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Microbiology - Quiz 2 > Antibiotics > Flashcards

Antibiotics Flashcards

(62 cards)

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1
Q 
Mupirocin:
Class?
Action?
Bacteriostatic/cidal?
Species range?
Applications?
A

Translation inhibitor
Binds isoleucyl-tRNA synthetase, so no charged ile-tRNA available
Bacteriostatic at low concentrations, cidal at higher (with topical administration)
Used in surgeons to prevent transmission of MRSA from nasal cavity

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2
Q 
Ciprofloxacin:
Class?
Action?
Bacteriostatic/cidal?
Species range?
Applications?
A

Fluoroquinolone (DNA replication inhibitor)
Inhibits DNA gyrase and thus DNA synthesis
Bacteriocidal
Broad spectrum: Gm- enterics, G+ cocci, Pseudomonas
Resistance emerging
Not for kids or pregnant women

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3
Q 
Moxifloxacin:
Class?
Action?
Bacteriostatic/cidal?
Species range?
Applications?
A

Fluoroquinolone (DNA replication inhibitor)
Inhibits DNA gyrase AND topoisomerase activity (less susceptible to resistance)
Bacteriocidal
Broad spectrum: Gm- enterics, G+ cocci, Pseudomonas, MRSA
Not for kids or pregnant women

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4
Q 
Metronidazole:
Class?
Action?
Bacteriostatic/cidal?
Species range?
Applications?
A

Nitroimidazole (DNA replication inhibitor)
Activated form (in anaerobic conditions) binds DNA and fragments it
Bacteriocidal
Useful against anaerobic bacterial, protozoa

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5
Q 
Rifampin:
Class?
Action?
Bacteriostatic/cidal?
Species range?
Applications?
A

RNA synthesis inhibitor
Binds beta subunit of RNA pol, inhibiting transcription
Bacteriocidal
Broad spectrum
Effective prophylactic against N. menigitidis b/c secreted in saliva
Resistance develops rapidly, used in combo

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5
Q

Example of antagonistic combined antibiotic action

A

Penicillin (requires growth) given with bacteriostatic agent (tetracycline)

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6
Q 
Ethambutol and pyrazinamide:
Class?
Action?
Bacteriostatic/cidal?
Species range?
Applications?
A 
Anti TB drugs
Unknown mechanism of action
E- static, P- cidal once activated
Narrow spectrum (TB)
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7
Q

Example of synergistic combined antibiotic action

A

Agent which damages cell wall/membrane with cidal agent taken up poorly by bacterium

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8
Q

Indications for combined use of antibiotics (5)

A 
Synergistic activity expected
Pathogen requires more than one agent
Likelihood of resistance reduced
Dosage of toxic drug can be reduced
Polymicrobial infection requires use of more than one agent
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9
Q

Disadvantages of combined antibiotics (4)

A

Increased risk of side effects
Increased risk of superinfections
Possible antagonism
Increased cost

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10
Q

4 general reasons for antibiotic inactivity

A
  1. Enzyme inactivation: antibiotic is inactivated (extracellular, intracellular, both)
  2. Altered membrane permeability/antibiotic efflux: antibiotic can’t enter cell or is actively pumped out
  3. Alteration of ribosomal/cell wall precursor/enzyme targets: bacterial cell contains altered enzyme that resists action of antibiotic
  4. Bypass pathways: antibiotic enters cell but drug-binding target site is replaced
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11
Q

Mechanisms of resistance to trimethoprim

A

Plasmid-coded, trimethoprim-resistant dihydrofolate reductase

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12
Q

Mechanisms of resistance to penicillins (3)

A

Hydrolysis of beta-lactam ring by beta-lactamase
Decreased cephalosporins permeability of bacteria
Altered penicillin binding proteins

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13
Q

Mechanisms of resistance to methicillin

A

Altered penicillin binding proteins

Beta-lactamase resistant

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14
Q

Mechanisms of resistance to aminoglycosides (3)

A

Enzymatic modification of drug by plasmid-coded enzyme
Decreased permeability to antibiotic
Altered antibiotic binding site

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15
Q

Mechanisms of resistance to tetracyclines

A

Interference with transport of drug into cell

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16
Q

Mechanisms of resistance to chloramphenicol

A

Detoxification of drug by acetylation of hydroxyl

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17
Q

Mechanisms of resistance to erythromycin

A

Enzymatic methylation of 23S ribosomal RNA

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18
Q

Mechanisms of resistance to ciprofloxacin/rifampin

A

Altered target enzymes (gyrase, RNAP)

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20
Q

Mechanisms of resistance to vancomycin

A

Alteration of cell wall precursor target

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21
Q

Characteristics of an ideal antibiotic (4)

A

Target one or more bacterial species with no toxicity or allergy
Persist long enough to destroy target
Not lose effectiveness due to bacterial resistance
Achieve effective concentrations in sites of infection

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22
Q

Define bacteriostatic

A

Stops growth of bacteria for a time

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23
Q

Define bacteriocidal

A

Kills bacteria

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24
Q

What is the Kiby-Bauer disc diffusion method? How does it work?

