Session 4 - Antimicrobials Flashcards
What are the ideal features of antimicrobial agents
- selective toxicity
- few adverse effects
- reach site of infection
- can be given orally or through IV
- long half life
- doesn’t interfere with other drugs
What are the 4 mechanisms of action of antimicrobials
- inhibiting cell wall synthesis
- inhibiting protein synthesis
- inhibiting cell membrane function
- nucleic acid synthesis
What 2 classes of antimicrobials inhibit cell wall synthesis
Beta-lactams
Glycopeptides
What class of antimicrobials inhibit cell membrane function
Polymixins
What class of antibacterials prevent protein synthesis
- tetracyclines
- aminoglycosides
- macrolides
What class of antibacterials prevent nucleic acid synthesis
Quinolones
How does penicillin prevent cell wall synthesis
Binds to the penicillin binding proteins which forms the cross in bridges between the side groups of the peptidoglycan preventing the cross bridges forming
How does vancomycin prevent the synthesis of bacteria cell wall
Prevents cross linkages but binding to the cell wall preventing the penicillin binding protein from binding
Under which antibacterial class is vancomycin in
Glycopeptides
Under which antibacterial class does penicillin fall under
Beta-lactams
What are bacteria cell walls made up of
Peptidoglycan (chains of amino acids and peptides)
What are the 3 types of resistance
- intrinsic
- acquired
- adaptive
What is intrinsic resistance
Where there is target for the drug so it cant enter the bacteria
This is usually permanent
What is acquired resistance
Where the organism acquires new genetic material or mutates
Usually permanent
What is adaptive resistance
Where the organism responds to the stress of antimicrobials and so high levels of antimicrobials allow the microbe to become resistant
This is reversible as you can take away the stress
What are the 3 mechanisms of resistance
- drug inactivating enzymes
- altered target
- altered uptake
What are the 2 genetic mechanisms for antibiotic resistance
- gene mutation
- gene transfer
What is transduction gene transfer
Where bacteriophage viruses insert the gene into the bacteria
What is transformation gene transfer
Where free DNA can enter at porins in the bacteria cell wall
How can you measure antibiotic activity
By disc testing to see what much the organism grows
what are the 4 classifications of antimicrobial agents
- chemical structure
- target site
- spectrum
- bactericidal or bacteriostatic
what are bactericidal agents
antimicrobials that kill bacteria
what are bacteriostatic agents
antimicrobials which inhibit bacteria growth
how do antimicrobials prevent nucleic acid synthesis
by inhibiting the actions of 2 nuclear enzymes inhibiting DNA replication
how does altering the target for antimicrobials cause resistance
it means the target enzyme for the antimicrobial has a lower affinity for it
give 2 examples of drug inactivating enzymes which cause antimicrobial resistance
B-lactamases
aminoglycoside enzymes
what uptake can be altered to cause antimicrobial resistance
- a decreased permeability
- increased efflux
how do antimicrobials usually enter through the cell wall
through holes called porins