Antibacterial Resistance

Question 1

What is an antibiotic ?

Answer 1

A drug that kills or inhibits the growth of a micro-organism

Question 2

Define resistant

Answer 2

Somewhat arbitrary designation that implies that an antimicrobial will not inhibit bacterial growth that clinically achievable concentrations

Question 3

Define susceptible

Answer 3

Somewhat arbitrary designation that impes that an antimicrobial will inhibit bacterial growth that clinically achievable concentrations

Question 4

What is “MIC”

Answer 4

Minimial inhibitory concentration, lowest concentration of antimicrobial that inhibits growth of bacteria, commonly used in clinical labs

Question 5

what is “MBC”

Answer 5

minimal bactericidal condentration. Concentration of an antimicrobial that kills bacteria. Used clinically only in special circumstances

Question 6

What is breakpoint ?

Answer 6

The MIC that is used to designate between susceptible and resistant. Arbitrarily set by a committee

Question 7

What are the automated ways you can determine the minimial inhibitory concentration ?

Answer 7

You can test using a well plate for MIC testing. You can also use automated testing

Question 8

What are some manual ways you can determine susceptibility ?

Answer 8

Kirby Bauer Disc dilution - Not precise
Agar Dilution- dilution conc in agar to see which conc will inhibit growth
E Test- strip of ABx that has different conc’s as you move down the strip to see the MIC

Question 9

What does antibiotic use lead to ?

Answer 9

Antibiotic resistance

Question 10

What is the break point for determining antibiotic resistance ?

Answer 10

The concentration that has to be achieved to get efficacy for a particular Abx. Any

Question 11

Wgat happens when the MIC is greater than the break point ?

Answer 11

The bacteria will become resistant

Question 12

What is the relationship between break point and MIC for a drug that is susceptible ?

Answer 12

The break point will be much higher than the MIC

Question 13

What is the largest factor that contribues to ABx resistance ?

Answer 13

Abx use is the largest contributing factor. Especially in agriculture because the Abx used on animals can be spread to humans

Question 14

Can resistant bacteria be transmitted between people ?

Answer 14

Yes

Question 15

Is Abx resistance limited to that one Abx ?

Answer 15

No when a bacteria becomes resistant it could potentially be resistnat to numerous strains of bacteria. See bacteria example from lecture

Question 16

What part of the bacterial genome will carry Abx resistance genes ?

Answer 16

The plasmids or chromosomes

Question 17

What are the mechanisms of bacterial enzymatic resistance ?

Answer 17

Sulfonation, phosphorylation, or esterification which is ezpecially a problem for aminoglycosides

Question 18

Why are B Lactamases more potent in gram - bacteria ?

Answer 18

It is located in the periplasmic space. It will have a higher concentration because they are located on the cell wall in Gram ( + ) bacteria.

Question 19

What are B Lactamase capable of ?

Answer 19

They are capable of hydrolysind extended spectrum cephalosproins, penicillins, aztrenonam. They are usually plasma mediated. They are responsable for significant resistance determinate in acute and long term care facility enteric pathogens

Question 20

What are two mechanisms of bacterial resistance that directly affect the bacterial membrane ?

Answer 20

1. Decreased permeability which directly affects carbapenems

Efflux pumps- used promarly by pseudomonas and is effective against Tetracyclines and Macrolides

Question 21

What are some target alterations that will aid in drug resistance .

Answer 21

DNA Gyrase- Fluroquinones and many gram ( - ) bacteria

Penicillin Binding Protein- Methacillin resistant S areus ( MRSA )

Gram Positive cell wall - works against Vanc

Question 22

What are the Glycopeptide resistant strains of A aureus ?

Answer 22

Gycopeptide mediated resistance-

Glycopeptide high level resistance-

Question 23

What is the major factor that is ontributing to antibiotic resistance ?

Answer 23

Inappropriate and excessive use of antibiotics is a major factor contrubuting to amergeing antibiotic resistance

Question 24

What are the determinants of resistance ?

Answer 24

They are selected for by Abx use

Question 25

What is the goal of antibiotic use ?

Answer 25

Prevention or cure of infection with a minimum of toxicity to the patient with minimial impact on the patients microbial flora of that patient and the other patients and environment

Question 26

What is colonization pressure ?

Answer 26

The pressure

Question 27

What are the three principles of antimicrobial resistance?

Answer 27

1. Resistnace is likely to emerge

Question 28

Once you have resistance will it decline?

Answer 28

Once resistance appears it is likely to decine slowly if at all.