A

Allows you to test the sensitivity of multiple antibiotics against a given strain

Plate purified bacteria on agar plate
-> Add filter paper discs with antibiotic onto the surface
-> Measure circular zones of inhibition of bacterial growth around each disc
(inhibition = sensitivity, growth = insensitivity)

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25
How can you test for beta-lactamase production?
Plate bacteria on nitrocefin, which is chromogenic and has a beta-lactam ring sensitive to hydrolysis
26
What is the MIC? How can you test for it?
MIC = minimum inhibitory concentration Inoculate tubes with same amount of bacteria Add serial dilution of antibiotic MIC= lowest amount of antibiotic needed to inhibit growth
27
What is MBC? How can you test for it?
MBC = minimum bacteriocidal concentration Perform MIC test, then plate bacteria in absence of antbiotic to see if they grow or if they were killed by antibiotic
28
Define antimetabolite.
Interferes with the synthesis or function of a substance involved in normal cell metabolism Often structurally similar to the natural substance
29
``` Sulfonilamide: Class? Action? Bacteriostatic/cidal? Species range? Application? ```
``` Sulfonamide (antimetabolite) Inhibits synthesis of folic acid -> lack of DNA synthesis Bacteriostatic Broad range of species Used for UTIs (concentrated in urine) ```
30
``` Trimethoprim: Class? Action? Bacteriostatic/cidal? Application? ```
Antimetabolite Inhibits later step in folic acid metabolism (dihydrofolate reductase = present in humans, but much higher affinity for bacterial enzyme) Bacteriostatic Used for UTIs
31
``` Bactrim: Class? Action? Bacteriostatic/cidal? Application? ```
Antimetabolite Combination of sulfamethoxazole and trimethoprim for a synergistic effect Bacteriostatic Used for UTIs
32
``` Isoniazid: Class? Action? Bacteriostatic/cidal? Species range? ```
Antimetabolite Inhibits synthesis of mycolic acid, found in the cell walls of mycobacteria Bacteriocidal Narrow - specific to M tuberculosis Efficient cellular penetration (intracellular)
33
Penicillins: why the large difference in sensitivity between bacterial and animal cells? Bacteriostatic or bacteriocidal? What conditions are required?
Difference in sensitivity because there is no cell wall in animal cells Bacteriocidal Growth is essential for action - inhibit peptidoglycan synthesis
34
Basic structure of penicillins. What are they sensitive to? (2 things)
Have beta-lactam and thiazolidine rings | Sensitive to hydrolysis by stomach acids and beta-lactamases
35
Mechanism of action of penicillins
Beta-lactam = structural analog of peptidoglycan pentapeptide - bind to and inactive penicillin-binding proteins (PBPs): transpeptidases that are responsible for cross-linking (the final step in cell wall assembly)
36
``` Penicillin G: Class? Action? Bacteriostatic/cidal? Species range? Application? Sensitivity? ```
``` Penicillin (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Ineffective against Gm- enterics Acid-labile - cannot be taken orally Sensitive to beta-lactamases ```
37
``` Penicillin V: Class? Action? Bacteriostatic/cidal? Species range? Application? Sensitivity? ```
``` Penicillin (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Ineffective against Gm- enterics Resist acid hydrolysis - can take orally Sensitive to beta-lactamases ```
38
``` Ampicillin/amoxicillin: Class? Action? Bacteriostatic/cidal? Species range? Application? Sensitivity? ```
Penicillin (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Broader spectrum: effective against Gm- enterics Resist acid hydrolysis - can take orally Sensitive to beta-lactamases Amoxicillin = higher serum levels
39
``` Tricarcillin: Class? Action? Bacteriostatic/cidal? Species range? Application? Sensitivity? ```
Penicillin (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Extended spectrum - effective against Gm- enterics and Pseudomonas aeruginosa Sensitive to beta-lactamases
40
``` Piperacillin: Class? Action? Bacteriostatic/cidal? Species range? Application? Sensitivity? ```
Penicillin (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Extended spectrum - the most active penicillin against Gm- enterics and Pseudomonas aeruginosa Sensitive to beta-lactamases
41
``` Methicillin: Class? Action? Bacteriostatic/cidal? Species range? Application? Sensitivity? ```
Penicillin (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Narrow spectrum - antistaphylococcal! for resistant staph Resistant to beta-lactamases Acid-labile - cannot be taken orally
42
``` Oxacillin: Class? Action? Bacteriostatic/cidal? Species range? Application? Sensitivity? ```
Penicillin (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Narrow spectrum - antistaphylococcal! for resistant staph Resistant to beta-lactamases Resist acid hydrolysis - can take orally
43
``` Cefazolin: Class? Action? Bacteriostatic/cidal? Species range? ```
Cephalosporin (beta-lactam antibiotic, cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Most active versus Gm+ cocci and some Gm- enterics
