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Microbio Ex 1 > Ex1- Bailey- Effects of Antibiotics on Life Cycle of Bacteria > Flashcards

Ex1- Bailey- Effects of Antibiotics on Life Cycle of Bacteria Flashcards

1
Q

In 1920, Alexander Fleming described the potential usefulness of _____

A

penecillin

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2
Q

In 1940, Ernst Chain and Howard Flory demonstrated the safety and effectiveness of ___ (changed scope of WWII)

A

penicillins in humans

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3
Q

What are the two different modes of action of antibiotics?

A
  • Bactericidal

- Bacteriostatic

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4
Q

What action of antibiotics kills bacteria?

A

Bactericidal

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5
Q

What action of antibiotics prevents bacterial from replicating, slows down bacteria (reduces metabolic activity)

A

Bacteriostatic

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6
Q

_____ antibiotics act more rapidly than ____ antibiotics

A
  • Bacteriocidal

- Bacteriostatic

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7
Q

Tetracycline is an example of ____ antibiotic

A

Bacteriorstatic

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8
Q

Penicillin is an example of a ______ antibiotic

A

bactericidal

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9
Q

An ideal antibiotic has what 4 characteristics?

A
  • Broad spectrum of activity
  • Not induce resistance
  • High therapeutic index
  • Selective Toxicity
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10
Q

The ratio between toxic and effective dose; if the ratio is 1, then you need a toxic dose in order to eradicate the microbe

A

High therapeutic index

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11
Q

Is a high or low therapeutic index wanted in order to not effect host?

A

high bc a low dose is effective to kill bacteria but will not effect host

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12
Q

What are the four things are unique to microbes that help them achieve selective toxicity?

A
  • Cell wall
  • Enzymes for replication, transcription, and translation
  • Essential metabolites
  • Ribosome
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13
Q

What are the 5 ways that antibiotics inhibit bacteria?

A
  1. Inhibition of cell wall synthesis
  2. Disruption of cell membrane function
  3. Inhibition of protein synthesis
  4. Action of metabolites
  5. Inhibition of nucleic acid synthesis
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14
Q

What are some ways that antibiotics inhibit bacteria cell wall synthesis?

A
  • NAG binding NAM
  • prevent peptide side chains from binding NAM
  • prevent Murein cross linking
  • transport of chain to periplasmic space
  • NAG/NAM elongation
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15
Q

How does penicillin disrupt cell wall synthesis?

A
  • prevents Murein cross linking
  • Competition for enzyme that cleaves terminal D-alanine (needed to form peptide bond)
  • Enzyme cleaves penicillin- compound toxic to cell membrane
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16
Q

What in penicillin does the enzyme work on?

A

B- lactam ring

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17
Q

___ ___ ___ disrupts cell membrane function by binding to phospholipids

A

polymyxin B Sulfate

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18
Q

What is targeted in the inhibition of protein synthesis?

A

Bacterial Ribosome (Different structure than eukaryotes)

19
Q

What are some of the places of antibiotic inhibition involving ribosomes?

A
  • 50S and 30S binding
  • prevention of tRNAs to bring AAs to 30S
  • formation of initiation complex
  • prevent elongation of AA chain
20
Q

What antibiotic prevents the formation of the initiation complex of ribosomes?

21
Q

What antibiotic binds to 30S subunit and blocks tRNA from attaching to 30S subunit in the ribosome cycle?

A

Tetracycline

22
Q

What antibiotic blocks elongation but not RNA binding in the ribosome cycle?

A

Aminoglycosides

23
Q

What antibiotic binds to the 50S to inhibit chain elongation causing the ribosome to dissociate from RNA resulting in a truncated ribosome cycle

A

Macrolides chloramphenicol

24
Q

What is an issue with inhibitors of DNA replication?

A

They bind to DNA and are too toxic for use (sim. btw eukaryotes + bacteria)

25
What is the only antibiotic that can inhibit DNA replication, without being too toxic to use?
Metronidazole | - activated by anaerobic microbes
26
Nalidixic acid and Quinolones are antibiotics that affect ____ ____
DNA gyrase
27
What antibiotics inhibit RNA polymerase?
Rifamycin
28
Sulfa drugs act as a ______ and are _____ antibiotics
antimetabolite, bacteriostatic
29
Because of the ____ ____ exerted by antibiotics, bacteria have become antibiotic resistant within one human generation
Selective pressure
30
What are the 3 steps in the action of antibiotics?
1. Drug penetrates the envelope 2. Transport into the cell 3. Drug binds to target
31
What steps does resistance to drugs occur?
All three
32
What are the three mechanisms of drug resistance?
1. Synthesis of enzymes that inactive the drug 2. Prevention of access to target site 3. Modification of target site
33
What are the 2 ways that a bacteria can prevent an antibiotic from accessing the target site?
1. inhibit uptake | 2. inc secretion of drug
34
B- lactamases do what to penicillin?
Destroy B-lactam ring | - imp. to cleave to created toxic compound to bacteria
35
How do antibiotics enter the cell?
Porins (extend across lipid bilayer) | - resistance to tetracyclines and quinolones
36
Some bacteria develop ______ to pump the antibiotics out of them
efflux pumps (all bacteria have theses, depends on how active they are)
37
How does a microbe modify the target site?
1. Modify enzyme affinity | 2. Alteration of Metabolic Pathway
38
How does antibiotic resistance spread?
1. Chromosome associated resistance 2. Plamid mediated resistance 3. Rapid spread of resistance
39
What is the main reason it is important to finish the course of an antibiotic?
High resistant bacteria take longer time to die, if you stop taking the antibiotic prematurely, then the number of antibiotic resistant bacteria increases
40
How do you combat an antibiotic resistant pathogen?
1. Synergism (2+ antibiotics) 2. Antagonism 3. Indifference
41
What are the drawbacks to administering an antibiotic cocktail?
1. Failure to eliminate pathogen ( superinfection) | 2. Synergism toxicity
42
Failure to eliminate a pathogen increases the likelihood of _______
superinfection
43
Are antibiotics effective against all microbes?
No, not effective against viruses, some fungi

Microbio Ex 1 (18 decks)

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