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Microbiology > Lecture 6: Antibacterial Agents > Flashcards

Lecture 6: Antibacterial Agents Flashcards

(71 cards)

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1
Q

What is the germ theory of disease

A

The idea that microorganisms cause disease

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2
Q

Who discovered the first treatment for syphilis and what was it

A

Paul Ehrlich discovered Arsphenamine (Salvarsan)

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3
Q

Discovery of Arsphenamine (Salvarsan) also led to the foundation of the concept of ____

A

Chemotherapy

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4
Q

What was the first widely available antimicrobial

A

Prontosil

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5
Q

What antibiotic was discovered that started the “golden era” of antibiotics and by who

A

Alexander Fleming discovered penicillin

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6
Q

What is an antibiotic

A

Chemical substance that has the capacity to inhibit the growth of or kill bacterial cells

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7
Q

What does antimicrobial mean

A

Refers to agents that act against all types of microorganisms

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8
Q

What does it mean to be narrow spectrum

A

Effective against limited number of bacteria

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9
Q

What does it mean to be broad spectrum

A

Effective against a wider array of bacteria

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10
Q

What are the pros and cons of narrow spectrum agents

A

pros: treats only specific organisms, less resistance developed

Con: only effective if ID of bacterium is known/correct

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11
Q

What are some pros and cons of broad spectrum agents

A

Pro: less need to make ID
Con: increased development of resistance, disruption of normal microbiome

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12
Q

What does bactericidal mean

A

Kills bacteria

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13
Q

What does bacteriostatic mean

A

Inhibits growth of bacteria

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14
Q

Why don;t you want to give bacteriostatic agents to immunocompromised

A

Relying on immune system to make antibiotics and fight infection

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15
Q

What is selective toxicity

A

Target and kill bacterial cells and not host cells

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16
Q

What makes an antibiotic effective

A
  1. Selective toxicity
  2. Soluble in body fluids
  3. Toxicity is not easily altered
  4. Nonallergenic
  5. Stability
  6. Bacterial resistance is not easily acquired
  7. Reasonable cost
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17
Q

What are the 5 classes of antibiotics

A
  1. Inhibition of cell wall synthesis
  2. Disruption of membrane function
  3. Inhibition of protein synthesis
  4. Inhibition of nucleic acid synthesis
  5. Action as antimetabolites
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18
Q

How is peptidoglycan synthesized

A
  1. NAG and NAM subunits synthesized in cytoplasm
  2. NAG-NAM transported across cell membrane into periplasm
  3. AA side chains cross linked by transpeptidase
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19
Q

What are the 3 classes of cell wall synthesis inhibitors

A
  1. Beta-lactams
  2. Vancomycin
  3. Bacitracin
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20
Q

