Booklet 6: Antimicrobial Drugs and Resistance

Question 1

List 3 important points about antimicrobial drugs

Answer 1

• They are compounds that kill or control the growth of microorganisms in the host
• Selective toxicity
• Two broad categories: synthetic and natural

Question 2

What are growth factor analogs?

Answer 2

• Structurally similar to growth factors but do not function in the cell
• Analogs similar to vitamins, amino acids, and other compounds

Question 3

Who were sulfa drugs discovered by and when?

Answer 3

Gerhard Domagk in the 1930’s

Question 4

Are sulfa drugs fully synthetic?

Answer 4

Yes

Question 5

How do sulfa drugs work?

Answer 5

-Inhibit growth of bacteria (ex. sulfanilamide) by inhibiting folic acid synthesis and thus nucleic acid synthesis.

Question 6

How do quinolones work?

Answer 6

• They inhibit DNA gyrase (ex. ciprofloxacin) and prevent DNA supercoiling.
• They are active against both Gram-negative and Gram-positive bacteria

Question 7

Are quinolones synthetic or natural?

Answer 7

Synthetic

Question 8

What are natural antimicrobial drugs produced by?

Answer 8

Bacteria and Fungi

Question 9

What percentage of known natural antibiotics are clinically useful?

Answer 9

Less than 1%

Question 10

Antibiotics can be split up into synthetic or natural. They can also be split up into what two categories?

Answer 10

Broad spectrum vs narrow spectrum

Question 11

Explain the difference between broad and narrow spectrum antibiotics.

Answer 11

Broad - targets most bacteria, has no preference for gram positive or gram negative
Narrow - targets specific bacteria, has a preference for either gram positive or gram negative

Question 12

List 2 points about B-lactam antibiotics.

Answer 12

• Cell wall synthesis inhibitors

- Compromise over 50% of antibiotics used around the world.

Question 13

What are 2 popular examples of B-lactam antibiotics?

Answer 13

• Cephalosporins

- Penicillins

Question 14

Describe penicillin antibiotics.

Answer 14

• Discovered by Alexander Fleming

- Target cell wall (specifically peptidoglycan synthesis)

Question 15

Are penicillins effective against gram positive or gram negative bacteria?

Answer 15

Gram positive. (Some synthetic forms are active against gram negative bacteria).

Question 16

What are cephalosporin antibiotics made from?

Answer 16

The fungus: Cephalospyrium sp.

Question 17

Are cephalosporins more broad than penicillins?

Answer 17

Yes (They not only cover gram positives but have some gram negative coverage as well).

Question 18

List 2 points about cephalosporins

Answer 18

• Resistant to B-lactamases

- Commonly used to treat gonorrhoea

Question 19

List 4 types of antibiotics created from bacteria.

Answer 19

• Aminoglycosides
• Macrolides
• Tetracyclines
• Novel Antibiotics

Question 20

Describe aminoglycosides

Answer 20

• Amino sugars bonded by glycosidic linkage
• Examples include: streptomycin, kanamycin, neomycin, gentamicin.
• Target 30S subunit of the ribosome
• Useful against gram-negative bacteria
• Not commonly used, known as “last resort” antibiotics

Question 21

Describe macrolides

Answer 21

• Lactone rings bonded to sugars
• Example: erythromycin (streptomycin erythreus)
• Broad spectrum
• Target 50S subunit of the ribosome (partial inhibition of protein synthesis - preferential translation of some proteins)

Question 22

Describe tetracyclines

Answer 22

• Produced by several species of Streptomycin
• Broad spectrum
• Natural and semisynthetic
• Inhibit 30S subunit of ribosome
• Most widely used antibiotic along with penicillins
• Veterinary and as growth promoters (resistance)

Question 23

List 2 types of novel antibiotics

Answer 23

• Daptomycin

- Platensimycin

Question 24

Describe daptomycin

Answer 24

• Cyclic lipopeptide
• Active against gram positives
• Forms pores in cell membrane (depolarization)

Question 25

Describe platensimycin

Answer 25

• New class of antibiotic
• Fatty acid biosynthesis inhibitor
  - No host toxicity
• Broad spectrum including MRSA and VRE

Question 26

What does MRSA stand for?

Answer 26

methicillin-resistant staph aureus

Question 27

Define: antimicrobial drug resistance

Answer 27

The ability of a microorganism to resist the effects of an antimicrobial agent to which it is normally sensitive

Question 28

What two types of antimicrobial drug resistance are there?

Answer 28

Chromosomal vs plasmid-encoded

Question 29

List some mechanisms of resistance and provide examples

Answer 29

• Reduced permeability - penicillin
• Inactivation of antibiotic - penicillins, chloramphenicol, aminoglycerides
• Alteration of target - erythromycin, streptomycin, norfloxacin
• Development of resistant biochemical pathway
  
  • sulfonamides
• Efflux - tetracyclines, chloramphenicol, fluoroquinolones

Question 30

What creates antibiotic resistance?

Answer 30

Widespread antibiotic usage in medicine, veterinary, and agriculture selects for resistance

Question 31

What % of all antibiotics produced are used for agricultural practises?

Answer 31

80%

Question 32

What does VRE stand for?

Answer 32

vancomycin-resistant enterococci

Question 33

What are the two most commonly known resistant bacteria?

Answer 33

MRSA and VRE

Question 34

List 4 points that would contribute to preventing antimicrobial resistance

Answer 34

• Prevention of infections
• Rapid, conclusive diagnosis
• Prudent use of antimicrobials (not using unnecessarily)
• Prevention of transmission