Lecture 12 - Drugs, Microbes and Hosts Flashcards

1
Q

Three factors must be known before starting antimicrobial therapy:

A
  • The identity of the microorganism causing the infection
  • the degree of the microorganisms susceptibility to various drugs
  • the overall medical condition the patient
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2
Q

Small discs containing premeasured amounts of antibiotics are dispensed onto the bacterial lawn
A zone of inhibition formed during incubation is measured and compared with a standard for each drug

A

kirby-bauer technique

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3
Q

profile of antimicrobial sensitivity

A

antibiogram

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4
Q
  • the smallest concentration (highest dilution) of drug that visibly inhibits growth
  • Useful in determining the smallest effective dosage of a drug
  • Provides a comparative index against other antimicrobials
  • performed by automated machinery
A

tube dilution tests - minimum inhibitory concentration

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5
Q

reasons why treatment can fail

A
  • inability of the drug to diffuse into that body comportment
  • resistant microbes the infection that didn’t make it into the sample collected for testing
  • an infection caused by more than one pathogen
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6
Q
  • The ratio of the dose of the drug that is toxic to humans to its minimum effective dose
  • The closer these two figures are to each other (the smaller the ratio), the greater potential for toxic drug reactions
A

therapeutic index

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7
Q
  • Central concept in antibiotic treatment
  • Antimicrobial drugs should kill or inhibit microbial cells without simultaneously damaging host tissues
  • The best drugs in current use block the actions or synthesis of molecules in microorganisms but not vertebrate cells
A

selective toxicity

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8
Q
  • Effective against more than one group of bacteria Example: tetracyclines
A

Broad spectrum drugs:

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9
Q
  • Only target a specific group

- Examples: polymyxin and penicillins

A

narrow spectrum drugs

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10
Q

Can be obtained naturally or synthesized in the laboratory
Consist of three parts: Thiazolidine ring
Beta lactam ring
Variable side chain

A

penicillin

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11
Q

Isolated in the 1940s from Cephalosporium
acremonium
Have a beta-lactam ring that can be chemically altered
Similar mode of action to penicillins

A

cephalosporins

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12
Q

Derived from Bacillus polymyxa Toxic to the kidney

A

polymyxins

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13
Q
High potency
  Broad spectrum
  Readily absorbed from the intestine
  Side effects:
  Seizures and other brain disturbances
A

fluoroquinolones

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14
Q

Composed of one or more amino sugars and an aminocyclitol ring
Products of actinomyces Streptomyces
Micromonospora
Broad antimicrobial spectrum

A

amino glycoside drugs

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15
Q

Natural parent compound and synthetic derivatives
Broad spectrum effects
Side effects:
Gastrointestinaldisruption Deposition in hard tissues

A

tetracyclines

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16
Q

Newer derivatives of tetracyclines
Block 30s ribosomal subunit
Effective against bacteria that have become resistant to tetracyclines

A

glycylcyclines

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17
Q

Macrolide ring

Broad spectrum, low toxicity

A

erythromycin

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18
Q

adverse reactions theGI tract limits its use

A

clindamycin

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19
Q

respiratory tract infections suspected to be caused by resistant microbes

A

telithromycin

20
Q

Synthetic: do not originate from bacteria or fungi

A

sulfonamides

21
Q

Interrupting quorum sensing pathways

Adding DNase to antibiotics Pretreatment

A

treatment of biofilms

22
Q

Quinine: principal treatment for hundreds of years Replaced by chloroquine and primaquine: less toxicity

A

antimalarial drugs

23
Q

chemotherapy for other protozoa infections

A

metronidazole: amoebicide

24
Q

anthelminthic drug therapy:

A

Mebendazole and albendazole
Pyrantel
Praziquantel

25
Three major modes of action in antiviral chemotherapeutic agents:
Barring penetration of the virus into the host cell Blocking the transcription and translation of viral molecules Preventing maturation of viral particles
26
how does drug resistance develop
resistance through - spontaneous mutation - horizontal transfer - sharing of resistance genes
27
Plasmids that are transferred through conjugation, transformation, or transduction
resistance factors
28
duplicated and inserted from one plasmid to another or from the plasmid to the chromosome
transposable drug resistance sequences
29
new enzymes are synthesized
- inactivate the drugs | - only occurs when new genes are acquired
30
permeability or uptake of the drug into a bacterium is decrease
- occurs via mutation
31
- drug is immediately eliminated
- acquisition of new genes
32
- binding sites for drugs are decreased in number or affinity
can occur via mutation or acquisition of new genes
33
an affected metabolic pathway is shut down or alternative pathway is used
- occurs due to mutation of original enzyme or enzymes
34
long term strategies to control drug resistance
- restriction of the use of first line antibiotics | - enhanced surveillance mechanisms
35
- PulseNet, WHONET - Track foodLborne pathogens and pathogenic microbial populations - Provides up to date views of the changes in resistance genes
surveillance mechanisms
36
Finding new targets in the bacterial cell | Customizing drugs that aim for these new targets
past approach
37
Disabling host molecules that the invaders use to enhance their position
novel approach
38
Using bacteriophages in Eastern European countries Incorporating phage into wound dressings Phage are extremely specific and only infect one species of bacteria, leaving normal microbiota alone
low tech solutions
39
Preparations of live microorganisms fed to animals and humans to improve intestinal biota Replace microbes lost during antimicrobial therapy Augment the biota already there
probiotics
40
Nutrients that encourage the growth of beneficial | microbes in the intestine
prebiotics
41
Bind to the enamel of teeth, causing a permanent gray to brown discoloration Cause liver damage in pregnant women Cross the placenta and are deposited in fetal bones and teeth
tetracycline
42
Most common complaint associated with oral antimicrobial therapy Can progress to severe intestinal irritation or colitis Some drugs directly irritate the intestinal lining Also caused by disruption of the intestinal microbiota
diarrhea
43
Drug acts as an antigen that stimulates the allergic response Can be provoked by the intact drug molecule or alteration of the drug
allergy
44
Treats infection | Destroys normal biota, even those far removed from the original infection
broad spectrum antimicrobial
45
Beneficial resident species are destroyed through antibiotic therapy Microbes once small in number begin to overgrow and cause disease
superinfection