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50 Cards in this Set
- Front
- Back
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What are the 2 residues involved in cross linking of the peptidoglycan cell wall?
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lysine
meso-diaminopimelioc acid |
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What are the stages of peptidoglycan synthesis and where do they occur?
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Assembly of PG precurssors - cytoplasm
transport to periplasm - membrane synth of PG polymer - periplasm |
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What is on the C-term of the polypeptide in PG?
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D-ala D-ala
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What are the 4 classes of B-lactam antibiotics?
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Penicillin
Cephalosporin Carbapanem Monobactam |
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What is the structure of cephalosporins?
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b-lactam ring fused with a 6 member ring
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What are the R-groups sites of modification in cephalosporins?
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1. b-lactamase
2. amidase 3. esterase |
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What does b-lactamase do in cephalosporin?
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C-N inactivation
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What does amidase modification do in cephalosporin?
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R1 modification
activity against grm +/- b-lactimase resistance |
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What does esterase modification do in cephalosporins?
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R2 modification
half life of the drug in vivo |
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Mechanism of transpeptidation is inhibited by?
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b-lactam antibiotics
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How do b-lactam antibiotics inhibit transpeptidation?
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inactivates both enzymes for coavalent cross liniking
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What does decreased permeability to a drug do?
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RESISTANCE
mutation in outer memb protiens ie porins is non-specific resistance |
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What does mutation of penicillin binding protiens do?
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increased resistance to drung
ie. strep pneumoniae |
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What happens when bacteria aquire new DNA that cataylze drug inactivation?
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cleavage of b-lactam ring is common due to the action of b-lactimase
often accompanied by resistance to other drugs |
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What does cycloserine do?
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inhibits peptidoglycan synth
cell wall inhibitor |
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What is the structure of cycloserine?
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like D-ala
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How ddoes cycloserine work?
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competitive inhibitor of D-ala in to sequetional rxns
1. alanine racemase 2. d-ala d-ala synthase |
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What does vancomycin do?
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blocks cross linking of PG
bactericidal |
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What is vancoymcin's mech of action?
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complexes with D-ala
prevents crosslinking |
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What does vancoymcin work against?
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Gram +
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When do we use vancomycin?
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with penicillin resistance or cephalosporin hypersensitivity
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What is vancomycin used to treat?
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infection by MRSA (Methocillin Resistant Staph Aureus)
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What does bacitracin do?
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polypetide that blocks PG biosyth by binding the lipid carrier & preventing it from recycling
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What are some reasons cell wall inhibitors are clinically useful?
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high selectivity
low toxicity to the host active against growing bacteria |
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What type of ribosomes do prokaryotes have?
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70S (50 and 30 subunits)
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What does tetracyclines do?
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bind to P residues on 30S subunit adn interferes with binding of aminoacyl t-RNA to the ribosome
*bacteriostatic |
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For who is tetracycline active?
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BOTH eu and pro
but we deal with them differnetly |
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How do prokaryotes deal with tetracyclines?
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E-dependent transporst that takes it up and it accumulates in the cell causing death
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What are 2 ways prokaryotes have developed resistance to tetracycline?
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1. actively pumps it out
2. resistant ribosomes |
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How do aminoglycosides work?
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inhibit formation of the 30S initiation complex to decrease the rt of protien synth
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What are 2 aminoglycosides?
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kanamycin
gentamicin |
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What is the main problem with aminoglycosides?
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limited perm across the outer memb
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How do we overcome the main problem with aminoglycosides?
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use in combo with b-lactams that disrupt PG to allow more efficient entry of aminoglycosides
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How have bacteria formed resistance against aminoglycosides?
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covalent modification preventing efficient transport into the bacteria
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How do Erthyromycin macrolides work?
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binds the 50S ribosome to inhibit its release of deaminoacyl tRNA and inhibits the translocation of peptides
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How has resistance to erythromycin come about?
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some bacteria can methylate rRNA and erthyromycin cannot bind the methylated rRNA
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What type of action does erythromycin have?
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bacteriostatic unless at high concentrations then it is bacteriocidal
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What is Metronidazole?
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inhibitor of DNA which produces radicals to damage DNA used to tx anaerobic bacteria infections
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What is the mech of action of Nalidixic acid?
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synthetic quinoline that selectively inhibits bacterial DNA gyrase
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What is the advatnage to fluorinated quilone (cypro)?
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more active than nalidixic acid to inhibit bacterial DNA gyrase
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What can cause resistance to quilones?
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pt mutation in bacterial DNA gyrase makes it unrecognizable
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What is tetrahydorfolate biosythesis?
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2 enzyme pathway
used to introduce single Cs into biosynthetic precussors |
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What 2 drugs block tetrahydorfolate biosynthesis?
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Sulfonamides
Trimthoprim |
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What is the mech of action of sulfomides?
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inhibits dihydrofolate synthase as a competitive inhibitor to pABA
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Why do sulfonamides work?
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synthase is unique to bacteria and animals require folic acid for growth
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What is the mech of action of trimthoprim?
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inhibits dihydrofolate reductase
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What is an example of synergy where 2 drugs act to sequentially block a metab pathway?
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sulfonamides and trimethoprim
folic acid biosythesis |
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What is an example of synergy where 1 drug enhances the uptake of another drug?
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penicllin and aminoglycosides
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What is an example of synergy where 1 drug may prevent the inactivation of another drug?
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clavulanic acid inactivates b-lactimase to increase the activity of b-lactam
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What is the new drug that inhibits translation and therefore protein synth?
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linezolid
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