Antibacterial Drugs - Chemotherapy Flashcards
Why can doctors not tell the specific bacterial infection from symptoms and signs?
Many bacteria can cause the same symptoms.
The symptoms depend on the site, extent of infection and local reaction
What are the categories of bacteria?
Gram positive
Gram negative
What is antibacterial chemotherapy?
Chemicals or substances produced by microorganisms to kill or prevent the growth of other microorganisms
What are the drugs that prevent the growth of a bacterial colony?
Static drugs (only prevent proliferation of bacteria)
What are the drugs that kill the bacteria in a colony reducing their numbers?
Cidal drugs (will remove bacteria)
What are broad spectrum antibacterial drugs?
Affect a wide range of bacterial species and hence are very effective antibiotics
What are narrow spectrum antibacterial drugs?
Antibiotics which can effect a single bacterium and hence are more easily treated against harmful bacteria.
What is an important characteristic of most antibacterial drugs?
High selective toxicity
What is high selective toxicity?
The ability of a drug to effect its target efficiently without causing side effect or by effecting other body cells.
Exploitable differences between the organism and the host
what are the main differences between bacterial and mammalian cells?
Peptidoglycan cell wall
Plasma membrane without sterols
single circular chromosome
Protein synthesis
Energy metabolism (no mitochondria)
What is a class 1 reactions?
not good targets for chemotherapy as they are very similar to human reactions.
What are class 2 reactions?
Some mechanisms are specific to the bacteria.
Identical pathway but might have different sensitivity to the drug
What is an example of class II drug class?
Folate (vitamin B) essential in DNA replication
What are class 3 reactions?
Best drug target.
Products made up of different composition/ structure specific to the bacteria
Why are class 3 reactions the best chemotherapy targets?
Because these reactions are most different between human and bacterial cells and every cell must make its own specific macromolecules
What is folate metabolism?
Humans must produce folate to make DNA
What are the differences in the folate metabolism between humans and bacteria?
Bacteria:
Produce their own folate
Cannot transport it into their bodies
Have the mechanisms to make their own folate
Humans:
Cannot produce own folate
Transport mechanisms to take up preformed folate
What drug interferes with nucleic acid synthesis?
Sulphonamides by inhibiting production of folate
Why do sulphonamides work as inhibitors of folate production?
Analogue of p-aminobenzoic acid (PABA) essential for folate synthesis.
competitive antagonist
Prevent PABA -> folate and therefore folate -> tetrahydrofolate -> DNA
What drug is most effective in targeting bacterial folate production?
Trimethoprim
effects bacterial cells as there is differential sensitivity between folate to tetrahydrofolate in bacterial and mammalian cells.
Why can you not treat infections characterised with pus with sulphonamides?
Since pus is broken down tissue and therefore high in purines and pyrimidines and hence means that even if the folate metabolism is prevented through antibiotics, the bacteria can still make DNA through absorbing the purines/pyrimidines instead.
What is one of the main targets for bacteria and what drugs effect this?
Peptidoglycan synthesis: highly selective as human cells don’t have this structure.
Penicillin's Beta-lactams Cycloserin Glycoproteins Bacitracin
What leads to resistance of penicillin?
Production of Beta-lactamase
What bacteria can produce beta-lactamase and are therefore resistant to penicillin and what other wways is penicillin resistance occuring?
Staphylococci
Gonorrheae
Hemophilus
Reduction of membrane permeability
Modified penicillin binding sites
