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Week 2-Day 2 > Antimicrobial Agents & Microbial Resistance > Flashcards

Antimicrobial Agents & Microbial Resistance Flashcards

(51 cards)

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1
Q

Major Inhibition Mechanisms of Antibacterials

A
  1. Cell Wall Synthesis
  2. Membrane Structure
  3. Folate Synthesis
  4. DNA Synthesis
  5. DNA Damage
  6. mRNA Synthesis
  7. Protein Synthesis
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2
Q

Minimum Inhibitory Concentration (MIC)

A

The lowest drug concentration that inhibits VISIBLE growth.

*Every drug has a MIC and MBC

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3
Q

Minimum Bactericidal Concentration (MBC)

A

The lowest drug concentration that kills bacteria.

*Every drug has a MIC and MBC

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4
Q

MIC & MBC

A
  • The lower the number, the more susceptible the bacteria (easily dies).
  • The higher the number, the less susceptible the bacteria (more resistant).
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5
Q

Bacteriostatic

A
  • The drug that prevents the growth of bacteria

- Bacteriostatic MBC&raquo_space; MIC

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6
Q

Bactericidal

A
  • The drug that kills bacteria

- Bactericidal MBC ~= MIC

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7
Q

Pharmacodynamics (PD)

A

The biological effects of the drug ON the BODY.

  • Time, drug concentration, and side effects are important factors.
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8
Q

Pharmacokinetics (PK)

A

The body’s effects ON the DRUG.

  • Time of absorption, distribution, metabolism, excretion are things to be considered.
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9
Q

Time-Dependent Killing (TDK)

A

It is the duration of exposure in which T>MIC for plasma concentration.

Ex. (Wall Inhibitors): Penicillins & Cephalosporins
Ex. (Protein Inhibitors): Macrolides & Clindamycin

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10
Q

Concentration-Dependent Killing (CDK)

A

It is the maximum plasma concentration and therefore the Area Under Curve.

Ex. (DNA Inhibitors): Fluoroquinolones
Ex. (Protein Inhibitors): Aminoglycosides

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11
Q

Post-Antibiotic Effect (PAE)

A

The time it takes bacteria to return to LOG-PHASE growth following removal of antibiotic.

  • CDK drugs have longer PAE than TDK drugs.
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12
Q

Cell Wall Synthesis Inhibitors

A
  • B-lactams

- Glycopetides

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13
Q

Cell Membrane Disrupting Drugs

A
  • Lipopeptides
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14
Q

Subclasses of B-lactams

A
  • Penicillins
  • Cephalosporins (aka. cephamycins)
  • Monobactams
  • Clavams
  • Carbapenems
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15
Q

Peptidoglycan Structure

A
  • Alternating NAM and NAG sugar chains are cross-linked by polypeptide (AAs) bonds.
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16
Q

Transglycosylation

A

Glycosidic bond formation between NAM and NAG sugars.

  • The process is carried out by Transglycosylase.
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17
Q

Transpeptidation

A

Peptide bond formation by removing D-Ala-D-Ala.

  • The process is carried out by Transpeptidase.
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18
Q

Penicillin-Binding Proteins

A

Bacterial proteins that bind to B-lactam antibiotics.

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19
Q

B-lactamases

A

Breaks a bond in the B-lactam ring to disable the antibiotics.

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20
Q

Extended Spectrum B-lactamases (ESBL)

A
  • Most derived from active site mutations in TEM/SHV.

- Results in activity against cephalosporins.

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21
Q

New Delhi Metal-Dependent B-lactamase (NDM-1)

Study These Flashcards
A

One type of B-lactamase I need to know

22
Q

Clavulanic Acid (Generic Name)

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A
  • B-lactamase INHIBITOR

- Belongs to Clavams

23
Q

3 Main Antibiotic Resistance Mechanisms

Study These Flashcards
A
  1. Enzymatically Inactivate Drug
  2. Alter Drug Target
  3. Alter Drug Exposure
24
Q

