Exam 1 - (3) Antibiotics

Question 1

Who discovered Penecillin in 1920?

Answer 1

Alexander Fleming

Question 2

What WWII heroes (1940) demonstrated the safety and effectiveness of penicillins in humans?

Answer 2

-Ernst Chain, Howard Flory

Question 3

What are the two modes of antibiotic action?

Answer 3

• Bactericidal

- Bacteriostatic

Question 4

What is the difference between bactericidal and bacteriostatic antibiotics?

Answer 4

-Bacteriostatic slow down bacterial replication/halt growth, bactericidal kill bacteria.

Question 5

What are some qualifications of the “ideal” antibiotic?

Answer 5

• Broad spectrum of activity
• Would not induce bacterial resistance
• High therapeutic index (highly potent but non-toxic to patient; therapeutic index is toxic dose:effective dose)
• Selective toxicity (specific microbes targeted, not host cells)

Question 6

What are some ways an antibiotic achieves selective toxicity?

Answer 6

Targets structures that are unique in microbes:

• cell wall
• enzymes (replication, transcription, translation)
• metabolities
• Ribosome structure

Question 7

What are the five ways antibiotics inhibit bacteria?

Answer 7

1- Inhibition of cell wall synthesis
2-Disruption of cell wall function
3-Inhibition of protein synthesis
4-Inhibition od nucleic acid synthesis
5-Action as antimetabolites

Question 8

What are some examples of antibiotic cell wall synthesis inhibition?

Answer 8

• prevent NAG-NAM binding in the cytoplasm
• prevent peptide side chain binding
• prevent linking of side chain units
• prevents cross-linking of chains

Question 9

Penecillin disrupts cell wall synthesis, how?

Answer 9

-causes competition for bacterial enzyme that cleaves D-ala - D-ala linkage in cell wall synthesis, enzyme instead cleaves penicillin creating toxic fragments.

Question 10

What do generations of antibiotics related to penicillin have in common?

Answer 10

a beta-Lactam ring within their structure

Question 11

Polymyxin B sulfate is an example of an antibiotic which operates by disrupting bacterial cell membranes, how?

Answer 11

It binds to membrane phospholipids.

-note: Polymyxin B sulfate is toxic to eukaryotic cell membranes as well, and as a result is applied topically.

Question 12

Antibiotics that operate by inhibiting protein synthesis act on which bacterial cycle/structure

Answer 12

Ribosome (which is “different” than eukaryotic ribosome)

Question 13

What are some antibiotics that disrupt the bacterial ribosomal cycle?

Answer 13

• Linezolid
• Tetracycline
• Aminoglycosides
• Macrolidies, choramphenicol

Question 14

One mode of antibiotic action is inhibition of nucleic acid synthesis. However, many inhibitors bind to ______ and are thus too ______ for use.

Answer 14

• DNA

- toxic

Question 15

Metronidazole is an exception to the toxic DNA binding inhibitors. This is because it is ______ until it is converted to it’s ______ form by ______ microbes. Therefore it is only active in ^this type^ of bacteria.

Answer 15

• inert
• active
• anerobic

Question 16

Nalidixic acid and Quinolones are examples of antibiotics that affect which bacterial replication structure?

Answer 16

DNA gyrase

Question 17

Rifamycin is an antibiotic that inhibits which bacterial replication structure?

Answer 17

RNA polymerase

Question 18

Para-aminobenzoic acid (PABA) and Para-aminosialic acid are bacteriostatic antibiotics which operate as:

Answer 18

Antimetabolites

Question 19

A result of antibiotic overuse (Agricultural use, Physician misuse, Pharmacist misuse, patient misuse) is:

Answer 19

antibiotic resistance within the bacteria they target.

Question 20

What are the three steps in the action of antibiotics on which drug resistance can act?

Answer 20

1- Drug penetrates the envelope
2-Transport into the cell
3-Drug binds to the target

Question 21

What are three mechanisms of drug resistance?

Answer 21

1-Synthesis of enzymes that inactivate the drug
2-Prevention of access to the target site
-Inhibiting uptake
-Increasing secretion of the drug
3-Modification of the target site

Question 22

Penicillin is deactivated by resistant bacteria by:

Answer 22

synthesizing enzymes which break a bond in penicillin’s b-lactam ring

Question 23

Drug resistant bacteria can prevent the uptake of antibiotics by

Answer 23

• blocking porins to the antibiotics

- creating drug efflux pumps to pump antibiotics out of them (all classes of bacteria have these to some degree)

Question 24

Bacteria can render antibiotics useless by modifying their target sites. Two ways of accomplishing this are:

Answer 24

• Modifying enzyme activity (e.g. developing a higher affinity for a molecule other than the antibiotic)
• Altering their metabolic pathways

Question 25

Name three ways antibiotic resistance spreads:

Answer 25

1-Chromasome associated resistance
2-Plasmid mediated resistance
3-Rapid spread of resistance

Question 26

Bacterial sensitivity to antibiotics occurs over a ______ range.

Answer 26

Dynamic (the few bacteria that are resistant to the antibiotic will eventually thrive and can spread)

Question 27

How do you combat an antibiotic resistant pathogen?

Answer 27

• Synergism - penecillin and streptomycin
• Antagonism - chloramphenicol and penecillin
• Indifference

Question 28

What are drawbacks to administering an antibiotic cocktail?

Answer 28

• Failure to eliminate pathogen (increased likelihood of superinfection)
• Synergistic Toxicity

Question 29

Are antibiotics effective against all microbes?

Answer 29

NO!!!! (fungi, viruses)