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Pharm Exam 1 > Antibiotics 1 > Flashcards

Antibiotics 1 Flashcards

1
Q

What is the “real” definition of “antibiotic” and how does that differ from the way it is typically used in veterinary medicine?

A

“against life”
Substance produced by one organism that acts against another microbe
Commonly used to mean any drug against bacteria regardless of origin

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2
Q

Define Microbe

A

bacteria, viruses, fungi, and

protozoa

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3
Q

What things do you consider when classifying an Abx?

A
  1. Spectrum
  2. Effect on bacteria (-cidal vs -static)
  3. MOA
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4
Q

What would constitute a drug with a narrow spectrum of activity versus a drug with a broad spectrum of activity?

A

Broad Spec
–Active against Gram+ AND Gram-

Narrow Spec

  • Effective against selective populations
    • ex. only aerobes or only Gram+
  • based on:
  • –Environment (aerobe vs anaerobe)
  • –Bacterial characteristics (Gram Pos vs Neg)
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5
Q

Why is spectrum important for Aminoglycosides?

A

Aminoglycosides REQUIRE OXYGEN to penetrate bacteria

-ineffective in colon, abscesses, dental pockets

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6
Q

Bactericidal Drugs

A
  1. Aminoglycosides
  2. Penicillins
  3. Quinilones
  4. Cephalosporins
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7
Q

How is it that an antimicrobial drug can be both bactericidal and bacteriostatic?

A
  1. Concentration dependent
  2. Time dependent
  3. Dependent on active replication
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8
Q

Characteristics of Bacteriostatic drugs

  • Onset of activity
  • will immunocompromised patient respond
A
  • take longer to have an effect
  • Rely on intact immune system
  • contra-indicated in immunocomprimised patients
  • –high dose corticosteroids
  • –immunosuppressant drugs
  • –FeLV/FIV
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9
Q

Bacteriostatic Drugs

A
  1. Tetracyclines
  2. Sulfonamides (“sulfas”)
  3. Macrolides
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10
Q

How does action against a bacterial cell wall actually result in the death of the bacterium?
&
What 3 groups of antimicrobial drugs act primarily by disrupting bacterial cell wall formation?

A
  • target enzymes used for cell wall synth –> weakens cell wall –> wall unable to hold bacterium –> bacterial lysis
  • ONLY effective during cell wall FORMATION!
  1. Penicilins
  2. Cephalosporins
  3. Bacitracin
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11
Q

How does a drug that targets the bacteria cell membrane result in the death of the bacterium?

Why do these have more side effects?
&
Abx targeting Cell membrane

A
  • disruption of membrane –> leak of critical solutes
  • Mammals also have PM’s –> damage to membrane (side effects)
    1. Polymyxin B –Neosporin
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12
Q

What drug group disrupts the replication of bacterial DNA by interfering with DNA gyrase?

A

-disrupt translation of DNA into mRNA
OR
-interfere w/ DNA replication (quinolones)

  1. Quinolones
  2. Metronidazole (anaerobic and protozoa)
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13
Q

What metabolic process do sulfonamide (sulfa) drugs target in the bacteria?

Are sulfonamides considered to be –cidal or –static by themselves?

What is trimethoprim, how does it work, and what effect does it have when combined with sulfonamides?

A
  • binds to enzyme needed for essential metabolites (ex Folate)
  • Bacteriostatic effects
  • if combo w/ TriMethoPrim (inhibits another step in the pathway) –> bactericidal
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14
Q

What determines the sensitivity/resistance of bacterial infection

A

Drug conc needed to be effective & ability of host to tolerate that conc.

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15
Q

What metabolic process do sulfonamide (sulfa) drugs target in the bacteria?

Are sulfonamides considered to be –cidal or –static by themselves?

What is trimethoprim, how does it work, and what effect does it have when combined with sulfonamides?

A
  • binds to enzyme needed for essential metabolites (ex Folate)
  • Bacteriostatic effects
  • if combo w/ TriMethoPrim (inhibits another step in the pathway) –> bactericidal
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16
Q

3 requirements for Abx to work

A
  1. must reach location of organism (ADME)
  2. Achieve high enough concentrations to produce effect and persist long enough at the site
  3. Host animal has to be able to tolerate the drug at effective dose
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17
Q

Breakpoints

A

-MIC of bacteria that indicates the drug is effective (s), ineffective (r), may or may not be effective (I)

  1. Culture bacteria from infection
  2. Inoculated diff conc of Abx to determine MIC
  3. Compare MIC to drugs “breakpoint” chart to determine if Resistant, susceptible or intermediate
  • these numbers are based on how much drugs SHOULD be achieved at infection site
  • -MUST consider location of drugs to reach
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18
Q

Wild bacteria

A

-live in environments where they have NOT been previously challenged by abx

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19
Q

Abx considered bactericidal if…

A

MBC (min bactericidal conc) is

<4x MIC (min inhibitory conc)

