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Antibiotics 2 Flashcards

1
Q

what does penicillin inhibit?

A

PBP

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2
Q

what is the chemical structure of a NAM subunit?

A

peptide side chains with 1 proximal L-alanine and 2 distal D-alanines

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3
Q

what does PBP do?

A

binds peptide side chains to form a cross link with the removal of 1 D-alanine

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4
Q

how does penicillin inhibit PBP?

A

enters the active site of PBP and reacts with the serine group which is important for activity

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5
Q

how does penicillin permanently block the active site of PBP?

A

the beta lactam ring of the penicillin is opened and it remains covalently linked to PBP

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6
Q

what bacteria does penicillin treat?

A

strep and staph, Neisseria, anaerobes, spirochetes

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7
Q

what are the pharmacokinetics of penicillin G?

A

acid labile, widely distributed, rapid renal excretion

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8
Q

how are some bacteria resistant to penicillin?

A

does not pass gram negative cell envelope very well and degraded by beta lactase enzymes

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9
Q

what are beta lactamase enzymes?

A

produced by bacteria and provide resistance to beta lactam antibiotics

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10
Q

how does beta lactam enzymes degrade beta lactam antibiotics?

A

break open the lactam ring via hydrolysis

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11
Q

what antibiotics are penicillinase resistant?

A

methicillin and oxacillin

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12
Q

what antibiotics have a broad spectrum?

A

amoxicillin and ampicillin

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13
Q

what antibiotics are antipseudomonas?

A

azlocillin and piperacillin

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14
Q

how is penicillin G administered?

A

requires injection

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15
Q

how is penicillin V administered?

A

can be taken orally

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16
Q

what are the natural penicillins?

A

pen V and pen G

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17
Q

what are the semisynthetic penicillins?

A

oxacillin and ampicillin

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18
Q

what are the clinical uses of penicillins?

A

pneumonia, meningitis, staph infections, syphilis, urinary tract infections

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19
Q

what are the adverse reactions to penicillins?

A

hypersensitivity, immediate anaphylaxis

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20
Q

what is augmentin?

A

combination of clavulanic acid and amoxycillin

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21
Q

what does clavulanic acid do?

A

acts as a beta lactam inhibitor

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22
Q

what is the mechanism fo augmentin?

A

acts as a competitive and reversible inhibitor of beta lactamase enzymes

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23
Q

what are the adverse reactions of cephalosporins?

A

hypersensitivity, thrombophlebitis and nephrotoxicity

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24
Q

how are cephalosporin variants produced?

A

modification of the side chain at position 7 and substituents on position 2 of the ring

