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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
Alternatives for those allergic to penicillin
- monobactams | - cephalosporins
26
Monobactams
- 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
Aztreonam
Monobactam
28
Carbapenems
- 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
Impenem
Carbapenems - inactivated by dehydropeptidases in renal tubes - -- Cilastatin (renal dehydropeptidase inhibitor) increases t1/2
30
Ortavancin
- 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
Oritvancin type
non-B-lactam cell wall synthesis inhibitors
32
Oritvancin mechanism
- makes incredibly tight bond to D-Ala-D-Ala | - -- can't get to it to continue construction
33
Oritvancin Route of Elimination
Gram + | - kidney
34
Oritvancin Tissue distribution
- good including brain
35
Daptomycin
- 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
Polymyxins
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
Polymyxins Resistance
- occurs via changes in lipopolysaccharide structure of outer membrane
38
Polymyxins Administration
usually topical, can be IV
39
Fosfomycin
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
Fosfomycin Resistance
- attributed to loss of drug transport into cell | - MurA of TB is NATURALLY RESISTANT
41
Fosfomycin Elimination
excreted by kidney
42
Fosfomycin Utility
- active against gram + and gram - - synergistic when combined with other antibiotics - used for uncomplicated UTIs
43
Bacitracin
- 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
D-cycloserine
- 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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