Antimicrobials I Flashcards
Difference between antibiotics and chemotherapeutic agents
Antibiotics are naturally-occurringChemotherapeutic agents are synthetic
Goal of semi-synthetic drugs1)2)3)
1) Alter kinetics2) Reduce toxicity3) Broaden antimicrobial spectrum
When might it be useful for a drug to have a short half life?
If excreted by the kidneys, for a UTIIncreases the amount of antimicrobial in the urinary tract
Which type of bacterium is Bordatella?
Gram - rod
Bordatella intrinsic resistance
Intrinsically resistant to penicillin
Phases of bacterial growth curve1)2)3)
1) Lag phase2) Exponential phase3) Stationary phase
What qualifies an antimicrobial as bactericidal?
Kills 99.9% of bacteria3-log reduction (log10 scale)
When are bactericidal antimicrobials necessary?
In immunocompromised patients
Tetracycline structure
Four hexagonal carbon rings
Structural difference between penicillin and cephalosporin beta-lactams
Penicillin is a beta-lactam ring attached to a pentagonal structureCephalosporins are beta lactam ring attached to a hexagonal structure
Tetracycline pharmacokinetics
Very short half-lifeExcreted in bile
How are tetracyclines excreted?
In bile
Penicillin examples1)2)3)4)5)6)
1) Penicillin G2) Penicillin V3) Ampicillin4) Methicillin5) Flucloxacillin6) Carbenecillin
Penicillin G oral availability
Low
Penicillin V oral availability
Good
Organisms susceptible to penicillin G
Gram + rods, cocciGram - cocci
Organisms susceptible to penicillin V
Gram +rods, cocciGram - cocci
Toxicity of penicillin G and V
Very low
Organisms susceptible to ampicillin
Gram + rods, cocciGram - rods, cocci
Ampicillin oral availability
Good
Ampicillin toxicity
Very low
Methicillin toxicity
Moderate
Organisms susceptible to methicillin
Gram + cocciTargeted against staphylococci
Methicillin oral efficacy
Poor
Organisms susceptible to flucloxacillin
Gram + cocciTargeted against staphylococci
Flucloxacillin toxicity
Low
Flucloxacillin oral availability
Good
Carbenecillin oral availability
Poor
Organisms susceptible to carbenecillin
Gram - rodsTargeted against pseudomonas
Antimicrobials used particularly against gram + cocci, EG: staphylococcus
Methicillin, flucloxacillin
Antimicrobial particularly used against G- rods, EG: pseudomonas
Carbenicillin
Carbenecillin toxicity
Very low
Antimicrobials targeting cell wall1)2)
1) Beta lactams2) Glycopeptides
Antimicrobials targeting cytoplasmic membrane1)2)
1) Polymixins (antibacterial)2) Polyenes (antifungal)
Antimicrobials targeting ribosomes1)2)
1) Aminoglycosides2) Chloramphenicol
Antimicrobials targeting nucleic acids1)2)
1) Rifamycins2) Quinolone
Antimicrobials targeting folic acid synthesis1)2)
1) Sulphonamides2) Trimethoprim
Bacteria innately resistant to sulphanomides
EnterococciCan’t synthesise folate
Can humans synthesise folate?
No
Examples of bacteria to be treated with ampicillin
SalmonellaHaemophilus influenzae
Which antimicrobial would salmonella and H. influenzae be treated with?
Ampicillin
