antimicrobials

Question 1

list several sources of antimicrobials

Answer 1

1. semi-synthetic:based on an existing natural antibiotic(b-lactanms:ampicillin,aminoglycosides)
2. synthetic:relatively rare(sulfa drugs, quinolones, oxazolidinones)
3. natural source:from microbes.eg:actinomycetes, fungi

Question 2

list the major classes of antibiotics with examples

Answer 2

b-lactams.glycopeptides,polypeptides.polymyxins. tetracyclines.aminoglycosides.sulfonamides. isoniazid

Question 3

describe the different mechanisms of action of major antibiotic classes

Answer 3

1. cell wall synthesis:b-lactams,glycopeptides.polypeptides
2. nucleic acid synthesis:DNA:quinolones;RNA:rifamycins
3. cell membrane disruption:polymyxins
4. protein synthesis:bind to 30s&50s
5. metabolic antagonism:sulfonamides(sulfa drugs),isoniazid

Question 4

describe several major mechanisms of drug resistance

Answer 4

1. decreased permeablitiy(reduced influx)
2. inactivating enzymes
3. altered target sites
4. active efflux
5. alternate pathway

Question 5

nucleic acid synthesis antibiotic DNA

Answer 5

quinolones:ciprofloxacin, norfloxacin

Question 6

nucleic acid synthesis antibiotic RNA

Answer 6

rifamycins

Question 7

nucleic acid synthesis antibiotic RNA

Answer 7

rifamycins

Question 8

glycopeptides mechanisms

Answer 8

cell wall synthesis:bind to peptidoglycan,blocking transpeptidase action
eg:vancomycin,teicoplanin

Question 9

polypetides

Answer 9

interferes with bacoprenol, a carrier molecule that moves peptidoglycan precursors across inner cell membrane.
eg.bacitracin

Question 10

Tetracyclines mechanisms

Answer 10

bind to the 30s ribosomal subunit bacteriostatic activity(G+/-)

Question 11

Aminoglycosides mechanisms

Answer 11

bind to 30s ribosomal subunit bactericidal activity(G-

Question 12

streptogramins mechanisms

Answer 12

bind to 50s ribosomal subunit

Question 13

interfere with folic acid synthesis

Answer 13

sulfonamides

Question 14

mycobacterial infections

Answer 14

isoniazid

Question 15

inhibit synthesis of mycolic acid”cord factor”

Answer 15

isoniazid

Question 16

drug resistance

Answer 16

1. decreased permeability(reduce influx)
2. inactivating enzymes
3. altered target sites
4. active efflux
5. alternate pathways

Question 17

alter target sites

Answer 17

target enzyme or organelle is modified
eg. modified cell wall intermediates
     ribosomal point mutation
     altered penicilin binding proteins
     low enzyme affinity for the drug
     mutation in RNA polymerase

Question 18

vancomycin resistance

Answer 18

modified cell wall intermediates

Question 19

macrolide resistance

Answer 19

ribosomal point mutation

Question 20

pencillin resistance

Answer 20

altered penicillin binding proteins

Question 21

sulfonamide resistance

Answer 21

low enzyme affinity for the drug

Question 22

rifampin(mycobacterial) resistance

Answer 22

mutation in RNA polymerase

Question 23

active efflux

Answer 23

drug is physically pumped out of the cell

Question 24

alternative pathways

Answer 24

use alternative pathway bypasses the sequence inhibited by the agent
OR increase production of the target metabolite
OR pathogen uses preformed folic acid from the surroundings
OR increases the rate of production(overproduction of PABA, increased produciton of enzymes)