MICR-4423 UNIT 4 QUESTIONS AND ANSWERS
How do we define antibiotic resistance? - Answers - Continued growth of bacterial cells
in the presence of an antibiotic that would normally stop growth or kill the cells
What are the 4 main ways that bacterial cells can achieve antibiotic resistance? Give an
example of a mechanism for each way. - Answers - - Block import
-- alteration of the porins in the outer membrane of gram negative cells so that they are
more restrictive
- Efflux
-- efflux pumps
- Modify or destroy the antibiotic
-- beta-lactamases
- Target modification
-- point mutations
What is innate resistance to antibiotics? - Answers - Resistance of antibiotic producers
What is one way that an antibiotic producer can protect itself from the antibiotics it
makes? - Answers - - Make an efflux pump or protective protein at the same time as the
antibiotic
- Complete the last step of biosynthesis outside the cell
What is the difference between genetic and non-genetic resistance? - Answers -
Genetic: semi-permanent
non-Genetic: temporary
What are two examples of non-genetic antibiotic resistance? - Answers - - persistence
- biofilm formation
- tolerance
How does resistance compare to tolerance and persistence? - Answers - Resistance is
typically genetic and allows cells to grow and thrive in the presence of antibiotics.
Tolerance and persistence allow cells to survive transient exposure.
Tolerance usually applies to the entire population and is mediated by environmental
effects or genetic effects, and causes cells to grow more slowly as a population.
Persistence is a small sub-population of cells that is not growing so it can survive
antibiotics
What is meant by the resistome? - Answers - All the resistance genes/mechanisms that
are out there
, What is acquired resistance to antibiotics? - Answers - Resistance of non-antibiotic
producers
How can acquired resistance be acquired by cells? - Answers - - spontaneous
mutations
- horizontal gene transfer
What are some common means by which antibiotic resistance genes can be acquired
by cells? - Answers - - ucompetence
- bacterial conjugation
- phase transduction
What are the ESKAPE pathogens and why are they important? - Answers - E-
Enterococcus faecium
S- Staph aureus
K- Klebsiella pneumoniae
A- Acinetobacter baumannii
P- pseudomonas aeruginosa
E- enterobacter sp.
Important because they are often resistant to a variety of antibiotics
What is the most common mechanism of resistance to β-lactam antibiotics? - Answers -
Beta-lactamases
What is the principal difference between transpeptidases and β-lactamases with respect
to enzyme acyl intermediate lifetimes? What step makes all the difference? - Answers -
Deacylation step***
Transpeptidase: Forms intermediate quickly, but then takes hours to come off... This
ties up the transpeptidase so it can't do its job
Beta-Lactamase: Binds quickly but is then immediately kicked off the enzyme. Purpose
of the beta-lactamase is to break down the beta-lactam
Where must β-lactamases be in the cell for them to do their job of inactivating β-lactam
antibiotics? - Answers - Secreted into the periplasm (gram negative)
On the outer face of the cytoplasmic membrane (g neg or pos)
What are the components of the BlaZ regulation system that induces β-lactamase
production only in the presence of β-lactam antibiotics? What happens to activate the
system? - Answers - BlaR: Transmembrane sensor
Bla-i: Repressor
BlaZ: beta-lactamase
BlaR senses the beta-lactam (outside the cell) and cleaves itself so that the inner part
(BlaR2) can go and degrade the BlaI repressor, which allows for the transcription of
BlaZ, and translation to make the beta-lactamase protein.
How do we define antibiotic resistance? - Answers - Continued growth of bacterial cells
in the presence of an antibiotic that would normally stop growth or kill the cells
What are the 4 main ways that bacterial cells can achieve antibiotic resistance? Give an
example of a mechanism for each way. - Answers - - Block import
-- alteration of the porins in the outer membrane of gram negative cells so that they are
more restrictive
- Efflux
-- efflux pumps
- Modify or destroy the antibiotic
-- beta-lactamases
- Target modification
-- point mutations
What is innate resistance to antibiotics? - Answers - Resistance of antibiotic producers
What is one way that an antibiotic producer can protect itself from the antibiotics it
makes? - Answers - - Make an efflux pump or protective protein at the same time as the
antibiotic
- Complete the last step of biosynthesis outside the cell
What is the difference between genetic and non-genetic resistance? - Answers -
Genetic: semi-permanent
non-Genetic: temporary
What are two examples of non-genetic antibiotic resistance? - Answers - - persistence
- biofilm formation
- tolerance
How does resistance compare to tolerance and persistence? - Answers - Resistance is
typically genetic and allows cells to grow and thrive in the presence of antibiotics.
Tolerance and persistence allow cells to survive transient exposure.
Tolerance usually applies to the entire population and is mediated by environmental
effects or genetic effects, and causes cells to grow more slowly as a population.
Persistence is a small sub-population of cells that is not growing so it can survive
antibiotics
What is meant by the resistome? - Answers - All the resistance genes/mechanisms that
are out there
, What is acquired resistance to antibiotics? - Answers - Resistance of non-antibiotic
producers
How can acquired resistance be acquired by cells? - Answers - - spontaneous
mutations
- horizontal gene transfer
What are some common means by which antibiotic resistance genes can be acquired
by cells? - Answers - - ucompetence
- bacterial conjugation
- phase transduction
What are the ESKAPE pathogens and why are they important? - Answers - E-
Enterococcus faecium
S- Staph aureus
K- Klebsiella pneumoniae
A- Acinetobacter baumannii
P- pseudomonas aeruginosa
E- enterobacter sp.
Important because they are often resistant to a variety of antibiotics
What is the most common mechanism of resistance to β-lactam antibiotics? - Answers -
Beta-lactamases
What is the principal difference between transpeptidases and β-lactamases with respect
to enzyme acyl intermediate lifetimes? What step makes all the difference? - Answers -
Deacylation step***
Transpeptidase: Forms intermediate quickly, but then takes hours to come off... This
ties up the transpeptidase so it can't do its job
Beta-Lactamase: Binds quickly but is then immediately kicked off the enzyme. Purpose
of the beta-lactamase is to break down the beta-lactam
Where must β-lactamases be in the cell for them to do their job of inactivating β-lactam
antibiotics? - Answers - Secreted into the periplasm (gram negative)
On the outer face of the cytoplasmic membrane (g neg or pos)
What are the components of the BlaZ regulation system that induces β-lactamase
production only in the presence of β-lactam antibiotics? What happens to activate the
system? - Answers - BlaR: Transmembrane sensor
Bla-i: Repressor
BlaZ: beta-lactamase
BlaR senses the beta-lactam (outside the cell) and cleaves itself so that the inner part
(BlaR2) can go and degrade the BlaI repressor, which allows for the transcription of
BlaZ, and translation to make the beta-lactamase protein.