Subclass of Glycopeptides

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A

Vancomycin

  • Primarily used to treat Gram +
25
Glycopeptides Inhibition
Inhibits Transglycosylation by binding to D-ala-D-ala directly.
26
B-lactam Inhibition
Inhibits Transglycosylation by binding to transpeptidase that is suppose to bind to D-ala-D-ala. ** only work on actively dividing cells (D-ala-D-ala).
27
Anti-Mycobacterial Drugs
1. Isoniazid: Inhibits mycolic acid synthesis. | 2. Ethambutol: Inhibit arabinotransferases.
28
Lipopeptides Generic Drug
Generic Name: Daptomycin
29
Lipopeptide Inhibition
- Antibacterial drug against Gram +. - Binds to phosphatidyl-glycerol in bacterial cell membrane and pokes a hole. - Gram - outer membrane protects against lipopeptides. ** Lipopeptides are not used to treat pneumonia (because lung surfactant layer is rich in phosphatidyl-glycerol) to not damage your lungs.
30
Sulfonamides
- Bacteriostatic drugs against G+ and G- and some protozoa. - Inhibit folate synthesis precursor (DHPS) - Generic Name: sulfamethoxazole (smx)
31
Trimethoprim (tmp)
- Bactericidal - Inhibit folate synthesis precursor (DHFR) - synergistic with smx (becomes bactericidal) in low concentrations against resistance.
32
Fluoroquinolones/Quinolones
- Bactericidal against G- more than G+ - Inhibit DNA Gyrase & topoisomerase IV - Generic Name: Ciprofloxacin
33
DNA Gyrase
Topoisomerase II (releasing knots)
34
Topoisomerase IV
Helps newly replicated chromosomes separate into daughter cells.
35
Rifamycins
- Can be bactericidal or bacteriostatic depending on concentration. - Inhibit mRNA synthesis by binding to bacterial DNA-dp RNA polymerase. - Generic Name: Rifampin
36
Nitroimidazoles
- Bactericidal against anaerobes and some protozoa. - Its prodrug must be converted to active form by bacterial enzyme. - Activated form produce toxic free radicals that damage DNA. - Generic Name: metronidazole
37
Drug Classes Inhibiting Protein Synthesis
1. 30S - Aminoglycosides - Tetracyclines 2. 50S - Chloramphenicol - Macrolides - Lincosamides - Streptogramins - Oxazolidinones
38
Aminoglycosides
- Bactericidal against Gram - and mycobacterium by binding to 30S subunit. - Produced by streptomyces spp. - Generic Name: Streptomycin & Gentamicin - Anaerobes are intrinsically resistant to aminoglycosides
39
B-lactams & Aminoglycosides
They are often prescribed together in combination for synergistic treatment.
40
Tetracyclines
- Bacteriostatic - Bind to 30S subunit. - Generic Name: Tetracycline & Doxycycline
41
Tetracycline & B-lactams
They are combinations to AVOID; Antagonistic
42
Chloramphenicol
- Bacteriostatic (cidal against encapsulated ones) | - Inhibits protein synthesis by binding to 50S subunit.
43
Macrolides
- Bacteriostatic against G+ by binding to 50S subunit. - Produced by streptomyces spp. - Generic Names: Erythromycin & Azithromycin
44
Lincosamides
- Bacteriostatic against G+ and G- anaerobes by binding to their 50S subunit. - Produced by streptomyces spp. - Generic Name: Clindamycin
45
Streptogramins A & B
- Individually bacteriostatic, bactericidal together. - Produced by streptomyces spp. - Bind to 50S subunit.
46
- mycin drugs
Drugs whose generic names end in -mycin are produced by soil bacteria. - erythromycin/azithromycin (macrolides) - clindamycin (lincosamides) - streptomycin/gentamycin (aminoglycosides) - streptogramins (깍두기)
47
Resistance to MLSB
Cross-resistance to Macrolides, Lincosamides, and Streptogramins B. and can lead to multi-drug resistance. - Clindamycin resistance is INDUCIBLE (detected using Disk test) in presence of other drug
48
Resistance to B-lactam
1. Enzymatically Inactivate Drug - Inhibitory enzyme B-lactamase 2. Alter Drug Target - Mutation & Horizontal Genetic Exchange 3. Alter Drug Exposure - Decreased Uptake (in Gram - by altering membrane porins) - Increased Efflux
49
Resistance to Fluo/Quinolones
1. Altered Drug Target - Mutations in gyrase (gyr A) and topoisomerase (parC) genes 2. Altered Drug Exposure - Decreased uptake & increased efflux - Cross-resistance between quinolones and other drugs causing multi-drug resistance
50
Resistance to Rifamycins
Altered Drug Target | - Mutations in RNA polymerase gene
51
Oxazolidinones
- Bacteriostatic against G+ by binding to 50S subunit. | - Generic Name: linezolid

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