Lecture 15 Flashcards
(31 cards)
When was the penicillin mould first discovered?
1929
When was penecillin first widely used?
1940s
What bacterical cell structure is targeted in penecillins?
The cell wall. as the antibiotic prevents proper formation of this strucure resulting in the cell being unable to resist osmotic pressure, resulting in lysis
What does MRSA stand for?
Methicillin resistant staphylococcus aureus
What part of the bacterial cell wall structure is specifically inhibited by penecillin-based antibiotics?
The transpeptide links between individual sugar strands
What alternating sugar monomers make up a peptidoglycan thread?
N-acetylmuramic acid and N-acetyl-glucosamine
Which enzyme does penecillin act on and how?
Penecillin acts as a competitive inhibitor, through its beta-lactam ring for the transpeptidase enzyme which forms cross links between peptidoglycan strands preventing it from binding to the terminal alanine
How many R chains are seen in penicillin?
One
How many R chains are seen in Cephalosporins?
two
What are the R chains on penecillin and cephalosporin used for in semi-synthetic anti-biotics?
To modfiy the properties of the antibiotic to work against antibiotic resistance
What are the two types of resistance to penicillin antibiotics?
Beta-lactamase enzyme,
Variant in the transpeptidase enzyme
How does betalactamase resistance work?
Enzyme which cuts the beta-lactam ring resulting in inactivation of the antibiotic
How does transpeptidase resistance work?
The bacteria uses a transpeptidase enzyme which has a different structure so it is not affected by penicillin
What is the ‘original’ penicillin?
benzylpenicillin
What is cloxacillin?
A semi-synthetic antibiotic, resistant to beta lactamase S.Aureus
What is Flucloxacillin?
A penicillin which is absorbed orally as it is more stable
Which semi-synthetic penicillin based antibiotic causes kidney damage?
Methicillin
How do semi-synthetic antibiotics such as Cloxacillin and Flucloxacillin prevent beta-lactamase resistance?
The larger R groups prevent beta lactamase from accessing the beta lactam bond while still allowing access to transpeptidase
What is another name for S.Aureus that has resistance through a different transpeptidase?
MRSA (Methicillin Resistant S.Aureus)
What is the current method of dealing with MRSA as it increases in frequency?
Use the non-beta-lactam antibiotic, vancoymycin
What antibacterial resistance to penicillin does S.pyogenes have?
None to penicillin, still 100% susceptible
What does anti-bacterial resistance does Neisseria Gonorrhoea have?
Both transpeptidase and beta-lactamase
What antibiotic resistance does S.Pneumonia have?
Transpeptidase resistance but no beta-lactamase resistance
What is Penicillin G?
The original benzyl-penicillin
