Bailey Study Guide Antibiotics

Question 1

In 1920, ___ described the potential usefulness of penicillin

Answer 1

alexander fleming

Question 2

What are the different modes of action that antibiotics can have.

Answer 2

• bactericidal

- bacteriostatic

Question 3

___ agents kill bacteria, while ___ agents inhibit growth

Answer 3

bactericidal

bacteriostatic

Question 4

___ and other beta-lactams are antibiotics that affect the cell wall. They are bactericidal.

Answer 4

penicillins

Question 5

Describe the ideal antibiotic

Answer 5

• broad spectrum of activity
• would not induce resistance
• high therapeutic index (ratio between toxic does and effective does; if ratio is 1 then you need a toxic dose in order to eradicate the microbe)
• selective toxicity

Question 6

How is selective toxicity achieved?

Answer 6

• cell wall is unique in microbes
• enzymes for replication, transcription, and translation can be unique in microbes
• microbes have some unique essential metabolites
• ribosome structure unique in microbes

Question 7

What are the 5 ways that antibiotics inhibit bacteria?

Answer 7

1. inhibition of cell wall synthesis
2. disruption of cell membrane function
3. inhibition of protein synthesis
4. inhibition of nucleic acid synthesis
5. action as antimetabolites

Question 8

Antibiotics often work by targeting bacterial ___.

Answer 8

ribosomes

Question 9

There are 2 subunits to bacterial ribosomes, the ___ and ___

Answer 9

30s

50s

Question 10

The ___ subunit is primarily responsible for translation of mRNA

Answer 10

30s

Question 11

The ___ subunit is primarily responsible for joining amino acids together and moving the complex along the mRNA molecule

Answer 11

50s

Question 12

___ and ___ inhibit folic acid metabolism

Answer 12

sulfonamides and trimethoprim

Question 13

How does penicillin disrupt cell wasll synthesis?

Answer 13

1. competition for enzyme that cleaves terminal D-ala

2. When enzyme cleaves, the penicillin is toxic to the bacterial cell

Question 14

All penicillins have ___

Answer 14

B-lactose rings

Question 15

Polymyxin B sulfate disrupts the cell membrane by binding to ___.

Answer 15

phospolipids

Question 16

Aminoglycosides (streptomycin, kanamycin, etc) tetracyclines and erythromycin inhibit ____

Answer 16

protein synthesis

Question 17

___ inhibits DNA sythesis

Answer 17

metronidazole

Question 18

___ intracellular parasites can only grow inside host cells

Answer 18

obligate

Question 19

The ___ is the ratio between the ratio between the effective and toxic dose of an antibiotic

Answer 19

therapeutic index

Question 20

What are some of the commonly used antibiotics in dentistry?

Answer 20

penicillin- odontogenic infections
clindamycin- odontogenic infections (bone), abscesses
cephalosporins- odontogenic infections
metronidazole- abscesses and periodontitis
tetracyclines- periodontitis

Question 21

The ___ drugs interact with an enzyme to prevent the production of a metabolite.

Answer 21

sulfa

Question 22

Steps in the action of antibiotics

Answer 22

1. drug penetrates the envelope
2. transport into the cell
3. drug binds to target
   (resistance to drugs occurs at each of these steps)

Question 23

Mechanisms of drug resistance

Answer 23

1. synthesis of enzymes that inactives the drug
2. prevention of access to the target site
   - inhibiting uptake
   - increasing secretion of the drug
3. modification of the target site
   - modify enzyme affinity
   - alteration of metabolic pathway

Question 24

How does antibiotic resistance spread?

Answer 24

1. chromosome associated resistance
2. plasmid mediated resistance
3. rapid spread of resistance

Question 25

How do you combat an antibiotic resistant pathogen?

Answer 25

- synergism: ex) penicillin and streptomycin - antagonism: ex) chloramphenicol and penicillin - indifference ex) many antibiotics are "indifferent"

Question 26

Are there drawbacks to administering an antibiotic cocktail?

Answer 26

- failure to eliminate the pathogen: increased likelihood of superinfection - synergistic toxicity

Question 27

Are antibiotics effective against all microbes?

Answer 27

no. viruses, fungi, and a few bacteria

Question 28

Many structures on the microbial surface consist of repeated molecules referred to as ___.

Answer 28

pathogen associated molecular patterns

Question 29

Drug resistant genes are often found on ___ that can be transferred readily from one bacteria to another.

Answer 29

plasmids

Question 30

Bacteria are often classified via their ___.

Answer 30

surface antigens (in this scheme, O refers to LPS, H refers to flagella, and K refers to a capsule)