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Microbiology > Ch 3: Antimicrobial Agents > Flashcards

Ch 3: Antimicrobial Agents Flashcards

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Biology 101 flashcards
1
Q

What is differential toxicity?

A

Drugs are more toxic to infecting organism than to the host

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2
Q

What are some traits of the ideal antimicrobial?

A
  • *appropriate spectrum of activity for the clinical setting
  • *no toxicity to host, be well tolerated
  • wont develop resistance
  • wont induce hypersensitivities
  • long half life
  • rapid and extensive tissue distribution
  • easy to administer
  • inexpensive
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3
Q

Who developed the idea of selective toxicity?

A

Paul Ehrich

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4
Q

Who discovered that Penicillium notatum, a common mold, had destroyed staphylococcus bacteria in culture, discovering penicillin?

A

Sir Alexander Fleming

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5
Q

What is minimum inhibitory concentration (MIC)?

A

Minimum concentration of antibiotics required to inhibit the growth of test organism

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6
Q

What is minimum bactericidal concentration (MBC)?

A

Minimum concentration of antibiotic required to kill the test organism

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7
Q

What is the difference between treatment and prophylaxis?

A

Prophylaxis is when antimicrobials are used (usually in life threatening infections) to prevent infection, while treatment are used to cure existing infections

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8
Q

Which one is NOT a beta lactam?
A) penicillin
B) monobactams
C) carbapenems
D) teicoplanin

A

D) teicoplanin

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9
Q

ToF: Penicillins are strong inhibitors of Gram negative organisms

A

F: act on bacterial cell walls especially in Gram positive organisms

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10
Q

ToF: Penicillins are toxic to animal cells

A

F: not toxic, only work on organisms with a cell wall

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11
Q

Beta lactams are produced by:
A) fungi
B) ascomycetes
C) actinomycetes
D) all of the above

A

D) all of the above

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12
Q

What is the mode of action of penicillins?

A

beta lactam ring binds to penicillin binding protein (PBP) and PBP is unable to cross link peptidoglycan chains. Consequently, bacteria is unable to synthesize a stable cell wall, bacteria is lysed

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13
Q

Which of these would be effective against Staphylococcus?
A) Penicillin G
B) Synthetic penicillins
C) Cloxacillin
D) Piperacillin

A

C) Cloxacillin

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14
Q

Which of the following would be effective against Pseudomonas?
A) Piperacillin
B) Penicillin V
C) Methicillin
D) Cloxacillin

A

A) Piperacillin

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15
Q

ToF: Pencillin G/V is effective against gram negative bacteria.

A

F: not effective against gram negatives or anaerobic bacteria

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16
Q

What compounds are prescribed along beta lactamic antibiotics?

A

Clavulanic acid, sulbactam, or tazobactam. These are beta lactamase inhibitors

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17
Q

What is the mode of action of Cephalosporins

A

Inhibit PBP (penicillin binding protein) and therefore cannot make cross links, unstable cell wall and cell lyses

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18
Q

How are Cephalosporins different to penicillin?

A

They have wider antibacterial spectrum, resistant to many beta-lactameses and have longer half lives

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19
Q

What generation of Cephalosporins is Ceftriaxone?

A

3rd: excellent gram negative, some gram positive

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20
Q

What is the name and generation of the Cephalosporins with excellent effectiveness with gram negative, and good gram positive bacteria?

A

4th generation, Cefepime

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21
Q

Which generation of Cephalosporins does Cefazolin belong to?

A

1st (mainly gram positive, some gram negative)

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22
Q

Which generation of Cephalosporins does Cefuroxime belong to?

A

2nd (weaker gram positive, better gram negative)

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23
Q

ToF: Monobactams have a broad spectrum of activity

A

F: narrow spectrum

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24
Q

Which beta-lactam has the most broad spectrum of activity of all antimicrobials?

