Ch 20 Antimicrobial Drugs

Question 1

define chemotherapy

Answer 1

use of drugs to treat a disease (ex: antibiotics)

Question 2

define antibiotics

Answer 2

subs. produced by a mircobe that, in small amounts, inhibits another microbe

Question 3

where antibiotics come from

Answer 3

chemicals evolved by microbes in an attempt to inhibit others around them

Question 4

define selective toxicity

Answer 4

killing microbes w/o damaging host (criteria of human antibiotics)

Question 5

difference between broad spectrum and narrow spectrum antibiotics

Answer 5

broad spectrum- Ab’s that affect a wide range of bacteria (gram-pos and neg)
narrow- Ab’s w specific range and only effect small # of bacteria types

Question 6

what is a superinfection

Answer 6

infection that occurs as a result of overgrowth of microbes after a broad spectrum Ab reduces the number of normal microbiota (destroys a microbes competitor)

Also applies to growth of pathogen that has developed resistance

Question 7

antibiotics work on fast or slow growing bacteria

Answer 7

fast (ex: clostridium difficile is slow growing, survives while others die, can overgrow)

Question 8

5 major action modes of Antimicrobial drugs

Answer 8

Inhibition of cell wall synth., protein synth., nucleic acid replication and transcription ;
injury to PM, inhibition of essential metabolite synthesis

Question 9

how antimicrobials inhibit cell wall synthesis

Answer 9

inhibits formation of peptide cross bridges-> cell “falls apart”

Question 10

how chloramphenicol inhibits protein synthesis

Answer 10

binds to 50S portion of ribosome, inibits formation of peptide bond-> no polypeptide strands made and no proteins made

Question 11

how tetracyclines work to inhibit protein synthesis

Answer 11

interfere w attachment of tRNA to mRNA (no protein synthesized)

Question 12

how streptomycin works to inhibit protein synthesis

Answer 12

changes the shape of 30S ribosome portion-> incorrect reading of mRNA-> non-functioning proteins produced

Question 13

why inhibition of nucleic acid synthesis is problematic

Answer 13

can inhibit host DNA replication as well as bacterial

Question 14

why inhibition of protein synthesis can be problematic

Answer 14

bacterial and mitochondrial ribosomes same size, side effects bc low functioning mitochondria

Question 15

how certain antibiotics work to injure the PM

Answer 15

some block fatty acid synthesis (prevent formation of bilayer)

Question 16

which antibiotic major action mode is most effective against gram neg bacteria

Answer 16

injury to PM

Question 17

example of an antibiotic that works by inhibiting an essential metabolite

Answer 17

solfanilamide- acts as competitive inhibitor of metabolic pathway that uses PABA to make folic acid (critical for nucleic acid synthesis)

Question 18

what is MIC

Answer 18

minimal inhibitory concentration; lowest antibiotic concentration that prevents visible bacterial growth

Question 19

tests to determine MIC

Answer 19

gradient diffusion method “E test” (gradient strip of antibiotic agent) or disk diffusion method (of each paper disk same antibiotic at diff concentrations)
Or a microdillution/ microtiter- growth of microbes w/in Wells with decreasing concentration of drug

Question 20

while a variety of mutations can lead to antibiotic resistance abilities, what other method of developing these abilities is more likley

Answer 20

resistant genes already on plasmids or transposons are present in a population of bacteria, transferred

Question 21

examples of missuse of antibiotics

Answer 21

taking antibiotics that are outdated or weakened, not yours, for inappropriate conditions like the common cold, or antibioitcs in animal feed or not completing antibiotic regimen

Question 22

how bacteria become antibiotic resistent by blocking entry of antibiotic

Answer 22

change cell wall, doesnt allow in

Question 23

how bacteria use enzymes to become antibiotic resistent

Answer 23

develope, evolve, or select for enzymes that can inactivate antibiotics

Question 24

how bacteria utilize target molecules to become antibiotic resistant

Answer 24

many antibodies work by targeting a specific mlcl, bacteria may alter it so they wont be effective

Question 25

bacteria can evolve efflux pumps, which do what to increase antibiotic resistence

Answer 25

pump out antibodies faster than they can effectively work