Antimicrobial Mechanism And Spectrum

Question 1

MoA of B-lactams

Answer 1

Cell wall synthesis inhibitors
Bind to penicillin binding proteins
Create pores in walls, cell takes on water, dies

Question 2

Two main subdivisions of b-lactams

Answer 2

Penicillins
Cephalosporins

Question 3

There are ___ major subdivisions of penicillins; however, ______penicillins and ______penicillins are the most common.

Answer 3

4; benzylpenicillins; aminopenicillins

Question 4

There are 4 generations of cephalosporins. What generations are MOST commonly used in veterinary medicine?

Answer 4

1st and 3rd (some 2nd)

Question 5

Penicillin G is an example of a _________

Answer 5

Benzylpenicillin

Question 6

Why are penicillins iffy with staphs?

Answer 6

Staphs produce b-lactamases

Question 7

SoA of Penicillin G

Answer 7

Streps, Anaerobes

Question 8

Name two aminopenicillins

Answer 8

Ampicillin
Amoxicillin

Question 9

SoA of aminopenicillins

Answer 9

Strep, Anaerobes (higher end of dose range may be needed)

Question 10

When may aminopenicillins be useful against gram (-) aerobes?

Answer 10

Drugs concentrate in urine, so reach higher concentrations and are able to treat more gram (-) aerobes in the urine

Question 11

What can be used to extend the spectrum of penicillins to include non MRSA staphylococci and bacteriodes?

Answer 11

B-lactamase inhibitors (Clavulanic acid, Sulbactam)

Question 12

When talking about cephalosporins, the classical definition is that as generation # increases gram (-) coverage __________

Answer 12

Increases (Ex. 3rd generation has more gram (-) coverage than 1st gen)

Question 13

CefAzolin and CephAlexin are ______ generation cephalosporins. What is their spectrum?

Answer 13

1st
Streps, non-MRSA Staphs maybe
Cefazolin can potentially cover some gram (+) anaerobes (not clostridium)
Gram (-) aerobes - Cefazolin +/-, Cephalexin NO

Question 14

What generation is Cefoxitin? When is it most commonly used?

Answer 14

2nd
Surgical prophylaxis for severe dental/gingival disease

Question 15

SoA of 3rd gen cephalosporins

Answer 15

Streps, non-MRSA Staphs, Gram (-) aerobes - may require higher doses (ceftiofur)

Anaerobes - not great for Clostridium, but Cefpodoxime and Cefovecin can get gram (-) anaerobes

Question 16

T/F: 3rd generation cephalosporins are the treatment of choice for Pseudomonas

Answer 16

False - no effect against Pseudomonas

Question 17

B-lactams have EXCELLENT coverage against _________

Answer 17

Streps

Question 18

What 3rd generation cephalosporins has the best gram (-) spectrum?

Answer 18

Cefpodoxime

Question 19

MoA of aminoglycosides

Answer 19

Inhibit protein synthesis at the 30s ribosomal subunit
Some may also work at 50s (amikacin)

Question 20

What are the two common aminoglycosides used?

Answer 20

Amikacin
Gentamicin

Question 21

SoA of aminoglycosides

Answer 21

Gram (-) aerobes
Staphs (including some MRS)

NO streps
NO anaerobes

Question 22

MoA of fluoroquinolones

Answer 22

DNA gyrase inhibition

Question 23

SoA of fluoroquinolones

Answer 23

Gram (-)
Staphs
Rickettsia
Mycoplasma

Streps (rarely)
NO anaerobes

Question 24

T/F: Ciprofloxacin kills horses

Answer 24

True :(

Question 25

T/F: the spectrum of action of fluoroquinolones is very similar to aminoglycosides; however, aminoglycosides work better in purulent environments.

Answer 25

False - Do have similar spectrum, but fluoroquinolones work better in purulent environments

Question 26

MoA of tetracyclines

Answer 26

Inhibit protein synthesis at 30s ribosomal subunit

Question 27

What 3 tetracyclines do we have?

Answer 27

Oxytetracycline Doxycycline Minocycline

Question 28

SoA of tetracyclines

Answer 28

“Jack of all trades, Master of Rickettsia” Gram (+) and gram (-) aerobes, Anaerobes, Rickettsia

Question 29

Rank the tetracyclines by order of greatest activity to lowest activity

Answer 29

Minocycline > doxycycline > oxytetracycline

Question 30

MoA of potentiated sulfonamides

Answer 30

Folic acid pathway inhibitors

Question 31

SoA of potentiated sulfonamides

Answer 31

“Jack of all trades, master of none” Gram (+) and Gram (-) aerobes, some protozoa Don’t use for anaerobes

Question 32

In vitro tests on potentiated sulfonamides _______ anaerobic activity

Answer 32

Overestimate

Question 33

Like aminoglycosides, potentiated sulfonamides have __________ activity in purulent environments

Answer 33

Decreased

Question 34

MoA of macrolides and lincosamides

Answer 34

Protein synthesis inhibition at the 50s ribosomal subunit

Question 35

Name a few macrolides and lincosamides

Answer 35

Macrolides - erythromycin, clarithromycin, azithromycin Lincosamides - clindamycin

Question 36

In what species should clindamycin never be used?

Answer 36

Horses and rabbits

Question 37

SoA of macrolides and lincosamides

Answer 37

Gram (+) aerobes Anaerobes (Clindamycin, Azithromycin)

Question 38

T/F: Macrolides and lincosamides are good for abscesses and intracellular bacteria

Answer 38

True

Question 39

MoA of phenicols

Answer 39

Protein synthesis inhibition at the 50s ribosomal unit

Question 40

SoA of phenicols

Answer 40

Gram (+) aerobes, some gram (-) aerobes Anaerobes Mycoplasma Rickettsia Good for abscess, good for intracellular bacteria

Question 41

MoA of nitroimidazoles

Answer 41

DNA synthesis inhibition through production of toxic metabolites

Question 42

T/F: Metronidazole will never be FDA approved for dogs to treat Giardia

Answer 42

False - now FDA approved

Question 43

SoA of nitroimidazoles

Answer 43

Anaerobes Protozoa

Question 44

T/F: Lincosamides, macrolides, and chloramphenicol are all good for intracellular bacteria and abscesses.

Answer 44

True!