Bacterial Cell Wall Synthesis Flashcards
What bacterium has more PDC?
Gram positive
What does glycan consist of?
NAG + NAM
Function of PDC?
Maintains shape + mechanical strength of cell wall
What happens if cell wall is damaged?
Cell becomes leaky, swell + cell lysis occurs
Why is the cell wall a target for antibiotics?
Mammalian cells do not have a cell wall + antibiotics show excellent selective toxicity
D-Cycloserine
Antibiotic acts as a structural homologue for D-alanine inhibiting
- RACEMASE converts L-ala to D-ala
- LIGASE joins the D-alanyl-D-alanine dipeptide
D-cycloserine binds to pyroxidoxal phosphate enzyme cofactor
D-cycloserine is used as a SECOND LINE antibiotic in combo. with others
Glycopeptides
Block the binding of D-alanyl-D-alanine dipeptide which prevents binding + function of Transglycosylase
How does antibiotic resistance occur?
When bacteria are able to survive exposure of one or more antibiotics
2 types of antibiotic resistance
Intrinsic and Acquired
What is Intrinsic resistance + how does it occur?
Intrinsic resistance is natural resistance to bacterial species to antibiotics
It occurs naturally by:
(1) LACK OF TARGET - molecular target of the antibiotic are not present within microorganism
(2) LACK OF PERMEABILITY - LPS outer membrane of gram-negative bacterium can prevent antibiotics accessing intracellular target
How does Acquired resistance occur?
Acquired resistance occurs in previously sensitive cells following mutations and transfer of genetic information between cells.
What are the 4 resistance mechanism to antimicrobial agent include?
(1) Drug inactivation
(2) Alteration of the drug target
(3) Reduced cellular target
(4) Increased efflux
Pyogenic (Pus-forming) Toxins
Toxins that cause localised tissue destruction - infected wounds, boils, abscesses
What bacterial toxins cause food-poisoning?
Enterotoxins A-E of S-aureus
Enterotoxins SPE A, SPE, B SPE C of S.pyogenes
Enterotoxins of B.cereus
Enterotoxins tend to be heat stable toxins (resist damage when cooked and ingested) and produced by bacteria contaminating food stuffs
Can produce effects without the bacteria infecting the host i.e. it’s the toxin alone.
Tend to work as emetic toxins, being absorbed by the gut and travelling in the circulation to the ‘vomiting ‘centre in the brain
Onset is rapid (~ few hours)
What are Enterotoxins?
Enterotoxins tend to be heat stable toxins (resist damage when cooked + ingested) and produced by bacteria contaminating food-stuffs
