Chapter 10: Antimicrobial Medications: Part 2

Question 1

Susceptibility of organisms to specific antimicrobials is ________

Answer 1

Unpredictable

Question 2

How, in the past, were drugs testes?

Answer 2

Often drug after drug tried until favorable response was observed, in a serious infection, several drugs were prescribed at one time with hope that one was effective

Question 3

Better approach to prescribing drugs

Answer 3

• Determine susceptibility

- Prescribe drug that acts against offending organism (best to choose one that effects as few others as possible)

Question 4

MIC

Answer 4

Minimum inhibitory concentration

Question 5

What is MIC?

Answer 5

Quantitative test to determine the lowest concentration of specific antimicrobial drug needed to prevent growth of a specific organism

Question 6

MIC is determined by..

Answer 6

Examining strain’s ability to grow in broth containing different concentrations of test drug

Question 7

MIC is determined by producing..

Answer 7

Serial dilutions with decreasing concentration of test drug

Question 8

Next steps of MIC

Answer 8

• Known concentrations of organism is added to each tube
• Tubes are incubated and examined for growth (determined by turbidity of growth medium)
• Lowest concentration to prevent growth is MIC

Question 9

Kirby-Bauer Disc Diffusion method

Answer 9

Used to qualitatively determine susceptibility

Question 10

IN the Kirby-Bauer method, a clear ______ __ __________ reflects susceptibility

Answer 10

Zone of inhibition

Question 11

In the Kirby-Bauer method, based on size of zone, organism can be describes as _______ or _________

Answer 11

Susceptible

Resistant

Question 12

Mechanisms of resistance to antimicrobial drugs

Answer 12

Drug inactivating enzymes

Alteration of target molecule

Question 13

Drug inactivating enzymes

Answer 13

Some organisms produce enzymes that can chemically modify drug (Penicillinase breaks Beta lactam ring of penicillin antibiotics)

Question 14

Alteration of target molecule

Answer 14

Minor structural changes in antibiotic target can prevent binding (changes in ribosomal RNA prevent macrocodes from binding to ribosomal subunits)

Question 15

Acquisition of resistance can be due to,,

Answer 15

Spontaneous generation or acquisition of new genes

Question 16

Spontaneous mutation

Answer 16

Called vertical evolution, alteration of existing genes(Point mutations, frameshift mutations, etc)

Question 17

Acquisition of new genes

Answer 17

Resistance acquired by transfer of new genes called HORIZONTAL transfer (conjugation, etc)

Question 18

Staphylococcus aureus

Answer 18

Common cause of nosocomial infections

Question 19

Staphylococcus aureus is becoming…

Answer 19

Increasingly resistant (In past 50 years most strains acquired resistance to penicillin)

Question 20

The resistance of Staphylococcus aureus is due to..

Answer 20

Aqcuisition of penicillinase genes

Question 21

What is methicillin?

Answer 21

Penicillinase resistant penicillin

Question 22

MRSA

Answer 22

Methicillin resistant Staphylococcus aureus

Question 23

VISA

Answer 23

Vancomycin intermediate Staphylococcus aureus

Question 24

Responsibilities of physicians and healthcare workers to slow emergence and spread of resistance

Answer 24

Increase efforts to prescribe antibiotics for specific organisms
Educate patients on proper use of antibiotics

Question 25

Responsibilities of patients to slow emergence and spread of resistance

Answer 25

Follow instructions carefully

Complete prescribed course of treatment (misuse leads to resistance)

Question 26

Available antiviral drugs

Answer 26

• Effective for specific types of viruses

- None eliminate latent (dormant) viruses

Question 27

Targets of antiviral drugs include

Answer 27

• Viral uncoating
• Nucleoside analogs
• Non-nucleoside polymerase inhibitors
• Non-nucleoside reverse transcriptase inhibitors
• Protease inhibitors
• Neuraminidase inhibitors