Flashcards in antibiotics med chem Deck (97)
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1
mutualistic relationship
both organisms benefit
2
opportunistic relationship
under normal conditions the microbe does not cause disease, but can if certain conditions are met
3
features of gram positive bacteria
-Outer peptidoglycan layer
-stains purple
4
features of gram negative bacteria
-out lipopolysaccharide layer
-porins provide channels through LPS
-stains pink
5
antibiotics that are from manmade sources
sulfa drugs
fluoroquinolones
linezolid
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bacteriocidal
kills bacteria
(technically all antibiotics are bacteriocidal at high doses)
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bacteriostatic
inhibits growth of bacteria
8
sugar with the peptide attached for cross linking in peptidoglycan
NAM
9
amino acids needed to form cross-link
-D-Ala D-Ala on NAM
-pentaglycine chains linking the NAMs
10
steps of forming peptidoglycan cross-link
in cytoplasm
1. synthesize NAM
2. attach NAG and prenyl
3. add peptide side chain
4. flipping into periplasm
in periplasm
5. form crosslink
11
enzyme that makes crosslinks
transpeptidase
12
what facilitates transport of NAG and NAM into periplasm
bactoprenol
13
how does transpeptidation take place?
1. penicillin binding protein has an active Ser that attacks the non-terminal D-Ala forming an ester bond
2. Ester bond can be attacked by an amine in the pentaglycine chain via transpeptidation, forming a cross link
14
beta-lactam MoA
mimic D-Ala D-Ala to form a bond with PBP and prevent it from being used to make cross links, thus opening the cells wall
15
definition of a lactam ring
an intramolecular ring with an amine and a carboxylic acid linked with varying amounts of carbons (alpha=1, beta=2, and so on)
16
what part of beta-lactams mimics the D-Ala D-Ala peptide
the acidic withdrawing group on the lactam ring
17
Problems with beta lactams
-degraded by water and stomach acid due to its instability
-resistance via beta-lactamase, penicillinase, and other mechanisms
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beta-lactamase function
hydrolysis of penicillins
19
location of beta-lactamase in gram positive bacteria
outside the peptidoglycan
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location of beta-lactamase in gram negative bacteria
periplasmic space, between LPS and cytoplasmic membraine
21
general SAR of penicillins
-required S in ring
-ring system
-no substitution on ring
-"west end" has amide linkage
-aromatic or cyclic function in "west end" R group
-dimethyl on east end
22
penicillin G features
-early penicillin
-very Gm+ (no staph)
-little Gm-
-unstable when given orally
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penicillin V features
-early penicillin
-very Gm+ (no staph)
-little Gm-
-given orally b/c of ether electron withdrawing group
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early penicillins
Pen G
Pen V
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methicillin features
-ortho groups prevent beta-lactamase attack
-ok GM+
-little GM-
-given IV
26
nafcillin features
-ortho groups prevent beta-lactamase attack
-ok GM+ (staph)
-little GM-
-given IV
27
oxacillins feature
-ortho groups prevent beta-lactamase attack
-ok GM+ (staph)
-little GM-
-given oral
28
penicillinase-resistant penicillins
-methicillin
-nafcillin
-oxacillins (oxacillin, cloxacillin, dicloxacillin)
29
ampicillin/amoxicillin features
-amino group good for passing through porins
-good Gm-
-good Gm+
-good substrate for beta-lactamase
-ineffective against pseudomonas
-given orally
30