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20
Q

Non-wild bacteria

A
  • HAVE been exposed to abx –> differenct susceptibility than wild
  • typically harder to kill
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21
Q

Intrinsic resistance

A

Naturally existing resistant mechanism –Normal make up of bacteria
-anaerobic bacteria = natural resistant to aminoglycosides (O2-dependent transport mech)

22
Q

Acquired resistance

A

modification of bacterial genome in a single cell

  • creates a resistant subpopulation
  • gene transfer
23
Q

Vertical gene transfer

A

evolution–pass genetic material to daughter cells

24
Q

Horizontal/ lateral gene transfer

A

transfer of DNA packets btwn same/diff species

  1. conjugation
  2. transformation
  3. transduction
25
Q

Conjugation

A

direct cellular contact & plasmid exchange

–most common mechanism

26
Q

Transformation

A

picks up environmental DNA (from lysed bacteria)

-incorporates into own DNA

27
Q

Transduction

A

Species-specific bacterial virus

-BACTERIOPHAGE transfer DNA btwn closely related bacteria

28
Q

What are the four mechanisms by which resistance occurs in bacteria?

A
  1. Increased porin selectivity (cant enter) -Penicillin
  2. Efflux pump (expulsion) -quinolones
  3. Inactivation (Beta-lactamse) -penicillin and cyclosporins
  4. Modify target site (DNA gyrase) -quinolones
29
Q

Biological resistance VS Clinical resistance

A

Biological- occurring all the time, but not apparent clinical resistance

Clinical - sufficient percentage of a population of one bacterial species has become resistant to a particular Abx

30
Q

What are the four “quadrants” regarding spectrum of activity of a drug?

Give an example of how knowing whether a bacteria exists in the aerobic vs anaerobic quadrant can help determine the selection of an antimicrobial drug.

A 
Gram +        |   Gram +
Aerobe         | Anaerobe 
\_\_\_\_\_\_\_\_\_\_\_|\_\_\_\_\_\_\_\_\_\_\_
Gram -        |   Gram -
Aerobes      | Anaerobes
31
Q

AMINOGLYCOSIDES: Bacteriocidal or static?

A
  • BacteriCIDAL
32
Q

CEPHALOSPORINS: Bacteriocidal or static?

A
  • BacteriCIDAL
33
Q

MACROLIDES: Bacteriocidal or static?

A
  • BacterioSTATIC
34
Q

PENICILLINS: Bacteriocidal or static?

A
  • BacteriCIDAL
35
Q

QUINOLONES (FLUOROQUINOLONES): Bacteriocidal or static?

A
  • BacteriCIDAL
36
Q

SULFONAMIDES (“SULFAS”): Bacteriocidal or static?

A
  • BacterioSTATIC
37
Q

TETRACYCLINES: Bacteriocidal or static?

A
  • BacterioSTATIC
38
Q

Why must drugs that disrupt cell wall formation be given such that they have significant concentrations at the infection site for most of the dosage interval (time between doses)?

A

Bc drug must be present during replication!

39
Q

What drug works by forming unstable bacterial DNA only in anaerobic bacteria and protozoa?

A
  • metronidazole
40
Q

Why do MICs by themselves not give the whole picture about whether or not a particular antimicrobial could be effective against a particular bacterium?

A

It is important to know:
- the toxic level (MTD) to determine if the bacteria is sensitive

  • the MBC to determine if the bacteria is -CIDAL
    (MBC <4x MIC)
41
Q

Why is it that Gram negative bacteria are typically resistant to most penicillin drugs?

A
  • penicillin blocked by Gram negative outer capsule membrane porin
42
Q

Why are Staphylococcus aureus bacteria resistant to fluoroquinolones (“quinolones”) like enrofloxacin (Bayril®)?

What is the mechanism by which Staphylococcus aureus bacteria is resistant to penicillin and cephalosporins?

A
  • rapidly mutate their efflux pump to pump drug out.
43
Q

gentamicin and amikacin are…

A

Aminoglycosides

44
Q

beta lactam drugs are…

A

penicillins and cephalosporins

45
Q

Enrofloxacin is..

A

Baytril®, which is a quinolone.

46
Q

Trimethoprim makes …

A

Sulfas bactericidal

47
Q

AMR

A

Antimicrobial resistance

48
Q

Another name for Antifungal

A

antimycotic

49
Q

MIC

A

Minimum inhibitory concentration

50
Q

MBC

A

Minimum bacteriocidal concentration

51
Q

MTD

A

Minimum toxic dose

52
Q

To reduce selection pressure

A
  1. appropriate dose
  2. long enough
  3. educate O’s about tx regimen
  4. Abx for bacterial infection only
  5. know Ps immune status

Pharm Exam 1 (6 decks)

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