mechanism of resistance to antibiotics

Question 1

3 types of resistance

Answer 1

intrinsic
mutational
acquired

Question 2

intrinsic/natural resistance

Answer 2

innate ability of bacteria to resist activity of a particular antimicrobial agents through is inherent structural or functional characteristics

Question 3

mutational resistance

Answer 3

due to spontaneous or random mutation
can occur due to exposure to an antibiotic
will depend on structure and # of genes in which mutations can produce selectable phenotype

Question 4

acquired resistance

Answer 4

occurs when organism obtains to ability to resist the activity of a particular antibiotic in which it was previously susceptible
can occur through horizonal gene transfer

Question 5

location of antimicrobial resistant genes

Answer 5

1. plasmids

2. transposable genetic elements- transposable genetic elements and insertion sequences

Question 6

can transpoons replicate on their own?

can plasmids?

Answer 6

transpoons cannot

plasmids can

Question 7

how do transpoons and insertion sequences differ?

Answer 7

transpoons encode functional genes that mediate a recognizable phenotype (such a antibiotic resistance)
insertion sequences only encode functions involved in insertion events (can contain partial or complete promoter sequences)

Question 8

what are integrons

Answer 8

dna adjacent to antibiotic resistance genes who often have unique integration units called integrons

Question 9

principal role of integrons

Answer 9

provide a convenient insertion site for antibiotic resistance genes from foreign DNA sources

Question 10

the frequency of transcription of integrated cassettes of antibiotic resistance genes depends on?

Answer 10

proximity of the gene to the promoter at the 5` upstream end of the integron

Question 11

what effects the level of expression of a resistance gene?

Answer 11

the distance between the promoter and the specific antibiotic-resistance gene cassette
(level of expression and distance inversely proportionate)

Question 12

list 8 mechanisms in which antibiotic resistance is described in bacteria

Answer 12

enzymatic inactivation
decreased permeability
efflux
alteration of target site
protection of target site
overproduction of target
bypass inhibited process
binding of antibiotic

Question 13

enzyme inactivate example and mechanism

Answer 13

B- lactamases- enzymes that inactivate antibiotics by splitting the amide bond of B-lactam ring

Question 14

what are extended spectrum B-lactamases and what 3 pathogens are the usually associated with

Answer 14

enzymes that mediate resistance to extended spectrum (3rd generation) antibiotics
found on klebsiella, e. coli and proteus

Question 15

patients who exhibit what type of B lactamase is place in isolation like MRSA

Answer 15

extended spectrum

Question 16

carbapenemases can hydrolyze which antibiotics

Answer 16

carbapenems and also broad spectrum penicillins, oxymino-cephalosporins and cephamycins

Question 17

how can you treat an infection due to a beta lactamase producing organism with a beta lactam based antibiotic?

Answer 17

1. penicillin resistant penicillins
2. b- lactamase inhibitors and inhibitor combinations
3. extended spectrum cephalosporins and carbapenams

Question 18

how does altering the target site increase antibiotic resistance

Answer 18

ex. alteration of ribosomal binding sites causes a failure of the antibiotic to bind to its target site on the ribosome and disrupts it ability to inhibit protein synthesis and cell growth
ex2. alteration of cell wall precursor sites
ex3. alteration of target enzymes (MRSA!)

Question 19

how does the bypass of antibiotic inhibition target lead to antibiotic resistance?

Answer 19

by developing auxotrophs which have diff growth factor requirements than wild type

Question 20

mechanism of resistance for VRE

Answer 20

alteration of cell wall precursor target sites

Question 21

what are most common organisms that have amp C B-lactamases?

Answer 21

observed in enterobacteriaceae other than klebsille and e coli
plasmid mediated ampC enzymes on E. coli, K. pneumoniae, salmonella enterica and proteus mirabilis

Question 22

where are carbapenemases seen?

Answer 22

on k. pneumoniae