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25
what are the first generations of cephalosporins?
cephalosporin, cephalexin, cephradine
26
how are second generations of cephalosporins produced?
removal of methyl group
27
what are the second generation cephalosporins?
cefaclor and cefuroxime
28
how are third generation cephalosporins produced?
R1 and R2 groups changed ao that it is stable without refrigeration
29
what are the third generation cephalosporins?
cefotaxime and ceftriaxone
30
what are the most active cephalosporins against E.coli?
third generation
31
what cephalosporins have increased activity against pseudomonas aeruginosa?
third generation
32
what does third generation cephalosporins have decreased activity against?
gram-positive staphylococci
33
what are the fourth generation cephalosporins?
cefepime and cefipriome
34
how is a fourth generation cephalosporin created?
quaternary N-methyl pyrrolidine (NMP) at R1
35
what is different about fourth generation cephalosporins?
improved resistance to beta lactamase and penetration of outer membrane of gram negative bacteria, extended spectrum
36
what causes fourth generation cephalosporins to have minimal beta lactamase activity?
rapid periplasmic penetration and high PBP access
37
what drug resistant bacteria is fourth gen cephalosporins effective against?
enterobacter and klebsiella
38
what does isoniazid do?
inhibits cell wall synthesis due to no mycelia acid synthesis
39
what is mycolic acid?
alpha-alkyl-beta-hydroxy long chain fatty acids
40
how can resistance to isoniazid occur?
mycobacterial enzyme called peroxidase so depletion of peroxidase causes resistance
41
how are neuropathic side effects of isoniazid ameliorated?
by co-administration of B6
42
how does isoniazid lead to blocked fatty acid synthesis?
activated by KatG which catalyses the formation of INH-NAD complex, which then binds tightly to enoyl-aceyl carrier protein reductase which becomes inactive so no fatty acid synthesis
43
how does blocked fatty acid synthesis lead to a damaged cell wall?
no mycolic acid synthesis
44
what is rifampicin used to treat?
mycobacterium infections including tuberculosis and leprosy
45
how does rifampicin inhibit RNA synthesis?
inhibits the bacterial dependant RNA polymerase
46
what 3 drugs cause inhibition of protein synthesis?
chloramphenicol, tetracycline and streptomycin
47
how does chloramphenicol work?
binds to the 50s subunit and inhibits formation of peptide bond
48
how does tetracycline work?
interfere with attachment of tRNA to the mRNA-ribosome complex
49
how does streptomycin work?
changes shape of the 30s subunit, causing the mRNA to be read incorrectly
50
how are drugs that inhibit protein synthesis achieve selective toxicity?
due to translational events differing in eukaryotes and prokaryotes
51
how large are eukaryotic and prokaryotic ribosomes?
eukaryotic = 80s and prokaryotic = 70s
52
what antibiotics act on 50s subunits?
chloramphenicol, lincosamides, erythromycin and fusidic acid
53
what are the 2 subunits of a prokaryotic ribosome?
50s and 30s
54
what antibiotics act on the 30s subunit?
ahminoglycosides and tetracyclines
55
what is the target for ahminoglycosides?
fmet binding and initiation complex
56
what is an example of an amino glycoside?
streptomycin
57
what is the target of tetracycline?
binding of tRNA to the available aminoacyl site on the 50s subunit
58
what is the target for chloramphenicol and lincosamide?
the formation of a peptide bond
59
what is the target for erythromycin?
translocation of peptidyl tRNA so removal of tRNA molecule prevented
60
why might erythromycin be prescribed?
when someone is allergic to penicillin
61
what does sulfamindes and trimethoprim do?
prevents formation of pyrimidine and purine
62
what drugs are inhibitors of DNA replication? how?
quinolone as prevent action of DNA gyrase
63
what drugs are inhibitors of RNA polymerase? how?
rifampicin as prevents RNA synthesis
64
what are the 4 types of antiviral inhibitors?
protease inhibitors, entry inhibitors, reverse transcriptase inhibitors and non-nucleotide reverse transcriptase inhibitors
65
what type of inhibitor is acyclovir?
nucleoside reverse transcriptase inhibitors
66
how is acyclovir prodrug action increased?
after metabolisation, acyclovir-GTP has 100x higher affinity for viral polymerase
67
how does acyclovir prevent viral replication?
incorporation into viral DNA causes premature chain termination
68
what is target site alteration?
the target site is altered by reducing the affinity for the antibiotic without impairing cellular function
69
what is the two types of target site alteration?
cell wall synthesis and protein synthesis
70
how is target site altered in cell wall synthesis?
shift in amino acid sequence in PBP reduces the affinity for penicillin
71
how is target site altered in protein synthesis?
shifts in amino acid sequence of ribosomal proteins reduces the affinity for erythromycin and tetracycline
72
how is the access to target site modified to gain antibiotic resistance?
ability of antibiotic to enter bacterial cell and gain access to target site is impaired
73
what are the mechanisms of antibiotic resistance?
target site modification, access to target site modified, inactivation of antibiotic and efflux
74
how does the cell wall lead to resistance in terms of access to target site being modified?
alterations of the composition of bacterial membrane can reduce permeability for antibiotic
75
what is inactivation of antibiotic?
antibiotics is inactivated by enzymes produced by bacteria
76
how is cell wall synthesis involved in inactivation of antibiotic?
beta lactamase inactivates penicillin by catalysing lactam ring cleavage
77
how is protein synthesis involved in inactivating an antibiotic?
amino glycoside modifying enzymes and chloramphenicol transferases prevent disruption of protein synthesis by modifying the structure of the antibiotic
78
what is efflux?
the antibiotic enters the bacteria but rapid expulsion lowers the cytoplasmic concentration

Principles of Pharmacology (12 decks)

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