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Pharmacology Test 3 > Antibiotic Agents Targeting Bacterial Cell Wall Synthesis > Flashcards

Antibiotic Agents Targeting Bacterial Cell Wall Synthesis Flashcards

1
Q

Gram + Bacteria

A

3 layers of peptidoglycan

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2
Q

Gram - Bacteria

A
  • outer membrane
  • – makes more difficult to enter bacteria
  • – drugs need to be SMALL/hydrophilic
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3
Q

Broad Spectrum

A
  • work against both classes of bacteria
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4
Q

Extended Spectrum

A
  • drug whose selectivity is broadened by chemical modification
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5
Q

Edge of Life

A
  • choose broad spec drug to start; figure out what type of bacteria later
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6
Q

Chemical Constituents of Peptidoglycan Later

A
  • NAG
  • NAM
  • sugars crosslinked
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7
Q

Cell wall agents block proper assembly of peptidoglycan later

A
  • D alanine released every time cross-linking occurs
  • transglycosylase enzymes link sugars together
  • transpeptidase enzymes join sugar-linked peptides to x-link polysaccharide chains
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8
Q

B-lactam Antibiotics

A

Penicillin mimics D-Ala-D-Ala, the last two amino acids of the peptide bridge precursor

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9
Q

Mechanism of B-Lactam

A
  • transpeptidase active site = serine
  • – serine attacks peptide bond (D-Ala breaks off/released)
  • –enzyme linked to peptide
  • – glycine from another unit attacks remaining D-Ala-enzyme bond => peptidogylcan crosslink
  • — enzyme released to carry out rxn over & over again

WITH DRUG
** enzyme binds to drug thinking its D-Ala-D-Ala and enzyme now covalently linked to drug =. CANT BE TAKEN BACK OFF = STUCK **

  • kills actively growing cells (bactericidal)
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10
Q

Bacteria B-lactamases

A
  • bacteria enzyme which hydrolyzes B-lactam antibiotics
  • H2O can break enzyme OFF so it can continue working/growing (hydrolyze serine-lactam linkage)
  • can be transferred from organism to organism
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11
Q

Penicillin binding proteins (PBP)

A

DD-transpeptidases and B-lactamases

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12
Q

B-lactamase inhibitors

overview

A
  • don’t kill bacteria
  • destroy enzyme preventing killer drug from killing the bacteria
  • pharmacologist’s response to B-lactamases
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13
Q

B-Lactamase Inhibitors

A
  • combined with B-lactam antibiotics to extend their t1/2

- bind B-lactamases covalently and inactivate IRREVERSIBLY

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14
Q

Amoxicillin

Penicillin

A
  • acid stable
  • greater activity against gram - because of their ability to penetrate outer membrane
  • inactivated by lactamases

Augmentin: amoxicillin + calvulanate (B-lactamase inhibitor)

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15
Q

Penicillin

Routes of adminitration

A
  • oral
  • IV
  • IM
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16
Q

Penicillin

Route of elimination

A
  • rapid active secretion
  • 80% of dost cleared in 3-4 hours after administration
  • can cause renal failure
  • cross reactive: allergies
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17
Q

Penicillin

Resistance

A

1) upregulation of chromosomally-encoded B-lactamases
2) acquisition of B-lactamases by horizonal gene transfer from other bacteria
3) mutation of primary penicillin binding proteins (MRSA)

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18
Q

MRSA

A

methicillin-resistant staphy aureas

19
Q

Clavulanic Acid

A

B-lactamase inhibitor

20
Q

Cephalosporins

A
  • broader spectrum due to increased resistance to B-lactamases
  • 3rd gen + great if patient is allergic to penicillin
21
Q

3rd Gen Cephalosporins

A
  • extended gram - activity at the expensive of gram +
  • some cross blood-brain barrier
  • effective against inducible B-lactamase-production but not constitutive B-lactamas-producing strains
  • ** no allergic cross reactivity with penicillin ***
22
Q

