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Microbiology Exam 1 > Antibiotics > Flashcards

Antibiotics Flashcards

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1
Q

What term is used to describe killing or inhibiting the growth of a microorganism without harming host cells?

A

selective toxicity

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2
Q

What is the difference between bacteriostatic vs. bactericidal?

A

bacteriostatic –> inhibit growth (no killing)

bactericidal –> killing

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3
Q

When is bacteriostatic generally used?

A

when host defenses can be counted on

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4
Q

When is bactericidal generally used?

A

during infection is severe or patient is immunocompromised

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5
Q

Combination of two antibiotics with enhanced bactercidal activity when used together is known as what?

A

antibiotic synergism

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6
Q

Combination of antibiotics in which one interferes with the activity of the other is known as what?

A

antibiotic antagonism

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7
Q

Broad-spectrum antibiotics are effective against a large variety of bacteria, what are the advantages and disadvantages?

A

advantage: incr. likelihood of effectiveness against a bacterial infection of unknown etiology
disadvantage: incr. likelihood of disrupting the patients normal microbiota (but minor to more serious consequences)

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8
Q

Narrow-spectrum antibiotics are effective against only a small subset of bacteria, what are the advantages and disadvantages?

A

advantage: avoids disruption of normal microbiota
disadvantage: must have specific disease causing bacteria identified to choose correct antibiotic

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9
Q

True or False. Antibiotics cause resistance

A

FALSE

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10
Q

What causes antibiotic resistance?

A

general mutation and/ or acquisition of genetic elements from other bacteria carrying resistance genes

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11
Q

What are the three types of antibiotic resistance?

A

1) sensitive
2) intermediate
3) resistant

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12
Q

What type of antibiotic resistance could be treated with a recommended dosage regimen of an antimicrobial agent?

A

sensitive

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13
Q

What type of antibiotic resistance could be treated in body sites where the drug are physiologically concentrated or when a high dosage of drug can be used?

A

intermediate

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14
Q

What type of antibiotic resistance is not usually inhibited by the usually achieved concentrations of the antimicrobial?

A

resistant

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15
Q

When is empiric therapy used?

A

antibiotic treatment while waiting for lab results

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16
Q

When is targeted therapy used?

A

once lab results have been received and bacteria have been identified

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17
Q

What are some general mechanisms in which bacteria can become antibiotic resistant (5)?

A

1) breakdown of an antibiotic (hydrolysis)
2) chemical modification of an antibiotic
3) alteration of the target
4) altered permeability, decreased influx or increased efflux
5) lack of target

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18
Q

What are the two types of activity used in antibiotic susceptibility testing?

A

1) bacteriostatic

2) bactericidal

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19
Q

What is minimum inhibitory concentration (MIC)?

A

lowest concentration of antibiotic that inhibits growth

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20
Q

What is minimum bactericidal concentration (MBC)?

A

lowest concentration of antibiotic that kills 99.9%

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21
Q

How is MIC determined?

A

1) Kirby-Bauer Test (zone of inhibition seen in disk-diffusion assay)
2) E-test (strip of antibiotics with concentration gradient)

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22
Q

How is MBC determined?

A

broth culture –> check for bacterial growth after overnight incubation

23
Q

What is targeted in cell wall active vs membrane active antibiotics?

A

cell wall active –> disrupts peptidoglycan synthesis

membrane active –> disrupts or interferes with membrane integrity/synthesis

24
Q

True or False. Cell wall active antibiotics are effective against resting and actively dividing bacteria

A

FALSE. only effective against actively dividing bacteria. it targets the making of PG, if the bacterium is already there, the antibiotics are not effective against it

25
Q

True of False. Membrane active antibiotics are effective against resting bacteria only

A

FALSE. they are effective against both resting AND actively dividing bacteria

26
Q

Are beta-lactams bactericidal or bacteriostatic?

A

bactericidal

27
Q

What is the mechanism of action of beta-lactams?

A

they inhibit cell wall synthesis, specifically they block the active site of transpeptidase

28
Q

Penicillin is an example of which type of antibiotics?

A

beta-lactams

29
Q

What are some ways bacteria become resistant to beta-lactams (4)?

A

1) altered transpeptidases
2) altered outer-membrane permeability
3) presence of efflux pumps
4) chemical modification of antibiotic

30
Q

When beta-lactams can no longer bind to the active site of transpeptidase, what kind of resistance have the bacteria undergo?

A

altered transpeptidases

31
Q

How does altered outer membrane permeability lead to beta-lactam resistance?

A

protein channels called porins gain mutations that can cause beta-lactams to no longer gain entrance inside the cell

32
Q

How does the presence of efflux pumps lead to beta-lactam resistance?

A

the antibiotics are pumped back out and that effectively reduces the antibiotic concentration within the cell

33
Q

What’s an example of chemical modification of antibiotic that lead to its resistance?

A

the bacteria may have beta-lactamase, an enzyme that turns beta-lactams into its inactive form

34
Q

What is the mechanism of vancomycin?

A

it recognizes and binds to the 2 D-ala on the end of peptide chains thus preventing transpeptidase from interacting. cross-links can’t be formed = cell death

35
Q

How can bacteria become resistant to vancomycin?

A

last D-ala residue has been replaced by a D-lactate and vancomycin can no longer bind to it. cross-links are once again successfully formed and so does cell wall

36
Q

What antibiotics interferes with dephoshorylation in cyclin of lipid carrier, bactoprenol?

A

bacitracin

37
Q

What antibiotics targets protein synthesis?

A

1) tetracyclines
2) aminoglycosides
3) macrolides

38
Q

Tetracyclines are bactericidal or bacterostatic?

A

bacterostatic

39
Q

Aminoglycosides are bactericidal or bacterostatic?

A

bactercidal

40
Q

Macrolides are bactericidal or bacterostatic?

A

bacteriostatic

41
Q

What ribosome subunit do tetracylines bind to?

A

30s

42
Q

What ribosome subunit do aminoglycosides bind to?

A

30s

43
Q

What ribosome subunit do macrolides bind to?

A

50s

44
Q

Which of the three protein synthesis inhibitors is generally used as an alternative for individuals with penicillin allergy?

A

macrolides

45
Q

Which of the three protein synthesis inhibitors is only effective against aerobic organisms because it is oxygen-dependent?

A

aminoglycosides

46
Q

Which of the three protein synthesis inhibitors is a broad spectrum antibiotics?

A

tetracyclines

47
Q

What are the three nucleic acid synthesis inhibitors?

A

1) quinolones
2) rigampin, rifabutin
3) metronidazole

48
Q

Which of the nucleic acid synthesis inhibitors are bactericidal?

A

all three are bactericidal

49
Q

Which of the nucleic acid synthesis inhibitors inhibits DNA replication, recombination and repair?

A

quinolones

50
Q

Which of the nucleic acid synthesis inhibitors binds to DNA-dependent RNA polymerase and inhibits initiation of RNA synthesis?

A

rifampin, rifabutin

51
Q

Which of the nucleic acid synthesis inhibitors gets reduced bacteria and becomes toxic that damages their DNA?

A

metronidazole

52
Q

What type of antibiotics is sulfonamides and trimethoprim?

A

antimetabolites

53
Q

What is the mode of action for sulfonamides and trimethoprim?

A

they target folate metabolism thus preventing bacteria from having the necessary material to build DNA and RNA

Microbiology Exam 1 (10 decks)

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