Antimicrobial Chemotherapy Flashcards
What is chemotherapy?
The use of chemicals to inhibit the growth/replication of ‘invading organisms’ or cancerous cells within the body
What was used to treat bacterial infections before 1946?
Pelargonium roots
Cod liver oil
Gold
What’s the development of antibiotics based on today?
Theory of activity
Result of chance occurrences
What’s the discovery of antibiotics based on today?
Systemic screening of natural products
What’s selective toxicity?
Drugs intended to be toxic to invading organisms / cancerous cells but relatively harmless to host / normal cells
Toxicity of penicillin:
Very low toxicity so high doses can be used
Toxicity of aminoglycosides:
Narrow therapeutic index - toxic dose very close to therapeutic dose
Toxicity of anti-tuberculosis drugs:
Patients may develop hepatotoxicity - not dose related and may require treatment to be stopped
What are peptidoglycan?
Make up bacteria cell wall + don’t occur in eukaryotes
What are peptidoglycan strands made up of?
Amino sugars
N-acetylglucosamine
N-acetylmuramic acid dimers
What gives a bacterial cell wall its strength?
N-actylmuramic acid in peptidoglycan has a short peptide side chain which can be cross-linked with other peptide side chains
Forms latticework in cell wall
Give examples of penicillins:
Penicillins G + V
Beta-Lactamase-resistant penicillins
Broad-spectrum penicillins
Extended-spectrum penicillins
What are Cephalosporins
Come from fungus
Work by same mechanisms as penicillins
What are bacterial folate antagonists?
Antibiotics which inhibit the folate pathway in bacteria
Bacteria become susceptible to drugs which interfere with folate metabolism
What is the folate system important for in bacteria?
Cell metabolism
What marks the beginning of antimicrobial chemotherapy?
Sulphonamides
What are aminoglycosides?
Form ionic bonds at cell surface + penetrate cell wall by transport mechanism across membrane
Diffuse into cytoplasm + bind to bacterial ribosomes
How do aminoglycosides inhibit protein synthesis?
Bind at interface between 30s and 50s subunits in ribosomes
MRNA is misread
What are tetracyclines?
Prevent attachment of tRNA to acceptor site on mRNA-ribosomal complex
Prevents addition of amino acids to peptide chain
What are fluoroquinolones?
Synthetic antibodies
Inhibit DNA gyrase - stops DNA coiling needed for transcription and replication
What are fluroquinolones defined by?
Spectrum of activity and pharmacokinetics
What are fluoroquinolones often limited by?
Impact on other flora
