9. antimicrobial drugs II

Question 1

the successful chemotherapeutic agent has _____ toxicity. therefore, it kills or inhibits the pathogen while damaging the host as little as possible

Answer 1

selective toxicity

Question 2

the degree of selective toxicity may be expressed in terms of what two types of doses?

Answer 2

1. therapeutic dose
2. toxic dose

Question 3

this is the drug level at which the agent becomes too toxic for the host

Answer 3

the toxic dose

Question 4

this is the drug level required for treatment of a particular infection

Answer 4

the therapeutic dose

Question 5

this is the ratio of the toxic dose to the therapeutic dose

Answer 5

the therapeutic index

Question 6

the ______ (smaller/larger) the therapeutic index, the better the chemotherapeutic agent in general

Answer 6

larger

Question 7

a drug that disrupts a microbial structure or function not found in host cells often has greater selective toxicity, fewer side effects, and a _____ (low/high) therapeutic index

Answer 7

high

Question 8

what are the three categories that antimicrobial drugs can be classified as?

Answer 8

1. natural
2. semisynthetic
3. chemical synthetic

Question 9

this type of antimicrobial drugs can be natural antibiotics that have been structurally modified by the additional of chemical groups to make them less susceptible to stomach acids and inactivation by pathogens (e.g. ampicillin and amoxicillin)

Answer 9

semisynthetic

Question 10

this type of antimicrobial drugs are produced by bacteria and fungi (e.g. penicillin)

Answer 10

natural

Question 11

this type of antimicrobial drugs includes sulphonamides, trimethoprim, ciprofloxacin, etc.

Answer 11

chemical synthetic

Question 12

this type of antimicrobial agents are effective only against a limited variety of pathogens. e.g. may affect only gram positive and not gram negative bacteria, or may only affect a specific group of gram negative bateria

Answer 12

narrow-spectrum drugs

Question 13

this type of antimicrobial agents attack many different types of bacteria. eg. affect some gram negative and gram positive bacteria

Answer 13

broad-spectrum drugs

Question 14

T/F: chemotherapeutic agents are only bactericidal

Answer 14

false - chemotherapeutic agents can be either cidal or static

Question 15

these agents reversibly inhibit growth. therefore if the agent is removed, the microorganisms will recover and grow again

Answer 15

static agent

Question 16

T/F: the effect of chemotherapeutic agents may vary with the target species. they may be cidal for one species and static for another

Answer 16

true

Question 17

these type of drugs help the immune system get rid of bacteria/infection; if the immune system his weak, elimination of the infection may not occur

Answer 17

static agent

Question 18

the estimate of the effectiveness of an antimicrobial drug against a pathogen can be obtained from the ____________

Answer 18

minimal inhibitory concentration (MIC)

Question 19

the _____ is the lowest concentration of a drug that prevents the growth of a particular pathogen; static drugs

Answer 19

MIC

Question 20

the ______ is the lowest drug concentration that kills the pathogen; cidal drugs

Answer 20

minimal lethal concentration (MLC)

Question 21

what are the three antimicrobial activity tests?

Answer 21

1. dilution susceptibility tests
2. disk diffusion tests
3. the E-test

Question 22

this antimicrobial activity test uses small paper disk, each impregnated with a different antibiotic, and placed on the inoculated agar to test the bacterial susceptibility to drugs

Answer 22

disk diffusion tests

Question 23

this is the most commonly used type of disk diffusion test. the results are interpreted using a table that related zone diameter to the degree of microbial resistance

Answer 23

kirby-bauer method

Question 24

this antimicrobial activity test is often used in sensitivity testing. the MIC can also be determined by this test. the bacterial isolate to be tested for antimicrobial sensitivities is inoculated on the surface of an agar medium and then strips are placed on the surface. each strip contains a gradient of an antibiotic and is labeled with a scale of MIC values. after the incubation time, an elliptical zone of inhibition appears.

Answer 24

E-test

Question 25

where is the MIC determined on the strip of an E-test?

Answer 25

the MIC is determined from the point of intersection between the inhibition zone and the strips scale of MIC values

Question 26

this antimicrobial activity test is used to determine MIC and MLC values. a series of tubes containing broth media with antibiotic in serial concentrations (twofold dilution) are inoculated with the test pathogen.

Answer 26

dilution susceptibility tests/broth dilution test

Question 27

how is the MIC determined from the dilution susceptibility tests/broth dilution test

Answer 27

the lowest concentration of the antibiotic resulting in no growth after incubation is the MIC`

Question 28

how is the MLC determined from the dilution susceptibility tests/broth dilution test

Answer 28

the MLC can be ascertained if the tubes showing no growth are then cultured into fresh medium lacking antibiotic. the lowest antibiotic contraption from which the pathogen do no subsequently grow is the MLC