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Micobiology > Chapter 27 > Flashcards

Chapter 27 Flashcards

1
Q

Selective toxicity

A

The ability to inhibit or kill a pathogen without affecting the host

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2
Q

What three things are antimicrobial drugs classified on the basis of?

A
  1. Molecular structure
  2. Mechanism of action
  3. Spectrum of antimicrobial activity
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3
Q

What kind of antimicrobial agents are often used in vivo?

A

Growth factor analogs, sulfa drugs, beta-lactams, protein synthesis inhibitors, Platensimycin, Daptomycin and polymyxin,

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4
Q

Growth factor analogs and sulfa drugs are…

A

synthetic.

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5
Q

Growth factor analogs are structurally similar to what?

A

To growth factors but do not function in the cell

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6
Q

Analogs are similar to…

A

vitamins, amino acids, and other compounds

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7
Q

Sulfa drugs where discovered when?

A

By Gerhard Domagk in the 1930’s

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8
Q

What do sulfa drugs do?

A

They inhibit growth of bacteria

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9
Q

Other synthetic antimicrobials

A
  • Quinolones
  • Also isoniazid for Mycobacteria
  • Nucleic acid base analogs
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10
Q

Beta-lactam antibiotics are:

A

Penicillins and Cephalosporins

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11
Q

What is the most important group of antibiotics of all time?

A

Beta-lactams

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12
Q

What percentage of beta-lactams make up all antibiotics used worldwide?

A

Over half

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13
Q

Who discovered beta-lactams?

A

Alexander Fleming

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14
Q

What are beta-lactams primarily effective against?

A

Gram-positive bacteria

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15
Q

Some synthetic forms of beta-lactams are effective against…

A

some gram-negative bacteria

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16
Q

What do beta-lactams do?

A

Target cell wall synthesis

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17
Q

Many antibiotics effective against Bacteria are also produced by…

A

bacteria

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18
Q

What is an example of a Macrolide?

A

Erythromycin

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19
Q

Erythromycin

A

Broad-spectrum antibiotic that targets the 50% subunit of ribosome

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20
Q

What kind of use is tetracyclines?

A

Widespread medical use in humans and animals

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21
Q

What do tetracyclines do?

A

Broad-spectrum inhibition of protein synthesis; inhibits functioning of 30S ribosomal subunit

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22
Q

What are three protein synthesis inhibitors?

A

Tetracycline, chloramphenicol, and erythromycin

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23
Q

What is Platensimycin?

A

New structural class of antibiotic

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24
Q

How does Platensimycin work?

A

Broad-spectrum, effective against MRSA and vancomycin-resistant enterococci

25
Q

What is Daptomycin and polymyxin produced by?

A

By Streptomyces

26
Q

What do Daptomycin and polymyxin treat?

A

Gram-positive bacterial infections

27
Q

What do Daptomycin and polymixcin do?

A

Forms pores in cytoplasmic membrane

28
Q

Why is it difficult to attain selective toxicity when controlling viruses and eukaryotic pathogens?

A

Most antiviral, antifungal, and antiparasitic drugs also target host structures, resulting in toxicity.

29
Q

What are the most successful and commonly used antivirals?

A

The nucleoside analogs (e.g., AZT and HIV; valacyclovir and herpesvirus)

30
Q

What do nucleoside analogs do?

A

They block reverse transcriptase and production of viral DNA

31
Q

What are nucleoside analogs also called?

A

Nucleoside reverse transcriptase inhibitors

32
Q

What do nonnucleoside reverse transcriptase inhibitors (NNRTI’s) do?

A

They bind directly to RT and inhibit reverse transcription

33
Q

What are two types of anti-HIV drugs?

A

Protease inhibitors and fusion inhibitors

34
Q

What do protease inhibitors do?

A

Protease inhibitors inhibit the processing of large viral proteins into individual components

35
Q

What do fusion inhibitors do?

A

Fusion inhibitors prevent viruses from successfully fusing with the host cell

36
Q

Two categories of drugs successfully limit influenza infection:

A

–Adamantanes –Neuraminidase inhibitors (Tamiflu)

37
Q

What are interferons?

A

Interferons are small proteins that prevent viral multiplication by stimulating antiviral proteins in uninfected cells

38
Q

Topical antifungals target what?

A

A few target unique metabolic processes unique to fungi

39
Q

What does ergosterol do?

A

replaces cholesterol in fungi

40
Q

What do echinocandins do?

A

–Inhibit 1,3 β-D glucan synthase in cell walls
–Used to treat Candida
infections

41
Q

Other drugs target…

A

chitin biosynthesis, folate biosynthesis, or disrupt microtubule aggregation

42
Q

Antimicrobial drug resistance

A

the acquired ability of a microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive

43
Q

Source of resistance genes

A

antibiotic producers

44
Q

Six mechanisms of antibiotic resistance

A 
1. Organism lacks structure the antibiotic inhibits 2. Organism is impermeable to antibiotic 3. Organism can inactivate the antibiotic
(Figure 26.27)
4. Organism may modify the target of the
antibiotic
5. Organism may develop a resistant biochemical
pathway
6. Organism may be able to pump out the
antibiotic (efflux)
45
Q
  1. Organism lacks structure the antibiotic

inhibits

A
  • Mycoplasmas lack cell wall and are resistant to penicillin

* Chromosome

46
Q
  1. Organism is impermeable to antibiotic
A
  • Gram-negative membrane impermeable to penicillin G

* Chromosomal

47
Q
  1. Organism can inactivate the antibiotic
A

Enzymes encoded by R plasmids or the chromosome

48
Q
  1. Organism may modify the target of the antibiotic
A
  • Ribosomes are altered and erythromycin resistance occurs

* Chromosomal

49
Q
  1. Organism may develop a resistant biochemical pathway
A
  • Microbes take up preformed folic acid instead of synthesizing it themselves, rendering them resistant to sulfa drugs
  • Chromosome
50
Q
  1. Organism may be able to pump out the antibiotic (efflux)
A

•Enteric bacteria pump out tetracycline •Plasmid or chromosome

51
Q

R plasmids predate the

A

antibiotic era

52
Q

R plasmids found in cultures frozen before

A

antibiotics used clinically

53
Q

R plasmid genes existed before

A

emisynthetic penicillins were ever made

•R plasmids in soil bacteria

54
Q

The use of antibiotics in medicine, veterinary medicine, and agriculture selects for the spread of R plasmids

A

Overuse of antibiotics

–Used far more often than necessary (e.g., antibiotics used in agriculture as supplements to animal feed)

55
Q

Almost all pathogenic microbes have acquired

A

resistance to some chemotherapeutic agents

56
Q

A few pathogens have developed resistance to all known antimicrobial agents

A

Methicillin-resistant S.

aureus (MRSA)

57
Q

Resistance can be minimized by

A

using antibiotics correctly and only when needed

58
Q

Resistance to a certain antibiotic can be lost if

A

antibiotic is not used for several years

59
Q

Search for new antimicrobials

A

Modify current antimicrobials •Combinatorial chemistry •Computer design – saquinavir binds to active
site of HIV protease •Combinations of drugs •Bacteriophage therapy

Micobiology (19 decks)

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