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Microbiology > Ch 3: Antimicrobial Agents > Flashcards

Ch 3: Antimicrobial Agents Flashcards

(75 cards)

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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
Which of these microbes is resistant to Carbapenems? A) Enterococcus faceium B) Stenotrophomonas maltophilia C) Burkholderia cepacia D) All of the above
D) all of the above
26
Which microbes are resistant to Carbapenems?
- Methicillin resistant S. aureus - Methicillin resistant S. epidermis - E. faecium - S. maltophilia - B. cepacia
27
What is the mode of action of glycopeptides?
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
28
Which of the following is a Glycopeptide? A) Vancomycin B) Penicillin C) Monobactam D) Erythromycin
A) Vancomycin
29
ToF: Glycopeptides can affect ONLY gram positive bacteria
T: they cannot cross the outer membrane of Gram negatives
30
ToF: Vancomycin is used as a ‘last resort’ drug in medicine
T: due to serious side effects
31
Glycopeptides are bactericidal, except for ______
Enterococcus
32
What is the mode of action of Macrolides?
Inhibit translocation by binding to 50S ribosomal subunit =Bacteriostatic
33
What are examples of Macrolides?
Erythromycin, Clarithromycin, Azithromycin
34
Spectrum of activity of Macrolides
gram positive bacteria, Mycoplasma, Legionella
35
What is Chloramphenicol and Lincosamides mode of action?
Bind to the 50S ribosome and inhibit peptidyl transferase activity
36
ToF:Chloramphenicol has a broad range spectrum of activity
T
37
ToF: Lincomycin and Clindamycin have a broad range spectrum of activity
F: moderate spectrum, primarily active against gram positive bacteria, most anaerobic bacteria and some mycoplasma
38
ToF: Lincomycin and Clindamycin are effective against gram positive bacteria
T
39
When is Chloramphenicol used? What are the adverse effects?
Used for treatment of meningitis (life threatening) It is toxic, causes rare anemia, and liver enzyme inhibition
40
Which of the following is an Aminoglycoside? A) Tobramycin B) Lincomycin C) Erythromycin D) Clarithromycin
A) Tobramycin
41
What are examples of Aminoglycosides?
Gentamicin, Tobramycin, Amikacin
42
What is the mode of action of Aminoglycosides?
Bind to the 30S subunit of ribosomes and inhibit transpeptidation and translocation processes resulting in premature detachment of incomplete polypeptides chains (bactericidal)
43
What is the spectrum of action of Aminoglycosides?
Excellent gram negative, moderate gram positive
44
What are examples of tetracylines?
Minocycline and Doxycycline
45
What is the mode of action of Tetracyclines?
Reversibly bind to 30S ribosome and inhibit binding of aminoacyl-t-RNA to the acceptor site on the 70S ribosome
46
ToF: Tetracyclines have a broad spectrum of activity
T: useful against intracellular bacteria
47
ToF: Tetracyclines have a broad spectrum of activity
T: useful against intracellular bacteria
48
What are the adverse effects of Tetracyclines?
- Destruction of the normal intestinal flora resulting in increased secondary infections - Staining and impairment of the structure of bone and teeth
49
What is the mode of action and spectrum of activity of Streptogramins?
Irreversibly bind to the 50S ribosomal subunit Narrow spectrum
50
_____ is an example of a Streptogramin
Virginiamycin (banned in the EU)
51
What is the mode of action of Oxazolididones?
Protein synthesis inhibitor on the ribosomal 50S subunit of the bacteria; blocks initiation
52
ToF: Linezolid is an Oxazolididone
T: useful for methicillin-resistant S. aureus, Vancomycin-resistant enterococci, and penicillin-resistant S. pneumoniae
53
ToF: Fluoroquinolones function by inhibiting nucleic acid synthesis
T: mode of action = bind to two essential enzymes required for DNA replication (DNA gyrase and topoisomerase IV)
54
Name examples of Fluoroquinolones
Nalidixic acid, ciprofloxacin, ofloxacin, levofloaxcin, sparfloxacin, norfloxacin, moxifloxacin
55
What is the spectrum of activity of Fluoroquinolones?
Gram positive cocci and urinary tract infections
56
What is the spectrum of activity for Ansamycins?
Treatment of tuberculosis and meningitis prophylaxis
57
ToF: Ansamycins do not have any serious adverse effects
F: the most serious adverse effect is hepatotoxicity
58
Name an example of an Ansamycin
Rifampin/Rifampicin
59
What is the mode of action of Ansamycins?
Enters neutrophils and macrophages and inhibits DNA-dependent RNA polymerases
60
ToF: Metronidazol works by inhibiting the production of the cell wall
F: works through inhibition of nucleic acid synthesis; reduce a nitro group in the molecule producing cytotoxic compounds which interfered with bacterial DNA
61
What type of treatment is Metronidazol used for?
Effective against anaerobic bacterial infections (periodontal infections)
62
What type of treatment is Metronidazol used for?
Effective against anaerobic bacterial infections (periodontal infections)
63
ToF: Metronidazol is active against aerobic or facultative bacteria
F: only anaerobic bacteria
64
What is the mode of action for Sulfonamides and Trimethoprim?
Sulfoamides competitively inhibit formation of dihydropteroic acid. Trimetoprim binds to dihydrofolate reductive and inhibits formation of tetrahydrofolic acid (Folic acid synthesis inhibition)
65
Which enzymes are blocked by Sulfonamides and Trimethoprim
Dihydrofolate synthetase is blocked by Sulfoamides Dihydrofolate reductase is blocked by Trimethoprim These enzymes are needed for folic acid synthesis
66
What is the spectrum of activity of Sulfonamides and Trimethoprim?
Broad range against both gram positive and negative; primarily urinary tract and Nocardia
67
ToF: Sulfonamides are used in combination with trimethoprim to block two steps in folic acid metabolism
T: prevents the emergence of resistant strains
68
ToF: Lipopeptides disrupt multiple aspects of bacterial cell membrane function
T
69
Which of the following is an example of a Lipopeptide? A) Erythromycin B) Daptomycin C) Trimethoprim D) Rifampin
B) Daptomycin
70
What is the range of spectrum of Lipopeptides?
Gram positive organisms
71
What is the mode of action of Polymyxins?
Binds to the lipid A portion of lipopolysaccharides and also to phospholipids, disrupting the outer membrane of gram negative
72
ToF: The spectrum of action of Polymyxins is gram negative
T: cell membrane is not exposed in gram positive
73
What is the main goal of combination therapy?
To prevent the emergence of resistance (Also: to treat poly microbial infections)
74
Why do we not use combination therapy all the time?
Antagonism, cost, increased risk of side effects, may enhance resistance, drugs interaction of different classes and often is unnecessary
75
What influences the choice of antibiotics?
- 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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