CHAPTER 10

Question 1

What are drugs?

Answer 1

chemicals that affect physiology in any manner

Question 2

What are chemotherapeutic agents?

Answer 2

drugs that act against disease

Question 3

What are the modes of action of antimicrobials?

Answer 3

inhibition of cell wall synthesis,
block a pathogens attachment to host,
inhibition of protein synthesis,
breakdown of the cell membrane structure or function,
interference with functions of DNA and RNA,
blockage of key metabolic pathways

Question 4

What are the major action modes of antibacterial drugs?

Answer 4

inhibition of cell wall synthesis- ex. penicillins;
inhibition of protein synthesis- ex. tetracyclines;
inhibition of nucleic acid replication and transcription- ex. quinolones;
injury to plasma membrane- ex. polymyxin B;
inhibition of essential metabolite synthesis- ex. sulfanilamide

Question 5

What mode of action has no affect on the existing peptidoglycan layer and only is effective for growing cells?

Answer 5

inhibition of synthesis (on bacterial cell walls)

Question 6

Major drugs targeting bacteria?

Answer 6

isoniazid, polymycin, penicillin, streptomycin, erythromycin, tertracycline, sulfonamides

Question 7

Major drugs targeting fungi?

Answer 7

echinocandins, nystatin, amphotericin B, azoles, allylamines

Question 8

Major drugs targeting vegetative cells?

Answer 8

.

Question 9

Major drugs targeting spores?

Answer 9

.

Question 10

Major drugs targeting protozoa?

Answer 10

atovaquone, azoles

Question 11

Major drugs targeting helminths?

Answer 11

niclosamide, praziquantel

Question 12

Major drugs targeting viruses?

Answer 12

arildone, ribavirin, acyclovir

Question 13

What makes viruses the trickiest targets?

Answer 13

the virus has to attach to host cell, then enter the cell, then uncode its genetic information, and then attack and take over cell. Several processes need to be interfered with which makes it more difficult to target

Question 14

How do we measure resistance?

Answer 14

take sample and put in agar or broth, expose to various drugs and observe if they divide and thrive or not

Question 15

How do we measure effectiveness of a drug?

Answer 15

diffusion susceptibility test, minimum inhibitory concentration test, minimum bactericidal concentration test

Question 16

Why do we need to be careful with antibiotics?

Answer 16

drug toxicity can occur; drugs can be toxic to kidneys, liver, or nerves; need to specifically consider drugs for pregnant women carefully

Question 17

What can go wrong with antibiotics?

Answer 17

allergies, disruption of normal microbiota (causing secondary infections),

Question 18

How can we combat resistance?

Answer 18

maintain high concentration of drug in patient for sufficient time;
use antimicrobial agents in combination (synergism and antagonism)

Question 19

What are the mechanisms of resistance?

Answer 19

blocking entry,
inactivation by enzymes,
alteration of target molecule,
efflux of antibiotic

Question 20

What is synergism?

Answer 20

occurs when one drug enhances the effect of a second drug

Question 21

What is antagonism?

Answer 21

occurs when drugs interfere with each other

Question 22

What is antagonism?

Answer 22

occurs when drugs interfere with each other

Question 23

What are 7 ways microorganisms can be resistant to antimicrobial drugs?

Answer 23

• produce enzyme that destroys or deactivates Slow or prevent entry of drug into the cell
• Alter target of drug so it binds less effectively
• Alter their own metabolic chemistry
• Pump antimicrobial drug out of the cell before it can
act
• Bacteria in biofilms can resist antimicrobials
• Mycobacterium tuberculosis produces MfpA protein

Question 24

What is horizontal gene transfer?

Answer 24

genes transferring from one bacteria to the other

Question 25

What are the ways R plasmids can be acquired in drug resistance?

Answer 25

transformation, transduction, conjugation

Question 26

What is transformation?

Answer 26

transfer of free DNA

Question 27

What is transduction?

Answer 27

transfer by viral delivery

Question 28

What is conjugation?

Answer 28

plasma transfer

Question 29

Inactivation of drug example

Answer 29

penicillin by beta-lactamase, an enzyme that cleaves a portion of the molecule and renders it inactive

Question 30

decreased permeability

Answer 30

receptor that transports the drug is altered, so the drug cannot enter the cell

Question 31

activation of drug pumps

Answer 31

specialized membrane proteins are activated and continually pump the drug out of the cell (efflux pumps)

Question 32

change in drug binding site

Answer 32

binding site on target (ribosome) is altered so drug has no effect

Question 33

use of alternate metabolic pathway

Answer 33

the drug has blocked the usual metabolic pathway so the microbe circumvents it by using an alternate, unblocked pathway that achieves the required outcome