Lecture 7: Antibacterial Resistance

Question 1

What is antibacterial resistance

Answer 1

Ability of a bacterium to survive and multiple in the presence of an antibiotic

Question 2

What is innate/intrinsic resistance

Answer 2

Innate ability of bacterial species to resist activity of antibiotic through its inherent structural or functional characteristics

Chromosomally encoded, relates to general physiology

Question 3

What is acquired/ extrinsic resistance

Answer 3

Organism obtains the ability to resist the activity of an antibiotic to which it was previously susceptible

Mutation in resident gene
Transfer of genetic material through horizontal or vertical gene transfer

Question 4

What is transformation

Answer 4

Uptake of naked DNA from a donor cell to a recipient cell

Question 5

What is transduction

Answer 5

Phage mediated transfer of bacterial DNA from donor to recipient

Question 6

What is conjugation

Answer 6

Transfer of plasmid DNA from a donor to a recipient during cell to cell contact

Question 7

What are the two main reasons why antibiotic resistance is a huge problem

Answer 7

1. Reversing progress of antibiotic development— antibiotics we do have are less effective
2. New antibiotic development has rapidly slowed down

Question 8

How many deaths occur from antibiotic resistant infections each year

Answer 8

23,000

Question 9

What is the annual cost of antibiotic resistant infections

Answer 9

$20 billion

Question 10

Many bacteria that are antibiotic resistant are found in ___

Answer 10

Livestock

Question 11

Antibiotic use selects for drug resistant organisms. ___ is not induced by antibiotic itself but by the ___ created by antibiotics

Answer 11

Resistant, environment

Question 12

To survive the presence of antibiotic bacterial organisms must be able to do ___ or ____ of the antibiotic

Answer 12

Disrupt or prevent the action of the antibiotic

Question 13

What are the 5 bacterial resistant strategies

Answer 13

1. Decreased uptake/ block entry
2. Efflux pumps
3. Inactivating enzymes
4. Target alterations
5. Alternative enzyme

Question 14

What is one alteration bacterial cells can make to reduce the uptake of antibiotics

Answer 14

Altering porins

Question 15

What is the effect of efflux pumps

Answer 15

Pump out antibiotics to decrease the concentration inside the cell thus it is too low to elicit an effect

Question 16

How do bacterial cells produce antibiotic inactivation by modification or degradation

Answer 16

Use enzymes that can degrade or modify antibiotic so it is no longer effective

Question 17

How does B-lactamase work

Answer 17

Bind and make bacteria resistant to B-lactam antibiotics (penicillin, cephalosporins)

Question 18

What is the purpose of B-lactamase inhibitors

Answer 18

Inhibit the activity of B-lacatamse to extend the activity spectrum of B-lactam antibiotics

Question 19

What is the purpose of bacteria modifying the antimicrobial target

Answer 19

Use acquired mutations or modified structures that are no longer recognized by antibiotic

Question 20

How can bacterial cells bypass the antibiotic target

Answer 20

Acquired a new enzyme that allows bypass of metabolism pathway

Question 21

What are ways we can slow down resistance

Answer 21

1. Prescribe antibiotics for bacterial infections only
2. Educate clients on proper use of antibiotics
3. Determine most appropriate antibiotic

Question 22

Important to prescribe antibiotics for bacterial infections, if prescribed for viral infections what happens

Answer 22

Decrease normal flora and could increase susceptibility to other pathogens

Question 23

Why is it important to finish course of antibiotics

Answer 23

Need to kill all bacteria, if you stop it early you are leaving behind some bacteria that can then develop resistance to that antibiotic

Question 24

What are 3 tests we can do to determine correct antibiotic to use

Answer 24

1. Disk diffusion/ Kirby Bauer method
2. Broth dilution (MIC)
3. E-tests

Question 25

How does a disk diffusion/ Kirby Bauer test work

Answer 25

1. Use mueller-Hinton agar plates
2. Filter plates with antibiotics placed on plate- highest concentration of antibiotic is around the disk
3. After incubation the diameters of the zones of inhibition surrounding the disk are measures
4. Compared to standardized chart to determine antibiotic that bacteria was most sensitive to

Question 26

How does the broth dilution (MIC) method work

Answer 26

1. Serial dilution of antibiotics
2. Determine lowest concentration of antibiotic that inhibits bacterial growth is the MIC- minimum inhibitory concentration

• can also use micropipeter plate- same principle

Question 27

How do you determine the MBC- maximum bactericidal concentration

Answer 27

1. Take aliquot from each tube without any growth from broth dilution and plate it onto antibiotics free plate and incubate
2. Lowest concentration kills 99% of bacterial cells- no growth on agar plate

Question 28

How does the E-test work

Answer 28

1. Combine use of Kirby Bauer/ disk diffusion with ability to determine MIC
2. Use mueller Hinton agar plates that are inoculated with bacterial suspension
3. Plastic trips impregnated with gradually decreased concentration of antibiotic placed on plate
4. After incubation MIC value is determined where the elliptical zone of the inhibition crosses the E-test strip