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Microbiology > ch 9 antimicrobial chemotherapy > Flashcards

ch 9 antimicrobial chemotherapy Flashcards

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Biology 101 flashcards
1
Q

antibiotic

A

natural products and their derivatives that kill susceptible microorganisms or inhibit their growth

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2
Q

antimicrobial agents

A

includes both natural and chemically synthesized compounds

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3
Q

Ehrlich

A

identified dyes that effectively treated African sleeping sickness
Hata - identified arsenic compounds that effectively treated syphilis
-> all antimicrobial (based on dyes)

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4
Q

penicillin

A

first discovered by Ernest Duchesne 1896
rediscovered by Alexander Fleming 1928
Florey, Chain, and Heatley purified penicillin from culture and injected into mice 1939

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5
Q

streptomycin

A

an antibiotic active against tuberculosis discovered by Waksman 1944

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6
Q

golden era of antibiotics

A

saw the rapid development of new antimicrobial agents that changed how infectious disease was treated and how medicine was and continues to be practiced
1950-1960s

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7
Q

selective toxicity

A

ability to kill or inhibit microbial pathogen while damaging the host as little as possible

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8
Q

the degree of selective toxicity can be expressed in terms of

A

1 The therapeutic dose - the drug level required for the treatment of a particular infection
2 the toxic dose - the drug level at which the agent becomes too toxic for the host
3 therapeutic index - the ratio of the toxic does to the therapeutic dose
- the larger the therapeutic index, the better the chemotherapeutic agent in general

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9
Q

narrow-spectrum drugs

A

effective only against a limited variety of pathogens

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10
Q

broad-spectrum drugs

A

target many different kinds of bacteria

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11
Q

cidal

A

kills the target pathogen, may be static at low levels

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12
Q

static

A

reversibly inhibit growth

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13
Q

minimal inhibitory conc (MIC)

A

lowest conc of a drug that prevents growth of a particular pathogen

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14
Q

minimal lethal conc (MLC)

A

lowest drug conc that kills the pathogen

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15
Q

dilution susceptibility test

A

used to determine MIC and MLC values
involves inoculating media containing different concs of drugs
- broth or agar with lowest conc showing no growth is MIC
- MLC is ascertained when tubes that show no growth are then cultured into fresh medium lacking antibiotic - lowest antibiotic conc that fails to support the microbe’s growth is MLC

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16
Q

disk diffusion test

A

often used to analyze rapidly growing bacteria
- disks impregnated with different antibiotics are place on agar plates inoculated with a microbe
- observe zones of clearing around disks

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17
Q

kirby-bauer method

A

most common disk diffusion test
relates zone diameter with microbial resistance
used to determine if effective conc of drug in body can be reached

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18
Q

Etest

A

used in sensitivity testing
Etest strips contain a gradient of an antibiotic, intersection of elliptical zone of inhibition with strip indicates MIC
- can only test 1 agent at a time, expensive

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19
Q

main modes of antibacterial drug action

A
  • inhibitors of cell wall synthesis
  • most selective against bacteria bc they target structures and functions not found in eukaryotes
  • protein synthesis inhibitors
  • metabolic antagonists
  • nucleic acid synthesis inhibition
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20
Q

beta-lactam ring

A

the cyclic chemical structure composed of one nitrogen and three carbon atoms, it has antibacterial activity, interfering with bacterial cell wall synthesis - block transpeptidation
most crucial feature of penicillin
essential for bioactivity

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21
Q

penicillinase

A

beta-lactamase
enzymes that inactivate the antibiotic by hydrolyzing a bond in the beta-lactam ring
- found in penicillin-resistant bacteria

22
Q

penicillin G and V

A

naturally occurring penicillin
narrow-spectrum - effective against many gram-positive pathogens

23
Q

semisynthetic penicillins

A

have a broader spectrum than naturally occurring ones
- bulkier side chains make them more difficult for b-lactamase to degrade

24
Q

cephalosporins

A

structurally and functionally similar to penicillins
- inhibit transpeptidation reaction during peptidoglycan synthesis
effective against gram-negative

25
Q

carbapenems and monobactams

A

developed in mid-1980s in response to growing concern of antibiotic resistance
part of the beta-lactam family
carbapenems - effective against broad spectrum of bacteria
monobactam - only effective against gram-negative

26
Q

vancomycin

A

glycopeptide antibiotic produced by streptomyces orientalis
blocks transpeptidase activity (inhibits cell wall synthesis) binds to enzyme’s substrate
drug of last resort
important for treatment of antibiotic-resistant staphylococcal and enterococcal infections

27
Q

protein synthesis inhibitors

A
  • aminoglycosides
  • tetracyclines
  • macrolids
  • lincosamides
  • oxazolidinones
28
Q

inhibitors of cell wall synthesis

A
  • penicillin
  • cephalosporins
  • carbapenems and monobactams
  • vancomycin
29
Q

aminoglycosides

A

contain cyclohexane ring and amino sugars
bactericidal - used for gram-negative
disrupt peptide elongation in translation, cause early termination of peptide synthesis

30
Q

tetracyclines

A

four-ring structure with a variety of side chains
bacteriostatic, broad spectrum
target 30S subunit, inhibiting protein synthesis

