Lecture 7 - Antibacterial Resistance

Question 1

What are the two big factors that are playing against us in the fight against bacteria in regards to antibiotics and resistance?

Answer 1

bacterial is quickly building up resistance to the antibiotics that we have today and fewer antibiotics are being made yearly then ever before

Question 2

What is antibacterial resistance?

Answer 2

Ability for a bacteria to growth and multiply within the presence of an antibiotic

Question 3

What are the two methods in which bacteria gain resistance?

Answer 3

Innate + Acquired

Question 4

What is innate resistance, when it comes to antibiotics?

Answer 4

The bacteria has an inherent structure or function that allows it to evade the antibiotic of interest. It’s a characteristic that the bacteria had long before the AB came along.

Question 5

What is acquired resistance, in regards to antibiotics?

Answer 5

Microbe, by some method, obtains the ability to resist the activity of the AB that it was once susceptible to.

Question 6

What are the two basic methods a microbe may acquire resistance to antibiotics?

Answer 6

Mutation + Transfer

Question 7

By what general mechanism is a AB resistance trait moved from one bacteria to another?

Answer 7

Horizontal gene transfer

Question 8

What are the two basic categories that a bacteria will use in order to disrupt the action of an AB?

Answer 8

Prevent the AB from reaching its target
— or —
Modify/Bypass AB’s target

Question 9

What are the five specific ways that a bacteria is able to become resistant to an AB?

Answer 9

Decrease the uptake
Pump the AB out of the cell
Have enzymes that can render the AB inactive
Change the AB target so that it can’t affect it anymore
Make another enzyme to replace the one removed by the AB

Question 10

Describe the mechanism that the bacteria uses to stop the bacteria from entering the cell.

Answer 10

Changes the structure of its porins that are found in the cell wall. Therefore the AB can no longer enter the cell.

Question 11

When does modifying porins not work for the bacteria?

Answer 11

If the AB’s target is on the cell wall itself

Question 12

Why does efflux pumps work as a method of antibiotic resistance?

Answer 12

It keeps the concentration of AB in the cell so low that it is unable to harm the bacteria enough to kill it.

Question 13

What are the four important enzymes that a bacteria can have that will render the antibiotic useless?

Answer 13

B-lactamase
N-acetyltransferase
O-adenyltransferase
O-phosphotransferase

Question 14

What is important about B-lactamase?

Answer 14

It is responsible for penicillin resistance

Question 15

How is resistance induced?

Answer 15

NOT BY THE ANTIBIOTIC but instead by the environment the AB creates

Question 16

What are the three important habits that will slow AB resistance?

Answer 16

Rx AB’s for bacterial infections only
Educate clients on proper use of AB’s
Make sure you are using the right AB for the right infection

Question 17

Why is it important to not use AB in a patient that has something wrong other than a bacterial infection?

Answer 17

If you give AB’s it could kill the good microflora which is creating a barrier, possibly keeping most of the bad things out. With this barrier gone you can make your sick patient much sicker. = increased virulence of pathogen

Question 18

What should be done to make sure that you are using the correct antibiotic?

Answer 18

Antibiotic susceptibility testing

Question 19

What three things should be documented by for every antibiotic RX?

Answer 19

Dose + Duration + Indiication

Question 20

What are the three most common antibiotic susceptibility tests?

Answer 20

Broth dilution
Disk diffusion
E-Tests

Question 21

What is another name for the disk diffusion method?

Answer 21

Kirby-Bauer

Question 22

What are the basic steps in the Kirby-Bauer method?

Answer 22

Mueller-Hinton agar is evenly covered in bacteria
Filter paper discs with differing ABs are placed over the dish
Plate is incubated

Question 23

How does one read a Kirby-Bauer test?

Answer 23

measure diameter of the “zones of inhibition”

compare to standardized charts

Question 24

What does the kirby-bauer method tell you?

Answer 24

Whether the bacteria is:

Resistant + Susceptible + Intermediate Susceptibility

Question 25

Is the disk diffusion method qualitative or quanitative?

Answer 25

Qualitative

Question 26

What two results can you get from the broth dilution method?

Answer 26

MIC + MBC

Question 27

What is MIC?

Answer 27

Minimum inhibitory concentration

Question 28

What is MBC?

Answer 28

Minimum Bactericidal Concentration

Question 29

How is MIC determined via the broth dilution method?

Answer 29

Serial dilution of an AB is done with standard suspension of bacteria
The tube of lowest concentration that is clear = MIC

Question 30

How is MBC determined using the broth dilution method?

Answer 30

All clear tubes are plated - the lowest concentration with no growth = MBC

Question 31

Is broth dilution method qualitative or quantitative?

Answer 31

Quantitative

Question 32

What exactly does MBC tell you?

Answer 32

The lowest concentration at which the antibiotic kills 99.9% of cells

Question 33

What is the E-test?

Answer 33

Bacteria is evenly covering the plate

Strips with antibiotic at decreasing concentration are placed on agar

Question 34

What does the E-test tell you?

Answer 34

MIC

Question 35

What is the big picture when it comes to preventing antibacterial resistance?

Answer 35

If resistance continues in the same way it is today, one day antibiotics may be useless in the fight against infection.