44
``` Cefuroxime: Class? Action? Bacteriostatic/cidal? Species range? ```
Cephalosporin (beta-lactam antibiotic, cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Most active versus Gm- enterics, less effective against Gm+
45
``` Ceftriaxone/ceftazidime: Class? Action? Bacteriostatic/cidal? Species range? Sensitivity? ```
Cephalosporin (beta-lactam antibiotic, cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Very broad spectrum, active against P. aeruginosa Increased beta-lactamase resistance
46
Differences between cephalosporins and penicillins (5, 2 similarities)
Both have beta-lactam rings Both bacteriocidal Cephalosporins: Have dihydrothiazine vs thiazolidine ring Generally broader spectrum Greater acid stability Resist some beta-lactamases Good for penicillin allergies (antigenically dissimilar)
47
``` Aztreonam: Class? Action? Bacteriostatic/cidal? Species range? Sensitivity? ```
Monobactam (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Specific to Gm- aerobes including P. aeruginosa Resistant to beta-lactamases Minimal cross-immunogenicity with other beta-lactams
48
``` Imipenem: Class? Action? Bacteriostatic/cidal? Species range? Sensitivity? ```
``` Carbapenem (cell wall synthesis inhibitor) Inhibits penicillin-binding proteins Bacteriocidal Broadest spectrum Resistant to beta-lactamases Susceptible to renal dispeptidase ```
49
What s a beta-lactamase inhibitor? Name two.
Beta-lactams which have minimal activity as antibiotics but extend the use of beta-lactam antibiotics ``` Clavulanic acid (used with amoxicillin -> augmentin) Sulbactam ```
50
``` Vancomycin: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
Glycopeptide cell wall synthesis inhibitor Binds R-D-Ala-D-Ala - blocks peptidoglycan precursor transfer Bacteriocidal Restricted to Gm+ Toxic - used for MRSA and multiply resistant enterococcus VRSA now identified
51
``` Cycloserine: Class? Action? Bacteriostatic/cidal? Species range? ```
Cell wall synthesis inhibitor Inhibits D-alanine steps Bacteriocidal Secondary tuberculosis drug
52
``` Bacitracin: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
``` Cell wall synthesis inhibitor Inhibits lipid carrier step Bacteriocidal Restricted to Gm+ Toxic - used for topical therapy ```
53
``` Polymyxin B: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
Cell membrane permeabilizer Bind LPS, then membrane phospholipids, leading to membrane leakage Bacteriocidal (does NOT require growth) Selective for Gm- enteric rods, esp. Pseudomonas Toxic, so topical only
54
``` Streptomycin: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
Aminoglycoside (translation inhibitor) Binds 30S subunit, distorts acceptor site -> misreading -> bad proteins -> leaky membranes Bacteriocidal due to membrane effects Inhibited by anaerobic or acidic conditions Not good for urine Toxic!
55
``` Gentamicin: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
Aminoglycoside (translation inhibitor) Binds multiple sites on the 30S subunit (less resistance) -> leaky membranes Bacteriocidal due to membrane effects Inhibited by anaerobic or acidic conditions Toxic!
56
``` Tetracycline/doxycycline/minocycline: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
``` Tetracyclines (translation inhibitors) Block binding of aminoacyl tRNA to 30S Bacteriostatic Broad spectrum, also useful for intracellular parasites Not used for pregnancy or young children Wipe out normal flora ```
57
``` Erythromycin: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
``` Macrolide (translation inhibitor) Blocks chain elongation Bacteriostatic Broad spectrum, includes mycoplasma and chlamydia Widely used ```
58
``` Azithromycin: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
``` Macrolide (translation inhibitor) Blocks chain elongation, but higher tissue concentrations than erythromycin Bacteriostatic Slightly larger range than erythromycin Widely used ```
59
``` Chloramphenicol: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
Translation inhibitor Blocks chain elongation Bacteriostatic, can be cidal Used for anaerobes, particularly enterics Not widely used because of toxicity (lethal aplastic anemia)
60
``` Clindamycin: Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
Translation inhibitor Inhibits peptidyl transfer Bacteriostatic Active against Gm+, especially active against anaerobes
61
``` Dalfopristin/quinupristin [Synergin] Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
Streptogramins (translation inhibitors) Bind to 50S subunit Bacteriostatic Useful against resistant bacteria, especially because of synergistic combination
62
``` Linezolid (Zyvox): Class? Action? Bacteriostatic/cidal? Species range? Applications? ```
Oxazolidinone (translation inhibitor) Interacts with 16S and 23S rRNA, inhibit tRNA translocation Bacteriostatic Useful against resistant bacteria

Microbiology - Quiz 2 (10 decks)

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