A

Carbapenems

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25
Q

Which of these microbes is resistant to Carbapenems?
A) Enterococcus faceium
B) Stenotrophomonas maltophilia
C) Burkholderia cepacia
D) All of the above

A

D) all of the above

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26
Q

Which microbes are resistant to Carbapenems?

A
  • Methicillin resistant S. aureus
  • Methicillin resistant S. epidermis
  • E. faecium
  • S. maltophilia
  • B. cepacia
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27
Q

What is the mode of action of glycopeptides?

A

Inhibit bacterial cell wall synthesis by binding to the D-alanine-D-alanine termini of the chain
Interfere with the formation of bridges between the peptidoglycan chains

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28
Q

Which of the following is a Glycopeptide?
A) Vancomycin
B) Penicillin
C) Monobactam
D) Erythromycin

A

A) Vancomycin

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29
Q

ToF: Glycopeptides can affect ONLY gram positive bacteria

A

T: they cannot cross the outer membrane of Gram negatives

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30
Q

ToF: Vancomycin is used as a ‘last resort’ drug in medicine

A

T: due to serious side effects

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31
Q

Glycopeptides are bactericidal, except for ______

A

Enterococcus

32
Q

What is the mode of action of Macrolides?

A

Inhibit translocation by binding to 50S ribosomal subunit
=Bacteriostatic

33
Q

What are examples of Macrolides?

A

Erythromycin, Clarithromycin, Azithromycin

34
Q

Spectrum of activity of Macrolides

A

gram positive bacteria, Mycoplasma, Legionella

35
Q

What is Chloramphenicol and Lincosamides mode of action?

A

Bind to the 50S ribosome and inhibit peptidyl transferase activity

36
Q

ToF:Chloramphenicol has a broad range spectrum of activity

A

T

37
Q

ToF: Lincomycin and Clindamycin have a broad range spectrum of activity

A

F: moderate spectrum, primarily active against gram positive bacteria, most anaerobic bacteria and some mycoplasma

38
Q

ToF: Lincomycin and Clindamycin are effective against gram positive bacteria

A

T

39
Q

When is Chloramphenicol used? What are the adverse effects?

A

Used for treatment of meningitis (life threatening)
It is toxic, causes rare anemia, and liver enzyme inhibition

40
Q

Which of the following is an Aminoglycoside?
A) Tobramycin
B) Lincomycin
C) Erythromycin
D) Clarithromycin

A

A) Tobramycin

41
Q

What are examples of Aminoglycosides?

A

Gentamicin, Tobramycin, Amikacin

42
Q

What is the mode of action of Aminoglycosides?

A

Bind to the 30S subunit of ribosomes and inhibit transpeptidation and translocation processes resulting in premature detachment of incomplete polypeptides chains (bactericidal)

43
Q

What is the spectrum of action of Aminoglycosides?

A

Excellent gram negative, moderate gram positive

44
Q

What are examples of tetracylines?

A

Minocycline and Doxycycline

45
Q

What is the mode of action of Tetracyclines?

A

Reversibly bind to 30S ribosome and inhibit binding of aminoacyl-t-RNA to the acceptor site on the 70S ribosome

46
Q

ToF: Tetracyclines have a broad spectrum of activity

A

T: useful against intracellular bacteria

47
Q

ToF: Tetracyclines have a broad spectrum of activity

A

T: useful against intracellular bacteria

48
Q

What are the adverse effects of Tetracyclines?

A
  • Destruction of the normal intestinal flora resulting in increased secondary infections
  • Staining and impairment of the structure of bone and teeth
49
Q

What is the mode of action and spectrum of activity of Streptogramins?

A

Irreversibly bind to the 50S ribosomal subunit
Narrow spectrum

50
Q

_____ is an example of a Streptogramin

A

Virginiamycin (banned in the EU)

51
Q

What is the mode of action of Oxazolididones?

