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Microbiology > Exam 3- Antimicrobials > Flashcards

Exam 3- Antimicrobials Flashcards

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1
Q

For an antimicrobial drug to have selective toxicity it needs to…

A

kill microbial cells but not host cells

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2
Q

What is a broad spectrum for antimicrobials?

A

effective against wide range of species, including both gram negative & positive species

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3
Q

What is a narrow spectrum for antimicrobials?

A

only active against select species

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4
Q

What is used to determine effectiveness of chemical agents against a particular microbe?

A

a disk-diffusion assay

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5
Q

What is minimal inhibitory concentration?

A

MIC, lowest concentration of the drug that inhibits growth of the microbe

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6
Q

What is used to determine the MIC of a drug?

A

a broth dilution test

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7
Q

What is a therapeutic dose?

A

minimum dose per kg of body weight that inhibits growth of the pathogen

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8
Q

What is a toxic dose?

A

maximum dose tolerated by the patient

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9
Q

What is the chemotherapeutic index?

A

ration of the toxic dose to therapeutic dose

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10
Q

When does synergism occur?

A

when the effect of two drugs together is greater than the effect of either alone

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11
Q

When does antagonism occur?

A

when the effect of two drugs together is less than the effect of either alone

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12
Q

Why do antibiotics exhibit selective toxicity?

A

because they disturb enzymes or structures unique to the target cell

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13
Q

What is penicillinase (beta-lactamase)?

A

a beta-lactamase enzyme effective against penicillin

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14
Q

What is bacitracin?

A

large polypeptide produced by Bacillus subtilis & Bacillus licheniformis

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15
Q

What does bacitracin do?

A

inhibits cell wall synthesis by binding to the bactoprenol lipid carrier molecule that exports peptidoglycan disaccharide units across cell membrane

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16
Q

What is vancomycin?

A

very large, complex glycopeptide produced by Amycolatopsis orientalis

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17
Q

What does vancomycin do?

A

binds peptide end of newly exported NAM-NAG disaccharide & blocks addition to preexisting peptidoglycan

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18
Q

What is mycobacterium?

A

cell wall contains mycolic acids & arabinogalactans

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19
Q

What does isoniazid do?

A

INH, inhibits mycolic acid synthesis

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20
Q

What does ethambutol do?

A

disrupts arabinogalactan synthesis

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21
Q

What is polymyxin?

A

positively charged polypeptide ring from Bacillus polymyxa that binds to the outer & plasma membranes of bacteria, both of which are negatively charged

22
Q

What is inhibit replication?

A

bacterial replication uses enzymes that closely resemble human enzymes

23
Q

What are quinolones?

A

drugs that target topoisomerases like DNA gyrase, which introduces negative supercoils in DNA ahead of replication forks

24
Q

What are rifamycin?

A

class of drugs that includes rifampin that selectively binds to the bacterial RNA polymerase

25
Q

Why does erythromycin have a spectrum of activity limited mostly to gram-positive bacteria?

A

erythromycin is blocked by the gram negative cell wall. gram positive bacteria accumulate 100-fold more erythromycin than gram negative bacteria

26
Q

What do sulfonamides do?

A

inhibit folic acid synthesis

27
Q

What is folic acid?

A

an important cofactor in the synthesis of nucleic acid precursors

28
Q

What are selectively toxic targets for anti-fungal drugs?

A

ergosterol & beta-glucan

29
Q

What are the 4 antifungal drugs licensed for use in humans?

A
  1. polyenes
  2. flucytosine
  3. echinocandins
  4. azoles
30
Q

What do polyenes do?

A

disrupt cell membranes by binding ergosterol

31
Q

What does flucytosine do?

A

fluorouracil disrupts RNA synthesis; derivatives of FU disrupt DNA synthesis

32
Q

What do echinocandins do?

A

disrupt cell wall synthesis through inhibition of glucan synthase

33
Q

What do azoles do?

A

block ergosterol biosynthesis through inhibition of lanosterol demethylase

34
Q

What are antiviral agents hard to discover?

A

there are very few drugs targets unique to viruses

35
Q

What is acyclovir?

A

guanosine analog that lacks a 3’ OH

36
Q

What is only found in viruses?

A

RNA-directed RNA polymerase

37
Q

What is Ribavirin?

A

ribonucleoside analog that resembles guanosine or adenosine; when incorporated into RNA, can pair with either uracil or cytosine

38
Q

What is ribavirin used to treat?

A

Hep C virus

39
Q

Explain the influenza virus.

A

an enveloped virus with glycoprotein spikes

40
Q

What does hemagglutinin do?

A

binds to the host membrane sialic acid receptors for entry by endocytosis

41
Q

What does neuraminidase do?

A

cleaves sialic acid to allow virus particles to escape from infected cells

42
Q

What do Zanamivir & oseltamivir (tamiflu) inhibit?

A

neuraminidase, prevents release of mature virus

43
Q

What does penicillin interfere with?

A

peptidoglycan synthesis

44
Q

Selective toxicity of penicillin.

A

because human cells do not have cell walls & do not synthesize peptidoglycan

45
Q

What are the mechanisms of antibiotic resistance?

A

modify the target, destroy the antibiotic, add modifying groups, pump the antibiotic out

46
Q

How do bacteria acquire antibiotic resistance?

A

can arise spontaneously through mutation or gene duplication followed by random mutations that repurpose the duplicated gene or genes

47
Q

What is horizontal transfer?

A

once resistance mechanism develops, resistance can spread from cell to cell & from species to species

48
Q

How many people get sick with antibiotic-resistant infections per year?

A

2.8 million

49
Q

How many people die from antibiotic-resistant infections per year?

A

35,000

50
Q

What can broad-spectrum antimicrobial use lead to?

A

development of a superinfection

51
Q

Misuse of antibiotics include..

A

not completing a prescribed course of antibiotics, using them for the common cold & other inappropriate conditions, using antibiotics in animal feed

Microbiology (11 decks)

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