chapter 20: antimicrobial drugs

Question 1

chemotherapy

Answer 1

the use of drugs to treat a disease

Question 2

antimicrobial drugs

Answer 2

interfere with the growth of microbes within a host

Question 3

antibiotic

Answer 3

a substance produced by a microbe that, in small amounts, inhibits another microbe

Question 4

selective toxicity

Answer 4

the principle that a drug should be toxic to the intended target but not the host (ie a useful antibiotic should kill harmful microbes without damaging the host)

Question 5

bactericidal

Answer 5

kill microbes directly- in many cases most desirable choice (however, may be contraindications…host range, solubility, toxicity, etc.)

Question 6

bacteriostatic

Answer 6

prevent microbes from growing-relies on host’s immune response to finish the job and eliminate the microbes

Question 7

the action of antimicrobial drugs: different ways

Answer 7

1) inhibition of cell wall synthesis: penicillins, cephalosporins, bacitracin, vancomycin
2) inhibition of protein synthesis
3) inhibition of nucleic acid replication and transcription
4) injury to plasma membran
5) inhibition of synthesis of essential metabolites

Question 8

inhibitors of cell wall synthesis

Answer 8

penicillin G, ampicillin, cephalosporins, vancomycin

Question 9

inhibitors of protein syntheis

Answer 9

chloramphenicol, streptomycin, gentamicin, erythromycin

Question 10

inhibitors of nucleic acid synthesis

Answer 10

rifampin

Question 11

competitive inhibitors of the synthesis of essential metabolites

Answer 11

trimethoprim-sulfamethohoxazole

Question 12

action of penicillin on cell wall formation

Answer 12

penicillin block the peptide crosslinking step in peptidoglycan synthesis, thus preventing cross-bridge formation in growing ells, weakens cell wall; cells burst, only active on growing cells **

Question 13

common structure among penicillins?

Answer 13

beta-lactam ring

Question 14

beta-lactam antibiotics

Answer 14

penicillin (penicillinase-resistant penicillins, penicillins + B-lactamase inhibitors), carbapenems (substitue a C for an S, add a double bond), monobactam (single ring)

Question 15

cephalosporins

Answer 15

first gen: narrow spectrum; act against gram-positive bacteria, second gen: extended spectrum includes gram-negative bacterian, third gen: includes pseudomonads; injected, fourth gen: oral

Question 16

penicillinase

Answer 16

an enzyme encoded by some bacteria, often on plasmids, breaks the beta-lactam ring, rendering penicillin inactive and thus, conferring resistance to penicillin on the bacterium

Question 17

augmentin

Answer 17

formulation of [amoxicillin + potassium clavulanate] clavulanate inhibits penicillinase (B-lactamase) thus allowing penicillin (amoxicillin) to remain intact and to work

Question 18

vancomycin

Answer 18

glycopeptide, important “last line” against antibiotic-resistant S. aureus

Question 19

chloramphenicol

Answer 19

binds to 50S potion and inhibits the formation of peptide bond, broad spectrum

Question 20

rifamycin

Answer 20

inhibits RNA synthesis, antituberculosis

Question 21

antibiotic resistance (4 methods)

Answer 21

1) blocking entry
2) inactivating enzymes
3) alteration of target molecule
4) efflux of antibiotic

Question 22

what leads to antibiotic resistance

Answer 22

a variety of mutations

Question 23

mechanisms of antibiotic resistance

Answer 23

1) enzymatic destruction of drug
2) prevention of penetration of drug
3) alteration od drug’s target site
4) rapid ejection of the drug

Question 24

resistance genes are often on ____ or ____ that can be …..

Answer 24

plasmids, transposons, transferred between bacteria

Question 25

_____ of antibiotics selects for resistance mutants

Answer 25

misuse

Question 26

misuse of antibiotics

Answer 26

using outdated or weakened antibiotics, using antibiotics for the common cold and other inappropriate conditions,using antibiotics in animal feed, failing complete the prescribed regimen, using someone else’s leftover prescription

Question 27

synergism

Answer 27

occurs when the effect of 2 drugs together is greater than the effect of either alone

Question 28

antagonism

Answer 28

occurs when the effect of 2 drugs together is less than the effect of either alone