Antimicrobial Mechanism And Spectrum Flashcards
MoA of B-lactams
Cell wall synthesis inhibitors
Bind to penicillin binding proteins
Create pores in walls, cell takes on water, dies
Two main subdivisions of b-lactams
Penicillins
Cephalosporins
There are ___ major subdivisions of penicillins; however, ______penicillins and ______penicillins are the most common.
4; benzylpenicillins; aminopenicillins
There are 4 generations of cephalosporins. What generations are MOST commonly used in veterinary medicine?
1st and 3rd (some 2nd)
Penicillin G is an example of a _________
Benzylpenicillin
Why are penicillins iffy with staphs?
Staphs produce b-lactamases
SoA of Penicillin G
Streps, Anaerobes
Name two aminopenicillins
Ampicillin
Amoxicillin
SoA of aminopenicillins
Strep, Anaerobes (higher end of dose range may be needed)
When may aminopenicillins be useful against gram (-) aerobes?
Drugs concentrate in urine, so reach higher concentrations and are able to treat more gram (-) aerobes in the urine
What can be used to extend the spectrum of penicillins to include non MRSA staphylococci and bacteriodes?
B-lactamase inhibitors (Clavulanic acid, Sulbactam)
When talking about cephalosporins, the classical definition is that as generation # increases gram (-) coverage __________
Increases (Ex. 3rd generation has more gram (-) coverage than 1st gen)
CefAzolin and CephAlexin are ______ generation cephalosporins. What is their spectrum?
1st
Streps, non-MRSA Staphs maybe
Cefazolin can potentially cover some gram (+) anaerobes (not clostridium)
Gram (-) aerobes - Cefazolin +/-, Cephalexin NO
What generation is Cefoxitin? When is it most commonly used?
2nd
Surgical prophylaxis for severe dental/gingival disease
SoA of 3rd gen cephalosporins
Streps, non-MRSA Staphs, Gram (-) aerobes - may require higher doses (ceftiofur)
Anaerobes - not great for Clostridium, but Cefpodoxime and Cefovecin can get gram (-) anaerobes
T/F: 3rd generation cephalosporins are the treatment of choice for Pseudomonas
False - no effect against Pseudomonas
B-lactams have EXCELLENT coverage against _________
Streps
What 3rd generation cephalosporins has the best gram (-) spectrum?
Cefpodoxime
MoA of aminoglycosides
Inhibit protein synthesis at the 30s ribosomal subunit
Some may also work at 50s (amikacin)
What are the two common aminoglycosides used?
Amikacin
Gentamicin
SoA of aminoglycosides
Gram (-) aerobes
Staphs (including some MRS)
NO streps
NO anaerobes
MoA of fluoroquinolones
DNA gyrase inhibition
SoA of fluoroquinolones
Gram (-)
Staphs
Rickettsia
Mycoplasma
Streps (rarely)
NO anaerobes
T/F: Ciprofloxacin kills horses
True :(
T/F: the spectrum of action of fluoroquinolones is very similar to aminoglycosides; however, aminoglycosides work better in purulent environments.
False - Do have similar spectrum, but fluoroquinolones work better in purulent environments
MoA of tetracyclines
Inhibit protein synthesis at 30s ribosomal subunit
What 3 tetracyclines do we have?
Oxytetracycline
Doxycycline
Minocycline
SoA of tetracyclines
“Jack of all trades, Master of Rickettsia”
Gram (+) and gram (-) aerobes, Anaerobes, Rickettsia
Rank the tetracyclines by order of greatest activity to lowest activity
Minocycline > doxycycline > oxytetracycline
MoA of potentiated sulfonamides
Folic acid pathway inhibitors
SoA of potentiated sulfonamides
“Jack of all trades, master of none”
Gram (+) and Gram (-) aerobes, some protozoa
Don’t use for anaerobes
In vitro tests on potentiated sulfonamides _______ anaerobic activity
Overestimate
Like aminoglycosides, potentiated sulfonamides have __________ activity in purulent environments
Decreased
MoA of macrolides and lincosamides
Protein synthesis inhibition at the 50s ribosomal subunit
Name a few macrolides and lincosamides
Macrolides - erythromycin, clarithromycin, azithromycin
Lincosamides - clindamycin
In what species should clindamycin never be used?
Horses and rabbits
SoA of macrolides and lincosamides
Gram (+) aerobes
Anaerobes (Clindamycin, Azithromycin)
T/F: Macrolides and lincosamides are good for abscesses and intracellular bacteria
True
MoA of phenicols
Protein synthesis inhibition at the 50s ribosomal unit
SoA of phenicols
Gram (+) aerobes, some gram (-) aerobes
Anaerobes
Mycoplasma
Rickettsia
Good for abscess, good for intracellular bacteria
MoA of nitroimidazoles
DNA synthesis inhibition through production of toxic metabolites
T/F: Metronidazole will never be FDA approved for dogs to treat Giardia
False - now FDA approved
SoA of nitroimidazoles
Anaerobes
Protozoa
T/F: Lincosamides, macrolides, and chloramphenicol are all good for intracellular bacteria and abscesses.
True!
