EXAM #4: INTRODUCTION TO ANTIBACTERIAL AGENTS

Question 1

What shape are streptococci?

Answer 1

Chains

Question 2

What shape are staphylococci?

Answer 2

Grape-like clusters

Question 3

What shape are pleomorphic bacteria?

Answer 3

Many-shapes

Question 4

What molecule is the foundation of the bacterial cell wall?

Answer 4

Peptidoglycan

Question 5

What is peptidoglycan?

Answer 5

Macromolecule of:

• Peptides
• Sugars

Question 6

In regards to peptidoglycan, what is the difference between gram positive and gram negative bacteria?

Answer 6

Gram positive= thick wall of peptidoglycan

Gram negative= thin wall of peptidoglycan
- PLUS an OUTER MEMBRANE

Question 7

What is LPS?

Answer 7

Lipopolysaccharide

Question 8

What is lipopolysaccharide?

Answer 8

Macromolecule of:

• Phospholipids
• Polysaccharides

Question 9

What type of bacteria is LPS associated with?

Answer 9

Gram negative

Question 10

What is the effect of LPS from a therapeutic standpoint?

Answer 10

Prevents penetration of the organism by bulky/ high molecular weight drugs

E.g. erythromycin

Question 11

What effect does the lipid bilayer in Gram negative bacteria from a therapeutic standpoint?

Answer 11

Prevents penetration by water-soluble drugs

Question 12

What is the effect of hydrophillic pores in Gram negative bacteria?

Answer 12

Allows penetration by water soluble drugs

E.g. sulfonamides

Question 13

What is the role of nutrient receptors in Gram negative therapy?

Answer 13

Nutrient receptors can be utilized by structurally similar drugs to gain entry into the organism

Question 14

What type of bacteria is Teichoic acid associated with?

Answer 14

Gram positive

Question 15

What effect does Tiechoic acid have on therapy?

Answer 15

• Anionic

- Can hinder penetration of drugs with a negative charge

Question 16

What effect does the lipid bilayer have on therapy in Gram positive bacteria?

Answer 16

Limits the penetration of water soluble drugs

E.g. sulfonamides

Question 17

What is the definition of selective toxicity?

Answer 17

Therapy aimed at killing only the target organism

- Uses drug targets that are specific to organism

Question 18

What are the common strategies for killing or inhibiting microorganism growth?

Answer 18

1) Disrupt the coding/ genetic machinery
2) Block protein synthesis
3) Disrupt cell wall/ membrane synthesis

Question 19

What is the definition of bactericidal?

Answer 19

Agent will KILL the bacteria

Question 20

What is the definition of bacteriostatic?

Answer 20

Agent will INHIBIT GROWTH of the bacteria

Note that this type of elimination is DEPENDENT on host immune system

Question 21

What is a narrow spectrum abx?

Answer 21

Drug that is TARGETED to a specific species of bacteria

Question 22

What is a broad spectrum abx? When would you employ broad spectrum therapy?

Answer 22

Drug that has an effect on a variety of organisms

Use if the causative agent is unknown

Question 23

What is prophylactic therapy?

Answer 23

• Treatment without disease

- Prevention

Question 24

What is pre-emptive therapy?

Answer 24

• Treatment of a high-risk patient that is infected

- but, ASYMPTOMATIC

Question 25

What is empirical therapy?

Answer 25

Treatment of a SYMPTOMATIC patient without testing/confirmation of the causative organism

Question 26

What is definitive therapy?

Answer 26

Treatment once the causative organism has been identified

Question 27

What is suppressive therapy?

Answer 27

• Low dose therapy used as a “secondary prophylaxis”

- Causative agent is likely still present

Question 28

What is the definition of resistance?

Answer 28

When the agent is no longer effective, OR is less effective against the organism

Question 29

How do bacteria develop drug resistance?

Answer 29

1) Acquisition of NEW genetic material

2) Mutation in the EXISTING genome

Question 30

What mnemonic can be used to remember the “nosocominal superbugs?”

Answer 30

ESKAPE

• Enterococcus faecium
• Staphylococcus aureus
• Klebsiella pneumoniae
• Acinetobacter baumanni
• Pseudomonas aeruginosa
• Enterobacter species

Question 31

What resistance mechanism is associated with Daptomycin?

Answer 31

• Gene mutation (mprF) that changes the CHARGE of the bacterial membrane
• Positive
• Repels positively charged abx i.e. Daptomycin

Generally, this is an example of REDUCED DRUG ENTRY

Question 32

What resistance mechanism of associated with Tetracycline?

Answer 32

• Expression of an EFFLUX PUMP that pumps Tetracycline OUT of the organism
• This is an example of increased DRUG EFFLUX*

Question 33

What resistance mechanism is associated with Metronidazole?

Answer 33

• Metronidazole is a pro-drug
• Must be REDUCED to be ACTIVE
• Bacteria develop mutations that alter the enzymes that activate Metronidazole

Example of changes in enzymes that activate the drug

Question 34

What resistance mechanism is associated with Aminoglycosides?

Answer 34

• Mutations produce enzymes that chemically modify the drug
• Structural changes impair binding to target

Imparied drug binding to targets

Question 35

What resistance mechanism is assocaited with Amoxicillin?

Answer 35

• Expression of Beta-lactamase

- Enzyme hydrolyzes the lactam ring that is part of the amoxicillin structure

Question 36

What is the trade name of Amoxacillin + a Beta-Lactamase inhibitor?

Answer 36

Augmentin

Question 37

What is the resistance mechanism that is associated with TMP-SMX?

Answer 37

• Mutation of the drug binding site

E.g. TMP-SMX targets dihydrofolate reductase–drug binding site is altered but the enzyme still functions

Question 38

What is the mechanism of Vancomycin resistance?

Answer 38

• Vancomycin inhibits cell wall synthesis
• Binds to sites in the growing peptidoglycan wall and sterically inhibits the synthesis of peptidoglycan
• Mutation prevents vanocmycin binding but still allows the formation of the cell wall