Antimicrobial Resistance and Susceptibility

Question 1

Which is the most important superbug associated with hospitals?

Answer 1

Carbapenem- resistant K. pneumoniae

Question 2

Which of the following are most common in hospitals and the community, including livestock and companion animals?

a. Methicillin-resistant S. aureus (MRSA)
b. ESBL-producing E. coli
c. Multidrug resistant S. pneumoniae
d. A and C
e. A and B
f. B and C

Answer 2

e. A and B

Question 3

True/ False. Antibiotic therapy is only recommended for invasive infections.

Answer 3

True.

Question 4

Which drugs have a resistance to Salmonella?

Answer 4

Cephalosporins or fluoroquinolones

Question 5

Which drugs have a resistance to Campylobacter?

Answer 5

Macrolides or fluoroquinolones

Question 6

True/ False. MDR (multi drug resistant) bacteria are usually resistant to all drugs except cephalosporins.

Answer 6

False. They are resistant to cephalosporins

Question 7

Which of the following are beta-lactam resistant?

a. MRSA
b. MRSP
c. ESBL
d. All the above

Answer 7

d. All the above

Question 8

What does MRSA stand for?

Answer 8

Methicillin Resistant Staphylococcus Aureus

Question 9

True/False. MRSA and MRSP have the lowest affinity to penicillins and cephalosporins.

Answer 9

True.

Question 10

Which of the following MRSA is associated with livestock?

a. CC8
b. CC22
c. CC398
d. CC9

Answer 10

c. CC398

Question 11

What does MRSP stand for?

Answer 11

Methicillin Resistant Staphylococcus Pseudintermedius

Question 12

True/False. Approximately 70% of MRSP cases are skin and wound postsurgical infections acquired in the clinic.

Answer 12

True.

Question 13

What does ESBL stand for?

Answer 13

Extended Spectrum Beta Lactamase

Question 14

What is ESBL?

Answer 14

It is an enzyme hydrolyzing/inactivating most Beta lactams produced by gram-negative bacteria

Question 15

What is the only beta lactam ESBL does not hydrolyze/inactivate?

Answer 15

Carbapenems

Question 16

True ESBLs are susceptible to B- lactamase inhibitors such as _____.

Answer 16

Clavulanic acid

Question 17

What are the three main ESBL classes?

Answer 17

CTX-M
SHV
TEM

Question 18

Which is the most common type of ESBL in animals?

a. CMY-2
b. CTX-M-2
c. CTX-M-1
d. CMY-1

Answer 18

c. CTX-M-1

Question 19

A false ESBL (resistant to Beta-lactamase inhibitors) is widespread in small animals and limited to poultry

Answer 19

CMY-2

Question 20

Which ESBL type can be transferred horizontally from E.coli livestock to E.coli in humans?

Answer 20

CTX-M-1

Question 21

How do bacteria acquire resistance?

Answer 21

Mutation

Horizontal gene transfer by transformation, transduction, and conjugation

Question 22

What is transduction?

Answer 22

A transfer mediated by phage delivery

Question 23

True/False. Antimicrobial resistance is a qualitative property.

Answer 23

False. Its a quantitative property

Question 24

What are the two dilution methods for AST?

Answer 24

Broth dilution tests

Agar dilution tests

Question 25

What are the two agar diffusion methods for AST?

Answer 25

Disk/tablet diffusion test (semi-quantitative) | Gradient diffusion E test (quantitative)

Question 26

___ is the lowest concentration that inhibits completely growth of the test strain.

Answer 26

MIC (minimum inhibitory concentration)

Question 27

What is MBC (Minimum bactericidal concentration)

Answer 27

The lowest concentration that kills the test strain

Question 28

True/False. Diffusion method has a high reproducibility and robustness, whereas dilution method has a medium reproducibility and robustness.

Answer 28

False. Diffusion method has a MEDIUM reproducibility and robustness, whereas dilution method has a HIGH reproducibility and robustness.

Question 29

Is the dilution method more expensive or cheaper than the diffusion method?

Answer 29

More expensive than diffusion

Question 30

True/False. Standardization and quality control are required for reproducibility of AST.

Answer 30

True.

Question 31

How is quality control done?

Answer 31

- Reference strains of different species are routinely included in the testing (every day, or every week) - MIC of the reference strain has to fall within a given range - If not within a range the test will not be valid and should be repeated

Question 32

What is the incubation period for the AST laboratory test?

Answer 32

35 Degrees C for 16-20 hours

Question 33

What is a breakpoint?

Answer 33

A drug-specific value to interpret the results of susceptibility testing and determine if an antibacterial is potentially useful in the treatment of a bacterial infection.

Question 34

A strain is defined as ___ by a level of antimicrobial activity associated with a high likelihood of therapeutic success.

Answer 34

Susceptible

Question 35

A strain is defined as ___ by a level of antimicrobial activity associated with a high likelihood of therapeutic failure.

Answer 35

Resistant

Question 36

What is the standard range of a susceptible MIC? Resistant MIC?

Answer 36

less than or equal to 4 = susceptible | greater than or equal to 32 = resistant

Question 37

What data is needed for setting breakpoints?

Answer 37

1. MIC distribution to determine MIC value that separates the WT population from resistant populations 2. PD/PK index 3. Clinical and bacteriological outcome data from clinical trials

Question 38

When is a strain defined as wild type (WT) for a species?

Answer 38

By the absence of any acquired resistance genes and/or mutations increasing the MIC of the antimicrobial agent

Question 39

If a strain is ___ for AST, it is inhibited at blood concentrations achieved by standard dosage of the drug.

Answer 39

Susceptible

Question 40

Clinical efficacy is possible if the strain infects body sites where the drug concentrates or if the dosage can be increased compared to standard dosage.

Answer 40

Intermediate

Question 41

Resistant for AST

Answer 41

The strain is NOT inhibited at blood concentrations achieved by standard dosage of the drug.

Question 42

What are the two drugs used for detection of MRSA/MRSP?

Answer 42

Oxacillin | Cefoxitin

Question 43

True/False. Strains resistant to oxacillin/cefoxitin should be regarded as susceptible to all beta lactams.

Answer 43

False. They are resistant to Beta lactams