Antibacterial Agents

Question 1

what is the germ theory of disease?

Answer 1

Proposes that microorganisms cause disease

Question 2

what was the first effective treatment for syphilis?

Answer 2

Arsphenamine (Salvarsan)

Question 3

what was the first widely available antimicrobial?

Answer 3

Prontosil

Question 4

what marks the goldern era of antibiotics?

Answer 4

alexander flemming discovering penicillin

Question 5

what is an antibiotic?

Answer 5

chemical substance that has capacity to inhibit growth of or kill bacterial cells

Question 6

what is an antimicrobial?

Answer 6

agents that act against all types of microorganisms not just bacteria

Question 7

what is the difference between a narrow spectrum and broad spectrum antibiotic?

Answer 7

narrow spectrum - effective against limited number
broad spectrum - effective against wider array

Question 8

what is a con of broad spectrum bacteria?

Answer 8

increased development of resistance
disrupts normal microbiome

Question 9

define bactericidal

Answer 9

kills bacteria

Question 10

define bacteriostatic

Answer 10

inhibits growth of bacteria

Question 11

what is selective toxicity?

Answer 11

antibiotic that is more harmful to bacterial cells than to host cells

Question 12

what are the properties of an effective antibiotic?

Answer 12

selective toxicity, soluble in bodily fluids, toxicity not easily altered, nonallergenic, stability, bacterial resistance not easily acquired, reasonable cost

Question 13

what are the 5 classes of antibiotics?

Answer 13

1. inhibition of cell wall synthesis
2. disruption of cell membrane function
3. inhibition of protein synthesis
4. inhibition of nucleic acid synthesis
5. action as antimetabolites

Question 14

what class are the following antibiotics in - B-lactams, vancomycin, and bacitracin?

Answer 14

inhibitors of cell wall synthesis

Question 15

How are bacterial cell walls synthesized?

Answer 15

NAG and NAM get AA added to them > transported across cell membrane > AA side chains cross linked by transpeptidase > membrane formed

Question 16

Are antibiotics that inhibit cell wall synthesis bactericidal or bacteriostatic?

Answer 16

bactericidal

Question 17

How does cell wall inhibitors have selective toxicity?

Answer 17

prokaryotic cells dont have cell walls

Question 18

What type of antibiotics are penicillin and cephalosporins?

Answer 18

B-lactam

Question 19

what is the mode of action of B-lactam antibiotics?

Answer 19

binds to and blocks activity of transpeptidases, preventing cross-linking of peptidoglycan layers

Question 20

what is the mode of action of vancomycin?

Answer 20

blocking transglycosylation and transpeptidation steps of peptidoglycan synthesis

Question 21

which cell wall inhibitor antibiotic is a glycopeptide antibiotic?

Answer 21

vancomycin

Question 22

what is the mode of action of bacitracin?

Answer 22

prevents dephosphorylation of bactoprenol (lipid carrier), preventing assembly and transport of NAG-NAM

Question 23

how is bacitracin applied? why?

Answer 23

topical use only due to toxicity

Question 24

what antibiotic disrupts the cell membrane?

Answer 24

polymyxins

Question 25

what is the mode of action of polymyxin?

Answer 25

cationic detergent, disrupting membrane structure

Question 26

how is polymyxin administered? why?

Answer 26

topical or ophthalmic use only - poor selectivity toxicity

Question 27

what are the two ribosomal subsunits in bacterial protein synthesis?

Answer 27

30s and 50s

Question 28

what is the mode of action of Aminoglycosides?

Answer 28

irreversibly bind to 30s subunit and block initiation complex, causing misreading and premature release of mRNA from ribosome - halts protein synthesis

Question 29

what antibiotic is ototoxic and nephrotoxic to cats and dogs?

Answer 29

aminoglycosides

Question 30

what is the mode of action of tetracycline?

Answer 30

bind to 30s subunit to prevent attachment of aminoacyl-tRNA to RNA-ribosome complex

Question 31

which antibiotic is toxic to the human mitochondria?

Answer 31

amphenicol

Question 32

what is the mode of action of amphenicol?

Answer 32

bind to 50s subunit, inhibiting peptidyl transferase

Question 33

what is the mode of action of macrolides?

Answer 33

bind to 50s subunit, blocking formation of initiation complex and translocation

Question 34

what is the mode of action of lincosamides?

Answer 34

binds to 50s subunit

Question 35

what is the mode of action of streptogramins?

Answer 35

bind to different sites on the 50s ribosomal subunit, inhibition of protein synthesis at different steps

Question 36

which ribosome inhibitor is toxic to rodents?

Answer 36

lincosamides

Question 37

what is the mode of action of Quinolones/Fluoroquinolones?

Answer 37

inhibit DNA gyrase (topoisomerase II) and topoisomerase IV, preventing bacteria DNA from unwinding and duplicating

Question 38

what is the mode of action of rifamycins?

Answer 38

inhibits DNA-dependent RNA polymerase > prevents transcription of messenger RNA

Question 39

what is the mode of action of metronidazole?

Answer 39

pro-drug
reduction of nitro group of metronidazole creates active drug that covalently binds DNA, causing DNA breaks > pieces of DNA get destroyed

Question 40

what is the mode of action of sulfonamides and diaminopyrimidines?

Answer 40

interferes with folic acid synthesis (needed for DNA synthesis)

Question 41

what are the pros and cons of antibiotic use?

Answer 41

pros - gain 4%-5% more body weight, livestock live longer, containment of potentially large-scale epidemics

cons - multidrug-resistant pathogens