Cephalosporins
route of administration
route of elimination

A
  • admin: oral, IV

- elim: kidney: can build up to toxic levels

23
Q

Ciferodocol

Cephalosporin

A
  • B-lactamase resistant cephalosporin with high permeability to gram -
  • no activity against gram +
24
Q

Ciferodocol Mechanism

Cephalosporin

A
  • side chain mimics siderophores (help pull in iron)
  • act as trojan horse
  • iron intake system brings in drug to bacteria = bypasses cell wall)
25
Q

Alternatives for those allergic to penicillin

A
  • monobactams

- cephalosporins

26
Q

Monobactams

A
  • relatively resistant to B-lactamases
  • active against gram - rods
  • no activity toward gram +
  • – drug does not bind transpeptidases of gram + or anerobic bacteria
  • ** no cross reactivity with penicillin ***
27
Q

Aztreonam

A

Monobactam

28
Q

Carbapenems

A
  • broad spec
  • good activity against many gram - rods, gram + bacteria, and anaerobes
  • used for mixed infections
  • resistant to some serine B-lactamases; packaged with B-lactamase inhibitors
  • penetrate CNS
  • ** cross sensitivity to penicillin ***
29
Q

Impenem

A

Carbapenems

  • inactivated by dehydropeptidases in renal tubes
  • – Cilastatin (renal dehydropeptidase inhibitor) increases t1/2
30
Q

Ortavancin

A
  • semisynthetic glycopeptide derived from vancomycin
  • comparable efficacy to vancomycin
  • effective for skin infections by methicillin-resistant gram + bacteria
  • ** long t1/2 permits SINGLE DOSING and outpatient care ***
31
Q

Oritvancin type

A

non-B-lactam cell wall synthesis inhibitors

32
Q

Oritvancin mechanism

A
  • makes incredibly tight bond to D-Ala-D-Ala

- – can’t get to it to continue construction

33
Q

Oritvancin Route of Elimination

A

Gram +

- kidney

34
Q

Oritvancin Tissue distribution

A
  • good including brain
35
Q

Daptomycin

A
  • bacteria cell membrane pore former
  • kills bacteria via K+ leak
  • ** Kills WITHOUT rupturing ***
  • approved from gram + skin and soft tissue infections that involve MRSA
36
Q

Polymyxins

A

GRAM - ONLY

  • bind outer membrane leading to permeability of both inner and outer membranes: PERFORATIONS (spill innards)
  • binds a lipopolysaccharide molecule specific to outer membranes of Gram -, thus no gram +
37
Q

Polymyxins Resistance

A
  • occurs via changes in lipopolysaccharide structure of outer membrane
38
Q

Polymyxins Administration

A

usually topical, can be IV

39
Q

Fosfomycin

A

CANT MAKE ANY NAM
- drug inhibits first committed step in cell wall synthesis: conversion NAG -> NAM
- drug binds covalently to active site cysteine of MurA enzyme
- oral admin
SAFE in PREGNANCY

40
Q

Fosfomycin Resistance

A
  • attributed to loss of drug transport into cell

- MurA of TB is NATURALLY RESISTANT

41
Q

Fosfomycin Elimination

A

excreted by kidney

42
Q

Fosfomycin Utility

A
  • active against gram + and gram -
  • synergistic when combined with other antibiotics
  • used for uncomplicated UTIs
43
Q

Bacitracin

A
  • cyclic polypeptide active against gram +
  • inhibits lipid phosphatase that dephosphorylates lipid carrier of peptidoglycan subunits
  • ONLY topical: v. dangerous to kidney
  • usually combined with other antibiotics
  • allergic reaction possible
44
Q

D-cycloserine

A
  • V TOXIC
  • only used last resort for TB
  • competitively inhibits alanine racemase and D-alanine ligase
  • used in combination
  • very serious side effects including CNS

Pharmacology Test 3 (9 decks)

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