9. Antibiotic resistance

Question 1

define antibiotic resistance

Answer 1

the ability of an organism to resist the action of an antimicrobial drug

Question 2

name 3 ways that increase antimicrobial resistance

Answer 2

• inappropriate use of antibiotics (prescription/ agriculture)
• poor infection prevention and control practise
• antibiotics in water supply

Question 3

what are the two types of resistance

Answer 3

1. intrinsic resistance (naturally occurring)

2. acquired resistance

Question 4

how does intrinsic resistance occur

Answer 4

naturally, due to normal genes the host possesses

Question 5

how does acquired resistance occur

Answer 5

1. induced genetic mutation (Following pressure from antibiotics)
2. acquired: by transfer of genetic material from one bacterium to another via sex pills.

Question 6

how can some microorganisms be resistant to antibiotics: name 3 factors

Answer 6

• lack target binding site: e.g. no peptidoglycan so beta-lactams won’t work
• efflux pump: export the antibiotic outside the cell, e.g. tetracyclines in pseudomonas
• producing an enzyme that inactivates antibiotics: beta lactamases etc

Question 7

how do bacteria in a biofilm resist antibiotics

Answer 7

covered in polymeric substance that prevents antibiotic penetration

Question 8

how are resistance genes transferred in bacteria

Answer 8

exist in plasmids which can then be transferred via conjugation by sex pili

Question 9

how can a phage induce antibiotic resistance in a population

Answer 9

bacteriophage’s are viruses that infect bacterial cells and breakdown the host’s chromosome

sometimes during phage assembly, pieces of the bacterial DNA are packaged into phage genome

the phage then reinfects a cell where recombination can occur = genome with both donor and recipient DNA

Question 10

how are resistant genes transferred during conjugation

Answer 10

in single stranded DNA form, in the recipient cell the complimentary strand is synthesised

Question 11

what does the conjugation process require, so what is ideal for this?

Answer 11

close proximity

biofilms

Question 12

explain how resistance is acquired by transformation

Answer 12

free DNA in the environment is taken up into the cell, recombination occurs = resistant genome

Question 13

what do beta-lactams bind to which weakens the cell wall

Answer 13

bind to penicillin-binding proteins

Question 14

what can be used to treat extended-spectrum beta-lactamases

Answer 14

beta-lactamas inhibitors e.g. ampicillin (clavulanic acid)

Question 15

what lab techniques are used to test resistance

Answer 15

disc diffusion testing = zone of inhibition

PCR

Minimum inhibitory concentration

Question 16

what gene is detected using PCR of MRSA to confer resistance

Answer 16

Mec A gene = resistance