Antibiotics and Anti-fungals Flashcards
Describe the distinctive features of: Gram positive bacteria, Gram negative bacteria and Mycolic bacteria
Gram +ve bacteria: Thick peptidoglycan cell wall
Gram -ve bacteria: Outer membrane contains lipopolysaccharide (LPS)
Mycolic bacteria: Outer mycolic acid layer
State the steps involved in the production of THF from PABA. What is THF important for ?
PABA –> DHOp (dihydropterase synthase)
DHOp –> DHF
DHF –> THF (DHF reductase)
THF important in nucleic acid synthesis
What is DNA gyrase?
A topoisomerase
Releases tension in DNA + 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 function of ribosomes? What is the key difference between ribosomes in eukaryotes and prokaryotes?
Produce protein from RNA templates
Eukaryote = 40S + 60S
Prokaryote = 30S + 50S
State 2 classes of drugs that interfere with nucleic acid synthesis and name the enzymes that they inhibit.
Sulphonamides: inhibits DHOp synthase
Trimethoprim: inhibits DHF reductase
Sulphonamides and Trimethoprim 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 inhibit bacterial DNA gyrase + topoisomerase IV
Name a group of drugs that interfere with RNA synthesis and state its main target.
Rifamycins inhibits bacterial RNA polymerase
Mainly used in tuberculosis
List 4 groups of drugs that inhibit ribosomes.
Macrolides e.g. Erythromycin
Aminoglycosides e.g. Gentamicin
Chloramphenicol
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
PtG is transported across the membrane by bactoprenol
PtG is incorporated into the cell wall by transpeptidase enzyme, which cross-links PtG pentapeptides
Which groups of drugs interfere with peptidoglycan synthesis and how do they do this?
Glycopeptides (e.g. vancomycin): bind to pentapeptides + inhibit PtG synthesis
= a last resort for Gram+ve bacteria that are resistant to other antibiotics
Name a drug that interferes with peptidoglycan transport and state its target.
Bacitracin: inhibits bactoprenol regeneration, hence preventing PtG transport
Name a class of drugs that inhibit peptidoglycan incorporation and explain how they do this.
Beta lactams: bind covalently to transpeptidase, inhibiting PtG incorporation into the cell wall
What are the three subsets of beta lactams?
Carbapenems
Cephalosporins
Penicillins