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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?

A

Linezolid

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
Q

What is the only antibiotic that can inhibit DNA replication, without being too toxic to use?

A

Metronidazole

- activated by anaerobic microbes

26
Q

Nalidixic acid and Quinolones are antibiotics that affect ____ ____

A

DNA gyrase

27
Q

What antibiotics inhibit RNA polymerase?

A

Rifamycin

28
Q

Sulfa drugs act as a ______ and are _____ antibiotics

A

antimetabolite, bacteriostatic

29
Q

Because of the ____ ____ exerted by antibiotics, bacteria have become antibiotic resistant within one human generation

A

Selective pressure

30
Q

What are the 3 steps in the action of antibiotics?

A
  1. Drug penetrates the envelope
  2. Transport into the cell
  3. Drug binds to target
31
Q

What steps does resistance to drugs occur?

A

All three

32
Q

What are the three mechanisms of drug resistance?

A
  1. Synthesis of enzymes that inactive the drug
  2. Prevention of access to target site
  3. Modification of target site
33
Q

What are the 2 ways that a bacteria can prevent an antibiotic from accessing the target site?

A
  1. inhibit uptake

2. inc secretion of drug

34
Q

B- lactamases do what to penicillin?

A

Destroy B-lactam ring

- imp. to cleave to created toxic compound to bacteria

35
Q

How do antibiotics enter the cell?

A

Porins (extend across lipid bilayer)

- resistance to tetracyclines and quinolones

36
Q

Some bacteria develop ______ to pump the antibiotics out of them

A

efflux pumps (all bacteria have theses, depends on how active they are)

37
Q

How does a microbe modify the target site?

A
  1. Modify enzyme affinity

2. Alteration of Metabolic Pathway

38
Q

How does antibiotic resistance spread?

A
  1. Chromosome associated resistance
  2. Plamid mediated resistance
  3. Rapid spread of resistance
39
Q

What is the main reason it is important to finish the course of an antibiotic?

A

High resistant bacteria take longer time to die, if you stop taking the antibiotic prematurely, then the number of antibiotic resistant bacteria increases

40
Q

How do you combat an antibiotic resistant pathogen?

A
  1. Synergism (2+ antibiotics)
  2. Antagonism
  3. Indifference
41
Q

What are the drawbacks to administering an antibiotic cocktail?

A
  1. Failure to eliminate pathogen ( superinfection)

2. Synergism toxicity

42
Q

Failure to eliminate a pathogen increases the likelihood of _______

A

superinfection

43
Q

Are antibiotics effective against all microbes?

A

No, not effective against viruses, some fungi

Microbio Ex 1 (18 decks)

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