Resistance To Antimicrobial Agents

Question 1

Name the main sites of action of main antibiotics

Answer 1

Cell wall
Plasma membrane
Ribosomes
Metabolic pathways
DNA/RNA synthesis

Question 2

How do antimicrobials become resistance to antibiotics?

Answer 2

• Innate resistance (insensitivity)
• Mutation
• Phenotypic adaptation
• Acquisition of Antibiotic resistance genes –

Question 3

Which type of bacteria is more resistant to antiobitocs and why?

Answer 3

Gram negative as they have an outer membrane that works as a protective barrier

Question 4

What are the 4 main mechanisms of how bacteria escape anti microbes

Answer 4

– Inactivation of antibiotic
– Active efflux of antibiotic
– Alteration of target site
– Metabolic bypass

Question 5

Example of inactivation of what antibiotic

Answer 5

Inactivation of beta-lactams such as penicillin and carbapenems

Question 6

Inactivation of antibiotic:
Enzymes that break down b-lactam antibiotics
-2 ways in which they work
-features

Answer 6

b-lacatmase
1. hydrolyse a specific bond in b-lactam and inactivate
2. Modify antibiotic by adding a chemical group

-many different types
-occur in both gram +ve and gram -ve

Question 7

Ways in which we have tried to combat b-lactamases
-example
-are these effective

Answer 7

-Make a b-lactamase resistant b-lactam
E.g methicillin

-include inhibitor in mix that is a b-lactamase inhibitor
E.g tazobactam

We’re effective but not effective against newer b-lactamases

Question 8

Give an example of a chemical group added during chemical modification of antibiotic

Answer 8

Aminoglycosides:
Gentamicin, tobramycin, amikacin, kanamycin, streptomycin

Question 9

Active reflux of antiobitoics
-how does this work

Answer 9

Use of efflux pump;
Protein sent by bacteria actively pumps antibiotic out of cytoplasm of bacteria so it never reaches inhibitory concentrations

Question 10

Ways of transferring antibiotic resistance gene from one bacteria to another

Answer 10

Transduction
Transformation
Conjugation- transfer of plasmid with the gene from one bacteria to another (most common)

Question 11

How does a plasmid evolve to confer multi-drug resistance

Answer 11

Many of the antibiotic resistance genes are present on transposons

Question 12

Methicillin-resistant staph. aureus (MRSA)

Answer 12

-gram positive bacteria
-Acquired a new penicillin binding protein gene called mecA
-MecA codes for different penicillin binding proteins (PB2a) from another organism
-doesn’t bind any b-lactams; resistant to them all
-mecA carried on mobile genetic element called staphylococcal cassette chromosome mec (SCCmec)
• Many variants
• May carry additional antibiotic resistance genes

Question 13

Most worrying MRSA right now

Answer 13

Livestock-Associated (LA)-MRSA

Question 14

Polymyxins
-which type of thi is used most often
-what are these and how do they work

Answer 14

-colistin
-type of old drug which fell out of use until recently due to its toxicity
-peptide antibiotics that disrupt membrane in gram negative bacteria

Question 15

What can we do to stop antibiotic resistance rising?

Answer 15

• Stop inappropriate use of antibiotics in humans, animals and plants
– Rapid microbe ID + antibiotic sens
– Global
● No OTC antibiotics
● Ban use of antibiotics as growth promoters,
prophylaxis
Control release of antibiotics into the environment
• Invest in identification and development of new antibiotics
• Invest in identification and development of alternatives to antibiotics