A

Protein synthesis inhibitor on the ribosomal 50S subunit of the bacteria; blocks initiation

52
Q

ToF: Linezolid is an Oxazolididone

A

T: useful for methicillin-resistant S. aureus, Vancomycin-resistant enterococci, and penicillin-resistant S. pneumoniae

53
Q

ToF: Fluoroquinolones function by inhibiting nucleic acid synthesis

A

T: mode of action = bind to two essential enzymes required for DNA replication (DNA gyrase and topoisomerase IV)

54
Q

Name examples of Fluoroquinolones

A

Nalidixic acid, ciprofloxacin, ofloxacin, levofloaxcin, sparfloxacin, norfloxacin, moxifloxacin

55
Q

What is the spectrum of activity of Fluoroquinolones?

A

Gram positive cocci and urinary tract infections

56
Q

What is the spectrum of activity for Ansamycins?

A

Treatment of tuberculosis and meningitis prophylaxis

57
Q

ToF: Ansamycins do not have any serious adverse effects

A

F: the most serious adverse effect is hepatotoxicity

58
Q

Name an example of an Ansamycin

A

Rifampin/Rifampicin

59
Q

What is the mode of action of Ansamycins?

A

Enters neutrophils and macrophages and inhibits DNA-dependent RNA polymerases

60
Q

ToF: Metronidazol works by inhibiting the production of the cell wall

A

F: works through inhibition of nucleic acid synthesis; reduce a nitro group in the molecule producing cytotoxic compounds which interfered with bacterial DNA

61
Q

What type of treatment is Metronidazol used for?

A

Effective against anaerobic bacterial infections (periodontal infections)

62
Q

What type of treatment is Metronidazol used for?

A

Effective against anaerobic bacterial infections (periodontal infections)

63
Q

ToF: Metronidazol is active against aerobic or facultative bacteria

A

F: only anaerobic bacteria

64
Q

What is the mode of action for Sulfonamides and Trimethoprim?

A

Sulfoamides competitively inhibit formation of dihydropteroic acid.
Trimetoprim binds to dihydrofolate reductive and inhibits formation of tetrahydrofolic acid
(Folic acid synthesis inhibition)

65
Q

Which enzymes are blocked by Sulfonamides and Trimethoprim

A

Dihydrofolate synthetase is blocked by Sulfoamides
Dihydrofolate reductase is blocked by Trimethoprim
These enzymes are needed for folic acid synthesis

66
Q

What is the spectrum of activity of Sulfonamides and Trimethoprim?

A

Broad range against both gram positive and negative; primarily urinary tract and Nocardia

67
Q

ToF: Sulfonamides are used in combination with trimethoprim to block two steps in folic acid metabolism

A

T: prevents the emergence of resistant strains

68
Q

ToF: Lipopeptides disrupt multiple aspects of bacterial cell membrane function

A

T

69
Q

Which of the following is an example of a Lipopeptide?
A) Erythromycin
B) Daptomycin
C) Trimethoprim
D) Rifampin

A

B) Daptomycin

70
Q

What is the range of spectrum of Lipopeptides?

A

Gram positive organisms

71
Q

What is the mode of action of Polymyxins?

A

Binds to the lipid A portion of lipopolysaccharides and also to phospholipids, disrupting the outer membrane of gram negative

72
Q

ToF: The spectrum of action of Polymyxins is gram negative

A

T: cell membrane is not exposed in gram positive

73
Q

What is the main goal of combination therapy?

A

To prevent the emergence of resistance
(Also: to treat poly microbial infections)

74
Q

Why do we not use combination therapy all the time?

A

Antagonism, cost, increased risk of side effects, may enhance resistance, drugs interaction of different classes and often is unnecessary

75
Q

What influences the choice of antibiotics?

A
  • activity of agent against proven or suspected organism
  • site of infection
  • mode of administration
  • metabolism and excretion
  • duration of treatment, frequency of dose
  • toxicity/ cost
  • local rates of resistance

Microbiology (3 decks)

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