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UVic BIOL 459 - Fall 2019 > Final > Disease Control: Antimicrobials > Flashcards

Final > Disease Control: Antimicrobials Flashcards

1
Q

What is chemotherapy?

A

The use of chemicals to treat a disease.

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2
Q

What is “selective toxicity” with regards to chemotherapy?

A

Selectively finding and destroying pathogens without damaging the host.

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3
Q

What is an antibiotic?

A

A substance produced by a microbe that, in small amounts, inhibits another microbe.

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4
Q

What is an antimicrobial drug?

A

A synthetic substance that interferes with the growth of microbes.

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5
Q

When was penicillin discovered? When were the first clinical trials?

A

Discovered in 1928. First clinical trials in 1940.

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6
Q

What differentiates narrow-spectrum antibiotics from broad-spectrum antibiotics?

A

It’s literally in the name. Ur dumb if you didn’t get this.

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7
Q

What is a superinfection?

A

Overgrowth of normal microbiota that is resistant to antibiotics.

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8
Q

What is an example of a broad-spectrum antimicrobial drug? What about a narrow-spectrum drug?

A

Broad: Streptomycin, Tetracycline
Narrow: Acyclovir

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9
Q

What differentiates a bactericidal drug from a bacteriostatic drug?

A

Bactericidal: kills microbes
Bacteriostatic: prevents microbes from growing

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10
Q

In what circumstance might a bacteriostatic drug be ineffective?

A

When a person’s immune system is compromised an not capable of killing the microbes, even though their replication is halted.

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11
Q

What are the 5 bacterial sites that are targeted by antibiotics? Give an example of a drug for each if you can.

A
  1. Cell wall (penicillin)
  2. Protein synthesis (tetracycline)
  3. Inhibition of nucleic acids (rifampin for RNA, Quinolone for DNA)
  4. Cell metabolism (sulfonamide)
  5. Damage to cell membrane (polymixin B)
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12
Q

How does penicillin function?

A

The cyclic oxygen breaks and forms a covalent bond with the enzyme, preventing it from ever being used again.

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13
Q

What kind of enzyme inhibitor is penicillin? What part of the cell does it target?

A

A competitive inhibitor. prevents cell wall synthesis by targeting transpeptidases.

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14
Q

What are some examples of bacteria which were susceptible to penicillin?

A
  • Streptococcus pneumoniae
  • Neisseria meningitidis
  • Treponema pallidum
  • etc.
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15
Q

What is the function of penicillinases?

A

Produced by bacteria to break the ring-structure of penicillin, deactivating it.

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16
Q

What are some examples of semisynthetic penicillins?

A
  • Oxacillin
  • Ampicillin
  • Methicillin
  • Amoxicillin
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17
Q

How have semisynthetic penicillins been modified to prevent deactivation by penicillinases?

A

Have added bulky ring structures which can help prevent the breakdown of the functioning β-lactam ring.

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18
Q

What 2 antimycobacterial antibiotics are important treatments for tuberculosis? What molecule do they inhibit?

A
  1. Isoniazid (INH)
  2. Ethambutol
    Target the synthesis (1) and incorporation of mycolic acid into the cell wall (2).
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19
Q

How does tetracycline function?

A

Binds to the 30S ribosomal subunit to block amino acid incorporation into the growing peptide.

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20
Q

What are some examples of bacteria which are susceptible to tetracycline?

A
  • Rickettsia prowazekii
  • Haemophilus influenzae
  • Chlamydia trachomatis
  • Borrelia burgdorferi
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21
Q

What is meant by MIC?

A

The “minimum inhibitory concentration” at which a drug will still have the desired affect.

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22
Q

What is an example of a bacteria which is susceptible to chloramphenicol?

A

Salmonella enterica (serovar typhi) can be treated with chloramphenicol.

23
Q

What is the general structure of streptomycin? What bacterial families can it be used to control?

A

Three 6-member rings connected by an ether linkage. Used to treat several different kinds of bacterial infection.

24
Q

What part of the bacterial lifecycle does quinolone target? How?

A

DNA replication. By inhibiting DNA gyrase (Gram -ve) or topoisomerase (Gram +ve).

25
Q

What is a noteworthy structural feature of quinolone?

A

A 3-member ring attached to a 6-member ring.

26
Q

What are some examples of bacteria which are susceptible to quinolone?

A
  • Enterobacteriaceae
  • Haemophilus spp.
  • Neisseria spp.
  • Staphylococcus aureus
27
Q

Describe - very generally - the structure of Rifampicin (rifampin).

A

A huge ring structure with other rings incorporated. It just looks like a mess really.

