Antibiotics Mech of Action and Spectrum

Question 1

Beta Lactam Mechanism of Action

Answer 1

Beta lactam antibiotics work by cell wall synthesis inhibition by binding to penicillin binding proteins. This prevents cross linking of the wall creating pores in the wall that allow swelling of the cell resulting in death

Question 2

Drugs in the Beta Lactam Class

Answer 2

Penicillins
Aminopenicillins
Extended spectrum penicillins
Anti-staphylococcal penicillins
Cephalosporins

Question 3

beta lactamases

Answer 3

enzyme that bacteria releases to inactivate beta lactam antibiotics

Question 4

Benzylpenicillins spectrum

Answer 4

These penicillins such as procaine G are mainly used for streps (+) and anaerobes. It is highly susceptible to Beta lactamases when used for staph and penicillinase for bacteroides fragilis

Question 5

Aminopenicillins spectrum

Answer 5

Aminopenicillins are used for streps (+), anaerobes, and some gram negative aerobes in urine. It is also highly susceptible to beta lactamases and bacteroides fragilis penicillinases

Question 6

sulbactam and clavulanate

Answer 6

beta lactamase inhibitors that are commonly combined with amoxicillin

Question 7

Cefazolin spectrum

Answer 7

This first generation cephalosporin is mainly used for streps and gram + aerobes

Question 8

Cefoxitin spectrum

Answer 8

This 2nd generation cephalosporin is mostly used for surgical prophylaxis in cases of anaerobes (think dentals) and staph

Question 9

Third generation cephalosporins spectrum

Answer 9

These mainly treat streps, some anaerobes and gram negatives at higher doses. Examples are ceftiofur, cefpodoxime proxetil, and cefovecin. Ceftiofur doesn’t cover staphs at all, cefpodoxime provides the best gram negative coverage and cefovecin is convenia (long acting)

Question 10

T/F: all beta lactams are good choices for streps

Answer 10

T

Question 11

what beta lactams are good choices for staphs?

Answer 11

cephalosporins and penicillins plus beta lactamase inhibitors

Question 12

T/F: aminopenicillins are good for all gram negative infections

Answer 12

F, only good for gram negative infections in urine

Question 13

what generation of cephalosporins have the best gram negative coverage?

Answer 13

third generation (think cefpodoxime)

Question 14

what beta lactam has the best anaerobic spectrum?

Answer 14

penicillins and aminopenicillins

Question 15

aminoglycosides mechanism of action

Answer 15

These antibiotics are bacteriocidal and bind the 30s ribosomal subunit which causes faulty proteins to be added to the membrane which increase cell permeability leading to death

Question 16

what species are aminoglycosides most commonly used in?

Answer 16

horses

Question 17

aminoglycoside spectrum of action

Answer 17

gram negative and staphs but remember that they are inactivated by dead cells (think about draining and lavage before administering)

Question 18

Fluoroquinolones mechanism of action

Answer 18

Fluroquinolones are DNA gyrase (what doubles dna) inhibitors that primarily target gram negative bacteria

Question 19

fluoroquinolones spectrum

Answer 19

fluoroquinolones cover mostly gram negative and staphs

Question 20

whats a good factor to consider when choosing between an aminoglycoside and fluoroquinolone?

Answer 20

fluoroquinolones are more active in purulent enviroments and safer for the kidneys but not cartilage

Question 21

Tetracyclines mechanism of action

Answer 21

inhibition of protein synthesis by preventing the attachment of amino-acyl tRNA to the acceptor site on the 30s ribosomal subunit

Question 22

tetracyclines spectrum of action

Answer 22

gram positive and negative aerobes, anaerobes and rickettsia making it a broad spectrum antibiotic

Question 23

potentiated sulfonamides mech of action

Answer 23

inhibit the folic acid pathway that bacteria must make on their own

Question 24

potentiated sulfonamides spectrum

Answer 24

gram positives and negative aerobes and protozoa but has decreased activity in purulent environments

Question 25

macrolide, lincosamide and phenicol mech of action

Answer 25

inhibit protein synthesis at the 50s ribosomal subunit

Question 26

macrolides spectrum

Answer 26

gram positive and negative aerobes, R equi, L intracellularis, anaerobes, varies with drug

Question 27

lincosamides spectrum

Answer 27

clindamycin and lincomycin are used for gram positive aerobes and anaerobes *will kill horses**

Question 28

phenicols spectrum

Answer 28

these are truly broad spectrum and can be used for gram pos and neg aerobes, anaerobes, mycoplasma and rickettsia

Question 29

nitroimidazoles (metronidazole) mech of action and spectrum

Answer 29

These work by production of a toxic metabolite that causes DNA synthesis inhibition. The spectrum of activity is anaerobes and protozoa