Bacteria III Flashcards
What links the glycan strands together?
Peptide bonds
What are the targets in peptidoglycan synthesis?
Transglycosylation and transpeptidation
What does transglycosylation do?
Polymerises the glycan strands
What does transpeptidation do?
Cross links between glycan strands
What catalyses transpeptidation and transglycosylation?
Penicillin binding proteins
What are the two main agents that interfere with bacterial wall synthesis?
Beta lactams and glycopeptides
What do beta lactams block?
Penicillin binding proteins - block cross-link of the peptide side chains
Are peptidoglycan hydrolyses affected by beta lactams?
No - they continue to hydrolyse PG & this leads to weakening of peptidoglycan especially at the division site. Leads to protrusion of cytoplasmic membrane and osmotic lysis/cell death.
What can occur after beta lactam injection?
Anaphylactic shock
What do beta lactamases do?
Break down and remove the structural analogity of beta lactams
Have a serine in their AS responsible for catalysis
Zinc have a broader spectrum than serine
What can inhibit beta lactamases?
Clavulin
What is the core structure of penicillin?
6-aminopenicillianic acid - can modify the chemical group to make a range of molecules
What does the nature of the R group determine?
The drugs stability to enzymatic or acidic hydrolysis and affects its antibacterial spectrum
What are the four types of beta lactam?
Penicillins
Cephalosporins - broad spectrum (4th), found in urine, can penetrate into the CSF
Carbapenems
Monobactams
What are the three types of carbapenem?
Imipenem Meropenem Ertapenem Very stable to most serine beta lactamases Kept in reserve
What does vancomycin bind to?
D-ala-D-ala and blocks the subsequent reactions that would take place. Inhibitor of transglycosylation
Can’t penetrate into Gram negative as it is too big for the channels
What does vancomycin treat?
S.Aureus particularly MRSA
Patients that are hypersensitive to penicillin
What targets the membrane?
Polymyxin & colistin - active against gram negative bacteria
What part of the membrane do polymyxin and colistin target?
Lipopolysaccahrides and cause disruption of the IM membrane
Can be used as therapy for cystic fibrosis infections
What is daptomycin?
Targets the membrane and is a cyclic lipopeptide - doesn’t make specific contacts with the lipopolysaccahrides
What does daptomycin need to be present to work?
Calcium ions as you need to stop the repulsion
What can daptomycin be used to treat?
Complicated skin/soft tissue infections
How is daptomycin administered?
IV
What are the adverse side effects of daptomycin?
Muscle toxicity
What are the strands in peptidoglycan?
NAM and NAG
