration to cell wall- vanco can’t bind

Question 12

alteration of target enzymes

Answer 12

• b lactams-bind to PBP- alteration of PBP can lead to resistance
• MRSA-mecA gene

Question 13

protection of target sites

Answer 13

-tetra-can’t bind

Question 14

overproduction

Answer 14

sulfonamides and trimethoprim

Question 15

bypass inhibition

Answer 15

• auxotrophs. growth factors different
• enterococci
• change in thymidylate synthase-highly resistant to sulfa

Question 16

binding of antibiotic

Answer 16

• VISA

- traps vanco