31
Q

macrolides

A

contain a ring structure of 12-22 carbon lactone rings linked to one or more sugars
bacteriostatic, broad spectrum, mostly gram-positive some negative
target the 50S subunit to inhibit translation
used for patients allergic to penicillin

32
Q

lincosamides

A

produced by streptomyces bacteria
broad spectrum of antibiotic activity against anaerobic microbes
can cause life-threatening diarrheal infection
clindamycin used to treat dental infections

33
Q

oxazolidinones

A

synthetic drug with heterocyclic five-membered ring structure
bacteriostatic
bind to a site on the 23S rRNA within the 50S ribosomal subunit before protein synthesis has begun to prevent assembly of 70S initiation complex
linezolid - active against MRSA (resistant to beta-lactams)

34
Q

metabolic antagonists

A
  • sulfonamides
  • trimethoprim
35
Q

sulfonamides/sulfa drugs

A

structural analogues of PABA which is needed for folic acid synthesis needed for synthesis of purines
prevent the synthesis of DNA, RNA, and proteins and other important cellular constituents
high therapeutic index

36
Q

trimethoprim

A

synthetic antibiotic that interferes with the production of folic acid at a later step
broad spectrum
usually combined with sulfa drugs to increase efficacy

37
Q

nucleic acid synthesis inhibitors

A
  • fluoroquinolones
  • rifamycins
38
Q

fluoroquinolones

A

synthetic drug containing fluorinated 4-quinolong ring
bind to the bacterial topoisomerases DNA gyrase and topoisomerase IV to disrupt DNA replication and repair and bacterial chromosome separation during division
bactericidal, broad spectrum
can affect eukaryotic DNA as well - drug of last resort

39
Q

rifamycins

A

inhibit bacterial transcription by binding the the beta-subunit of RNA polymerase

40
Q

antiviral drugs

A

small molecules that inhibit virus-specific-enzymes and replication cycle processes
- simply limit the duration of the illness or its severity, not a cure

41
Q

antiviral drugs for influenza

A

oseltamivir - neuraminidase inhibitor
not a cure, shorten course of illness
marboxil baloxavir - prevents cap snatching when host’s 5’ caps are added to viral transcripts

42
Q

antiviral drugs for herpesviridae family

A

exploit that fact that they have their own enzyme to phosphorylate nucleosides to nucleotides
nucleoside analogs that are incorporated into viral genome block further DNA synthesis
- forsarnet, cidofovir, acyclovir

43
Q

five categories of anti-HIV drugs

A
  1. nucleoside reverse transcriptase inhibitors (NRTIs) - nucleoside analogues causing chain termination
  2. nonnucleoside reverse transcriptase inhibitors (NNRTIs) - bind and inhibit the viral reverse transcriptase enzyme
  3. protease inhibitors (PIs) - block the activity of the HIV protease needed for the production of viral proteins
  4. integrase inhibitors - prevent incorporation of the HIV genome into the host’s chromosomes
  5. fusion inhibitors (FIs) - prevent HIV entry into cells
44
Q

hepatitis C virus cure

A

RNA virus
leading cause of liver transplant
use direct-acting antiviral agents:
- nucleotide analogue that block HCV-RNA polymerase
- target viral enzyme needed for replication

45
Q

antifungal drugs

A

fewer effective agents bc eukaryotic fungal cell and human cell are similar
- many have low therapeutic index and are toxic
most are fungistatic

46
Q

two classes of antifungal drugs

A

polyenes - nystatin
azoles - itraconazole
both block fungal cell membrane synthesis

47
Q

mycoses

A

superficial and cutaneous mycoses (athletes foot, ring worm)
- infections of skin and hair
- treated with topical forms of azole drugs, some oral
- disrupts mitotic spindles, preventing cell division
systemic mycoses
- difficult to control and can be fatal, fungus invades other organs
- treated with amphotericin B, 5-flucytosine (disrupts RNA function), fluconazole

48
Q

echinocandins

A

more recently developed class of anti-fungal drug
block the synthesis of fungal cell wall bu inhibiting the enzyme beta (1,3)-D-glucan synthesis, which links glucan subunits

49
Q

antiprotozoan drugs

A

not many bc protozoa are eukaryotes
quinine - for malaria
- suppresses plasmodium reproduction and are effective in eradicating asexual stages of the protozoan’s life cycle that occur in red blood cells

50
Q

two types of drug resistance

A

intrinsic - mycoplasma resistance to beta-lactam antibiotics and other cell wall inhibitors simply bc these bacteria lack a cell wall
acquired - occurs when there is a change in the genomes of a bacterium that converts it to become resistance

51
Q

mechanisms of drug resistance

A
  • modify the target of the antibiotic
  • drug inactivation/degrading
  • minimize conc of antibiotic in the cell
  • bypass the biochemical reaction inhibited by the agent or inc the production of the target metabolite
52
Q

overcoming drug resistance

A
  • give drug in high enough conc to destroy susceptible microbes and most spontaneous mutants
  • educate patients to finish course of therapy
  • give two or more drugs at the same time
  • use drugs only when necessary

Microbiology (13 decks)

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