Antibiotics Flashcards
What are bacteriostatic drugs?
Slows growth - bacteria cant reproduce
Will start to grow again when drug is removed
Rely on working immune system to clear the rest of
What are bactericidal drugs?
Kills bacteria
What are the two different types of bacteriocidal drugs?
Time dependent drugs
Concentration dependent drugs
What is does a time dependent drug mean?
Drug needs to stay at effective concentrations within the body for as long as possible
Peak conc doesnt matter
What does concentration dependent drug mean?
Peak conc determines effectiveness of drug
Big dose better - quicker
What are inhibitors of peptidoglycan cell wall synthesis?
Beta lactams - penicillins and cephalosporins
What are beta lactams more effective against?
Gram positive bacteria
What can cause beta lactam resistance?
Beta lactamase produced by bacteria to break down the drug
What can be used to inhibit beta lactamases so reduce beta lactam resistance?
Clavulanic acid - given alongside beta lactams
Which is the best beta lactam drug?
Amoxicillin
How are penicillins distributed?
Widely - dont cross blood brain barrier
How are beta lactams eliminated?
By the kidney
What is the therapeutic ratio of beta lactams?
Wide - mammalian cells dont have a cell wall
What adverse reactions are a risk from beta lactams?
Hypersensitivity reactions
GI superinfection - death of gut flora
What antibiotics inhibit bacterial protein synthesis?
Aminoglycosides
Macrolides
Tetracyclines
Chloramphenicol
What effect do aminoglycosides have on bacterial protein synthesis?
Cause misreading of translation - wrong tRNA binds
What type of bacteria do aminoglycosides affect?
Mostly gram negative
More effective against aerobic bacteria - energy dependent to cross outer membrane
Are aminoglycosides bacteriostatic or bacteriocidal?
Bacteriocidal - concentration dependent
Are beta lactams bacteriostatic or bacteriocidal?
Bacteriocidal - time dependent
What are the adverse reactions of aminoglycosides?
Nephrotoxicity - bind to proximal tubule cells
Ear damage
How are aminoglycosides administered?
IV, SC injections
How do macrolides prevent bacteril protein synthesis?
They bind to the P side in the ribosome to prevent translocation of the mRNA
What is an example of a macrolide antibiotic?
Erythromycin
What type of bacteria do macrolides affect?
Gram positive bacteria (not at all gram negative)
Are macrolides bacteriostatic or bacteriocidal?
Bacteriostatic
Erythromycin bacteriocidal at high doses
How do tetracyclines affect bacterial protein synthesis?
Bind to the A site on the ribosome - prevents tRNA binding
What bacteria does tetracyclines affect?
Wide spectrum - everything
But due to this they are prone to resistance
What impairs tetracycline absorption?
Calcium/milk products
What is tetracycline distribution?
Wide - including CNS
Why do tetracyclines not affect mammalian cells?
Dont have the carrier protein to cross cell membrane
What is the main resistance mechanism of bacteria against tetracyclines?
Efflux pump
What adverse reactions can you get to tetracyclines?
GI disturbances
Dont give orally to ruminants
Chelate calcium - affects enamel on teeth
How do chloramphenicols prevent bacterial protein synthesis?
Inhibit peptide bond formation
Are chloramphenicols bacteriostatic or bacteriocidal?
Bacteriostatic
What adverse reactions can chloramphenicols cause?
Anaemia by suppression of bone marrow
How are chloramphenicols administered?
Orally
What type of bacteria do chloramphenicols affect?
Best against obligate anaerobes but also affects all other types
What do antibiotic drugs affecting bacterial DNA synthesis target?
Folate synthesis
What antibiotics affect folate synthesis?
Sulphonamides
Trimethoprim
How do sulphonamides affect bacterial DNA synthesis?
Competitive inhibitor of DHPS enzyme which is used to produce folate
What bacteria types do sulphonamides affect?
Wide spectrum - both gram positive and negative
Are sulphonamides bacteriostatic or bacteriosidal?
Bacteriostatic
What adverse reactions can sulphonamides cause?
Hypersensitivity reactions
How does trimethoprim affect bacterial DNA synthesis?
Inhibits DHFR enzyme
What can trimethoprim be combined with and why?
Sulphonamides
Combination is bacteriocidal
Also effecting against protozoal infections
What is a problem with trimethoprim and sulphonamides combination?
Resistance is a big problem
How do fluoroquinolones affect bacteria?
They interfere with the packaging of the chromosome within the bacteria - interfere with DNA gyrase
What bacteria do fluoroquinolones affect?
Wide spectrum - except obligate anaerobes
Are fluoroquinolones bacteriostatic or bactericidal?
Bactericidal
What adverse reactions do fluoroquinolones cause?
Rare - very popular due to this so shouldnt use as first line treatment (resistance)
How does metronidazole affect bacteria?
Causes DNA fragmentaton
What bacteria does metronidazole affect?
Obligate anaerobes only
How is metronidazole excreted?
Renal and hepatic excretion
What adverse reactions does metronidazole cause?
Rare, usually mild
Cats may salivate a lot
