Antibiotics 3

Question 1

Define antibiotic resistance [1]

Answer 1

when microorganisms (such as bacteria, viruses, fungi and parasites) change in ways that render the medications used to cure the infection they cause, ineffective

Question 2

What are the causes of antibiotic resistance and recurring infection? [7]

Answer 2

1. New patterns of travel (air) and trade (especially food)
2. Developments in agricultural practices/animal husbandry
3. Sexual behaviour
4. Medical interventions/developments in medical technology
5. Increasing populations at extremes of age
6. Over/unnecessary use of antibiotics
7. The breakdown of economic, social and political systems

Question 3

Define sepsis [1]

Answer 3

the presence of likely or confirmed infection in addition to the presence of organ dysfunction suggesting an abnormal physiological response to the infection

Question 4

What are 8 mechanisms of resistance shown in the gram-negative bacterium? [8]

Answer 4

1. The loss of porins
2. The presence of ß-lactamases in the periplasmic space
3. Increased expression of the transmembrane efflux pump,
4. The presence of antibiotic-modifying enzymes
5. Target site mutations
6. Ribosomal mutations or modifications
7. Metabolic bypass mechanisms
8. A mutation in the lipopolysaccharide

Question 5

How does the loss of porins contribute to bacterial resistance to drugs? [1]

Answer 5

reduces the movement of drug through the cell membrane

Question 6

How does the presence of β-lactamases in the periplasmic space contribute to bacterial resistance to drugs? [1]

Answer 6

degrades the β-lactam

Question 7

How does increased expression of the transmembrane efflux pump contribute to bacterial resistance to drugs? [1]

Answer 7

it expels the drug from the bacterium before it can have an effect

Question 8

How does the presence of antibiotic-modifying enzymes contribute to bacterial resistance to drugs? [1]

Answer 8

makes the antibiotic incapable of interacting with its target

Question 9

How do target site mutations contribute to bacterial resistance to drugs? [1]

Answer 9

prevent the antibiotic from binding to its site of action

Question 10

How do ribosomal mutations or modifications contribute to bacterial resistance to drugs? [1]

Answer 10

uses an alternative resistant enzyme to bypass the inhibitory effect of the antibiotic

Question 11

How does a mutation in the lipopolysaccharide contribute to bacterial resistance to drugs? [1]

Answer 11

renders the polymyxin class of antibiotics unable to bind this target

Question 12

Outline the 4 chromosomal mechanisms by which bacteria acquire this resistance [4]

Answer 12

1. Chromosome mutation
2. Acquisition of mobile pieces of DNA such as plasmid/integrons/transposon etc
3. DNA uptake through transformation
4. Pieces of DNA transferred between bacteria and viruses (transduction)

Question 13

What is vertical and horizontal gene transfer? [2]

Answer 13

1. Vertical → genetic information is passed from parent cell to progeny through binary fission
2. Horizontal → Genes transferred through anything other than traditional reproduction (this is the primary reason for antibiotic resistance)

Question 14

Which 2 drugs do you give for the treatment for pseudomonas? [2]

Answer 14

1. Tazocin
2. Gentamicin

Question 15

What is fitness cost and what is selection pressure? [2]

Answer 15

1. Fitness cost
   
   • new genetic material means ↓ growth rate
2. Selection pressure
   
   • the use of a range of antibiotics in order to ensure that resistance mutations are less likely to persist in a bacterial population

Question 16

What is the screening test for MRSA? [1]

Answer 16

swab of nose perineum

Question 17

By what mechanism do beta-lactamase enzymes work? [1]

Answer 17

they hydrolyse the β-lactam ring of penicillins and cephalosporins

Question 18

What are the 2 mechanisms for Carbapenem resistance? [2]

Answer 18

1. Porin loss
2. Increased production of beta-lactamase known as AmpC

Question 19

List 3 non genetic mechanisms of resistance antibiotics [3]

Answer 19

1. The body tries to close off an infection but it can’t fight leading to the formation of abscess & granuloma
2. TB needs long treatment since the bacteria don’t divide as they’re in a resting state and so it makes them less susceptible to penicillins and cephalosporins → looks like apparent resistance
3. The immune system is not as effective in the presence of a foreign body which can lead to apparent resistance

Question 20

Where are biofilms seen? [1]

Answer 20

on the surface of a prosthetic joint

Question 21

List 3 ways biofilms can lead to resistance [3]

Answer 21

1. Close proximity of all bacteria means easy gene exchange
2. Channels that exist for O₂, H₂O and nutrient transfer are often too small for antibiotics to penetrate
3. Bottom of biofilm replicates slower → so less susceptible to cell wall agents