Antibiotics and Anti-fungals Flashcards
Describe the distinctive features of:
a. Gram positive bacteria
b. Gram negative bacteria
c. Mycolic bacteria
a. Gram positive bacteria Thick peptidoglycan cell wall b. Gram negative bacteria Outer membrane that contains lipopolysaccharide (LPS) c. Mycolic bacteria Outer mycolic acid layer
State the steps involved in the production of THF from PABA.
PABA –> DHOp (enzyme = dihydropterase synthase)
DHOp –> DHF
DHF –> THF (enzyme = DHF reductase)
What is DNA gyrase?
A type of topoisomerase (topoisomerase II)
It releases tension in DNA and is important in unwinding DNA to allow protein binding required for DNA replication
What does RNA polymerase do?
Produces RNA from a DNA template
What is the key difference between ribosomes in eukaryotes and prokaryotes?
Eukaryote = 40S + 60S Prokaryote = 30S + 50S
State two classes of drugs that interfere with nucleic acid synthesis and name the enzymes that they inhibit.
Sulphonamides – inhibits dihydropterate synthase
Trimethoprim – inhibits DHF reductase
These two drugs are sometimes used together. What is this preparation called?
Co-trimoxazole
Name a group of drugs that interfere with DNA replication and state its targets.
Fluoroquinolones (e.g. ciprofloxacin) inhibits bacterial DNA gyrase and topoisomerase IV
Name a group of drugs that interfere with RNA synthesis and state its main target.
Rifamycins (e.g. rifampicin) – inhibits RNA polymerase
List 4 groups of drugs that interfere with ribosomes.
Macrolides
Chloramphenicol
Aminoglycosides
Tetracyclines
Describe how peptidoglycan is synthesized, transported to the cell wall and incorporated into the cell wall.
A pentapeptide is created on N-acetyl muramic acid (NAM)
N-acetyl glucosamine (NAG) associates with NAM forming peptidoglycan
The peptidoglycan is then transported into the cell wall by bactoprenol
The peptidoglycan is then incorporated into the cell wall by transpeptidase enzyme, which cross-links the peptidoglycan pentapeptides
Which groups of drugs interfere with peptidoglycan synthesis and how do they do this?
Glycopeptides (e.g. vancomycin) – they bind to the pentapeptides and inhibit peptidoglycan synthesis
This is used as a last resort for Gram-positive bacteria that are resistant to other antibiotics
Name a drug that interferes with peptidoglycan transport andstate its target.
Bacitracin – this inhibits bactoprenol, hence preventing peptidoglycan transport
Name a class of drugs that inhibit peptidoglycan incorporation and explain how they do this.
Beta lactams – they bind covalently to transpeptidase, which inhibits peptidoglycan incorporation into the cell wall
What are the three subsets of beta lactams?
Carbapenems
Cephalosporins
Penicillins