28
Q

What is the function of Rifampicin (rifampin)?

A

As an antibiotic. Prevents mRNA synthesis by binding to the DNA-dependent RNA polymerase.

29
Q

What are some examples of bacteria which are susceptible to Rifampicin (rifampin)?

A
  • Mycobacterium tuberculosis
  • Mycobacterium leprae
  • Staphylococcus aureus (incl. MRSA)
  • Listeria monocytogenes
  • Legionella pneumophila
  • Neisseria meningitidis
  • Neiserria gonorrhoeae
30
Q

What is an example of an antibiotic drug which targets bacterial metabolism? How do these function?

A

Sulfa drugs (sulfonamides), which competitively inhibit purine synthesis.

31
Q

Which 2 sulfa drugs (sulfonamides) are most commonly used in combination with each other?

A

Prontosil and trimethoprim (don’t know if we even need to know this but its on the slides).

32
Q

What are some examples of bacteria which are susceptible to sulfa drugs (sulfonamides)?

A
  • Escherischia coli urinary tract infections

- MRSA (in conjunction with Rifampicin)

33
Q

What is an example of an antibiotic drug which targets the bacterial plasma membrane? How does it act?

A

Polymyxin B. Interacts with phospholipids to disrupt the membrane and cause cytoplasmic leakage.

34
Q

In what 4 ways can antiviral drugs function prior to DNA synthesis?

A
  1. Block viral binding w/ cell
  2. Block viral fusion w/ cell
  3. Prevent viral uncoating
  4. Inhibit viral DNA integration w/ host genome
35
Q

How does Acyclovir function to treat herpes?

A

It is an antiviral drug which blocks DNA synthesis.

36
Q

Why is Acyclovir particularly potent in nerve cells?

A

Because it blocks viral DNA synthesis. Neurons don’t replicate so it specifically targets the viral genes.

37
Q

In what 3 ways can antiviral drugs function after integration of the viral genome with the host?

A
  1. Inhibit DNA or RNA synthesis
  2. Block cleavage of protein precursors
  3. Inhibit exit of virus from host
38
Q

What is the purpose of an interferon?

A

Released by viral-infected cells to inhibit further spread of the infection.

39
Q

What is the purpose of the disk-diffusion method (Kirby-Bauer test)? How does it work?

A

To test the effectiveness of a chemotherapeutic agent. effectiveness is visualized by a zone of inhibition around the antibiotic.

40
Q

What is the function of the E (for epsilometer) test?

A

To measure the antibiotic sensitivity of a bacteria and determine the MIC (minimal inhibitory concentration) needed to prevent growth.

41
Q

What is the function of the broth dilution test? How does it work?

A

To determine the MIC (minimal inhibitory concentration) and MBC (minimal bactericidal concentration). Test by placing in wells of different concentrations.

42
Q

What is an antibiogram?

A

A report which records the susceptibility of organisms encountered clinically.

43
Q

What is a persister cell with regards to antimicrobial resistance?

A

A microbe with a genetic characteristics allowing for their survival when exposed to an antibiotic.

44
Q

What is a superbug with regards to antimicrobial resistance?

A

A bacteria that is resistant to a large number of antibiotics.

45
Q

What is an example of a superbug?

A

Mycobacterium tuberculosis XDR (X-TREME drug Resistance) (lol).

46
Q

How are genes for resistance passed between bacteria?

A

On plasmids or transposons via conjugation or transduction.

47
Q

What are the 4 mechanisms of drug resistance that a microbe may adopt?

A
  1. Block drug binding to the target site
  2. Destruction or inactivation of the drug
  3. Conformation change of the drug’s target site
  4. Rapid efflux of the drug from the microbe
48
Q

What are some examples of antibiotic misuse?

A
  • Using weak or outdated drugs
  • Using drugs that aren’t meant for the condition
  • Using drugs in animal feed
  • Not completing the prescribed drug regimen
  • Using a leftover prescription
49
Q

What is synergism in terms of a drug combination?

A

Where the effect of both drugs together is greater than the effect of either drug alone.

50
Q

What is antagonism in terms of a drug combination?

A

Where the effect of both drugs together is less than the effect of either alone.

51
Q

What are some examples of future chemotherapeutic agents/techniques?

A
  • target virulence factors
  • sequester iron
  • antimicrobial peptides
  • phage therapy
  • bacteriocins
52
Q

What is a bacteriocin?

A

An antimicrobial peptide produced by a bacteria.

53
Q

Rifampicin, an antibiotic, targets bacterial ________ , while quinolone targets ________.

A 
Rifampicin = RNA
Quinolone = DNA

UVic BIOL 459 - Fall 2019 (16 decks)

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