antimicrobial therapy

Question 1

what is a chemotherapeutic agent

Answer 1

a chemical agent that is used internally to kill/inhibit the growth of microbes

Question 2

what type of agent is a chemotherapeutic agent

Answer 2

chemical

Question 3

what trait should a chemotherapeutic agent have to be successful

Answer 3

selective toxicity

Question 4

define selective toxicity

Answer 4

ability to kill/inhibit growth of the microbe without damaging the host

Question 5

how can the degree of selective toxicity be expressed (2 things)

Answer 5

therapeutic dose
toxic dose

Question 6

what is the therapeutic index

Answer 6

toxic dose divided by therapeutic dose

Question 7

do we want a low or a high therapeutic index? explain

Answer 7

high; means we have a large toxic dose so we can give the drug at a low concentration

Question 8

in regards to TI, when might side effects occur

Answer 8

when there is a low TI

Question 9

list some side effects from a chemotherapeutic agent

Answer 9

allergic responses, toxicity, renal failure

Question 10

list some targets of prokaryotes (microbes) that can be used when we’re looking for selective toxicity (ie what can we target the drug to that wont be in the host)

Answer 10

capsule, cell wall (peptidoglycan), 70S ribosomes

Question 11

define narrow spectrum

Answer 11

the agent is effective against a small number of pathogens

Question 12

define broad spectrum

Answer 12

the agent is effective against a large number of pathogens

Question 13

what might you call a drug that works against fungi

Answer 13

antifungal

Question 14

what might you call a drug that inhibits the growth of fungi

Answer 14

fungistatic

Question 15

T or F: the chemo agent isn’t useful if it only inhibits the growth of a microbe and not kills it

Answer 15

false; it is still useful bc after growth is inhibited then the immune system can kick in to kill it

Question 16

how are antibiotics made

Answer 16

synthesized by microbes

Question 17

example of an antibiotic

Answer 17

penicillin G

Question 18

how are synthetics made

Answer 18

via chemical procedures

Question 19

what are semisynthetics

Answer 19

agents that are combinations of synthetics and antibiotics (both synthesized by microbes and chemical procedures)

Question 20

example of a semisynthetic

Answer 20

ampicillin

Question 21

what does MIC stand for

Answer 21

minimum inhibitory concentration

Question 22

what is the MIC

Answer 22

lowest conc. of a drug that inhibits the growth of the pathogen

Question 23

what does MLC stand for

Answer 23

minimum lethal concentration

Question 24

what is the MLC

Answer 24

lowest conc. of the drug that kills the pathogen

Question 25

T or F: different species will have different susceptibilities to chemotherapeutic agents

Answer 25

true

Question 26

T or F: susceptibility may change with time

Answer 26

true

Question 27

list three susceptibility tests that may be done

Answer 27

dilution susceptibility disk diffusion (Kirby-Bauer) E test

Question 28

what is the dilution susceptibility test used for

Answer 28

determining the MIC and MLC

Question 29

procedure of the dilution susceptibility test

Answer 29

dilutions of the drug are made in Meuller-Hinton broth or agar, each tube is inoculated with a standard amount of bacteria, after 16-20 hours incubation the presence of growth is noted

Question 30

what type of broth/agar is used in the dilution susceptibility test

Answer 30

Meuller-Hinton

Question 31

procedure of disk diffusion test (Kirby-Bauer)

Answer 31

inoculate on agar plate with a standardized amount of the microbe. A filter disk impregnated with a known conc of the agent is placed on the surface + incubated. The antibiotic will diffuse into the agar. The diameter of the no-growth zone is measured

Question 32

procedure of the E test

Answer 32

uses a plastic coated strip that contains a gradient of antibiotic concentrations + the MIC is read from the scale printed on the strip

Question 33

list the five major modes of action of antibacterial drugs

Answer 33

inhibition of cell wall synthesis, inhibition of protein synthesis, injury to PM, inhibition of nucleic acid synthesis, inhibition of essential metabolites

Question 34

how do agents inhibit cell wall synthesis

Answer 34

prevent NAM subunit crosslinking in peptidoglycan layer

Question 35

do drugs that inhibit cell wall synthesis have a high or low TI

Answer 35

high TI

Question 36

how do agents inhibit protein synthesis

Answer 36

they bind with prokaryotic ribosomes (50S or 30 S subunit) and inhibit translation

Question 37

do agents that inhibit protein synthesis have a high or low TI

Answer 37

high TI

Question 38

how do agents cause injury to the PM

Answer 38

they change the permeability by incorporating themselves into it, thereby damaging its integrity, resulting in cell leakage

Question 39

how do agents inhibit nucleic acid synthesis

Answer 39

they interfere with DNA replication and transcription processes

Question 40

how do agents inhibit essential metabolites

Answer 40

they interfere with metabolic pathways by competitively inhibiting the use of the normal substrate by the enzyme

Question 41

what do sulfa drugs work against

Answer 41

microbes that make their own folate

Question 42

why do sulfa drugs work against microbes that make their own folate

Answer 42

humans get folate from our diet, so the sulfa drugs will only target the pathogen and not the host