Are cell wall synthesis inhibitors bactericidal or bacteriostatic

A

Bactericidal

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21
Q

What is the most effective and most extensively used class of antibiotics

A

Cell wall synthesis inhibitors

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22
Q

What is the Beta-lactam ring

A

Active site of antibiotic

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23
Q

What are some notable examples of B-lactam antibiotics

A

Penicillin and cephalosporins

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24
Q

What bacteria does Beta-lactam target

A

Gram positive and negative

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25
What is the mode of action of Beta-lactams
Binds and blocks activity of transpeptidase, preventing cross linking of peptidoglycan layers- resulting in loss of regulation of osmotic pressure- burst and die
26
Which generation of cephalosporins has highest activity against gram positives
First generation
27
What generation of cephalosporins have increasing coverage for gram negatives
Generations 2-5
28
What type of antibiotic is vancomycin
Glycopeptide antibiotic
29
What is vancomycin effective in tx? Narrow or broad spectrum
Narrow spectrum- mainly tx MRSA
30
What is the mode of action for vancomycin
Binds to end the of pentapeptide chains (D-Ala-D-Ala) on NAM blocking transglycosylation and transpeptidation steps of peptidoglycan synthesis
31
How is bacitracin administered and why
Topical use only due to toxicity
32
What is bacitracin effective against, narrow or broad spectrum
Narrow spectrum: use for gram positive organisms, especially those causing skin infections
33
What is the mode of action of bacitracin
Prevents dephosphorylation of bactoprenol (lipid carrier) preventing assembly and transport of NAG-NAM
34
What class of antibiotic is polymixin
Disruption of cell membrane
35
What is polymixin effective against, broad or narrow spectrum
Moderate spectrum against gram negative bacteria
36
How is polymixin administered
Topical or ophthalmic due to toxicity
37
What is the mode of action of polymixin
Acts as cationic detergent disrupting the membrane structure
38
What ribosomes subunits are used in protein synthesis for bacteria
30S and 50S
39
What do aminoglycosides target, narrow or broad spectrum
Broad spectrum- most common use is for tx of severe infections cause by aerobic gram negative bacilli
40
What is the mechanism of action against aminoglycosides
Irreversibly bind to the 30S subunit and block the initiation complex, causing misreading of premature release of mRNA from the ribosome. Halts protein synthesis
41
Are aminoglycosides bactericidal or bacteriostatic
Bactericidal
42
What toxicities do aminoglycosides cause
Ototoxic and nephrotoxic in dogs and cats
43
What are tetracyclines effective against, narrow or broad
Broad spectrum against many gram positives and negatives, many atypical pathogens
44
What is the mode of action of tetracyclines
Binds to the 30S subunit to prevent attachment of the aminoacyl-tRNA to the RNA ribosome complex- prevents adding amino acids to peptide chain, halting protein synthesis
45
Is tetracycline bactericidal or bacteriostatic
Bacteriostatic
46
What antibiotic is toxic to human mitochondria causing aplastic anemia and bone marrow suppression? And which animals can it not be used in
Chloramphenicol- can’t be used in food animals
47
What is the mode of action of amphenicols
Binds to the 50S subunit, inhibiting peptidyl transferase- prevents elongation of peptide chain, halting protein synthesis
48
Are amphenicols bactericidal or bacteriostatic
Bacteriostatic
49
What do macrolides tx, narrow or broad spectrum
Narrow spectrum against some gram negatives and mycoplasma
50
What is the mode of action of macrolides
Binds to 50S subunit, blocking the formation of the initiation complex and translocation- prevents elongation, disrupt protein synthesis
51
Are macrolides bactericidal or bacteriostatic
Bacteriostatic
52
What do lincosamides tx,broad or narrow spectrum
Moderate spectrum- gram positive bacteria, anaerobes, some mycoplasms
53
What is the mode of action for lincosamides
Binds the 50S subunit blocking the formation of initiation complex and translocation
54
Is lincosamides bacteriostatic or bactericidal
Both
55
What species is lincosamides toxic in
Rabbits, guinea pigs and hamsters
56
What species are lincosamides contraindicated in
Horses, neonatal animals, oral administration in ruminants
57
What does streptogramins tx, broad or narrow spectrum
Narrow spectrum for gram positive cocci resistant to other antibiotics
58
What is the mode of action of streptogramins
Bind to different sites on the 50S ribosomal subunit, inhibition of protein synthesis at different steps
59
What do quinolones/ fluoroquinoloes tx, broad or narrow spectrum
Broad spectrum used for enteric infections and intracellular pathogens
60
What is the mode of action of quinilones/ fluoroquinolones
Bind to and inhibit DNA gyrase (topoisomerase II) and toposiomerase IV, preventing bacterial DNA from unwinding and duplicating
61
Are quinolones/ fluoroquinolones bactericidal or bacteriostatic
Bactericidal
62
What do rifamycins tx, broad or narrow spectrum
Moderate spectrum used for mycobacterial infections, some gram positive cocci, select gram negative, rhodoccous equin infections
63
What is the mode of action for rifamycins
Inhibits DNA dependent RNA polymerase, prevents transcription of mRNA
64
Are rifamycins bactericidal or bacteriostatic
Bactericidal
65
What does metronidazole tx, broad or narrow specteum
Narrow spectrum mostly anaerobes and protozoans
66
What is the mode of action of metronidazole
Covalently binds DNA, causing DNA. Breaks
67
Is metronidazole bactericidal or bacteriostatic
Bactericidal
68
What do sulfonamides and diaminopyrimidines tx, broad or narrow spectrum
Broad spectrum against a wide array of gram positive and negative
69
What is the mode of action of sulfonamides and diaminopyrimidines
Interferes with folic acid synthesis needed for DNA synthesis Sulfonamides inhibit diphydropteroate synthetase Trimethoprum- inhibits enzyme dihydrofolate reductase
70
What are some pros of antibiotic use
Reduce pain and suffering, weight gain, livestock live longer, prevent zoonotic diseases, prevent containment of potentially large scale epidemics
71
What is the biggest con of antibiotic use
Multi drug resistant pathogens

Microbiology (31 decks)

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