CP3-8 antibiotic resistance

Question 1

What is selection pressure?

Answer 1

A cause of antibiotic resistance as a result of spontaneous gene mutations in bacteria resulting in an antibiotic resistant gene which acts as a survival advantage. This leads to the growth and propagation of the mutant strain.

Question 2

How does transmission of resistant organisms lead to antibiotic resistance?

Answer 2

Resistant bacteria enter the human microbiome and establish themselves there before transferring resistant genes to other bacteria present in the environment.

Question 3

What is the most likely cause of endogenous infection?

Answer 3

Antibiotic resistant organisms surviving antibiotic treatment/exposure and becoming dominant strains

Question 4

How can ceasing antibiotic exposure help remove resistant bacteria?

Answer 4

Resistance mutations tend to affect bacterial cell functions (e.g. cell wall construction and DNA synthesis) so can be out-completed and replaced by antibiotic sensitive organisms if antibiotics are ceased.

Question 5

How are resistant bacteria identified?

Answer 5

Antimicrobial sensitivity testing
Detection of antimicrobial resistant gene

Question 6

What is a sensitive bacteria?

Answer 6

Bacteria with a low MIC

Question 7

How is antibiotic sensitivity testing done?

Answer 7

By trying to grow the bacteria in the presence of an antibiotic and determining the MIC/measuring the zone of inhibition and comparing it to the correlating breakpoint.

Question 8

What is the MIC breakpoint?

Answer 8

if the MIC of an antibiotic to treat a bacteria is less than the MIC breakpoint for that antibiotic, then it is something we could use as treatment for this bacteria.

Question 9

What is the main test used to detect antibiotic resistance genes?

Answer 9

Nucleic acid amplification tests (usually using PCR)

Question 10

What are advantages of nucleic acid amplification testing?

Answer 10

Can be applied to any sample e.g. MRSA testing in nose and skin
Sensitive
Fast

Question 11

What is a disadvantage of nucleic acid amplification testing?

Answer 11

Presence of a gene doesn’t always correlate with resistance e.g. gene is not turned on

Question 12

What property can cause a bacteria to be innately resistant to antibiotics?

Answer 12

The low permeability/entry of the antibiotic into the cell

Question 13

What are examples of antibiotics that are ineffective due to decreased permeability of target bacteria?

Answer 13

Vancomycin on gram - bacilli
Gentamicin on anaerobic organisms

Question 14

What are examples of antibiotics that are ineffective due to modification of target in the bacteria?

Answer 14

Flucloxacillin on MRSA
Vancomycin on VRE
Trimethoprim on gram - bacilli

Question 15

What are examples of antibiotics that are ineffective due to enzyme inactivation in the bacteria?

Answer 15

Beta lactamases like penicillins and cephalosporins
Aminoglycosides
Chloraphenicol

Question 16

What are examples of antibiotics which are made ineffective due to drug efflux (i.e. the as bacteria has mechanism to remove it from the cell)?

Answer 16

multiple antibiotics on gram - bacteria
Antifungal triazoles on candida

Question 17

What enables horizontal transfer of resistant genes between bacteria?

Answer 17

Transposons and integrons transfer cassettes of resistant genes between plasmids or plasmid to chromosome

Question 18

What are consequences of antibiotic resistance and the implications on antibiotic use?

Answer 18

Bacterial infections become resistant to their traditional treatment so risk of under treatment. This leads to increased use of expensive, potentially more toxic, and potentially last line treatments.

Question 19

How is antibiotic resistance monitored?

Answer 19

Locally e.g. alert organism surveillance and longitudinal data collection to detect trends
Nationally e.g. longitudinal data collection to inform antibiotic policies
Internationally

Question 20

What antibiotic has high resistance seen in the Indian supcontinent?

Answer 20

Carbapenem

Question 21

Where in Europe is antibiotic resistance highest? Why?

Answer 21

Southern Europe due to easier access to antibiotics