47: Antibiotics I

Question 1

pairs
chains
grapelike clusters
rods
spiral shaped

Answer 1

diplococci
streptococci
staphylococci
bacilli
spirochetes

Question 2

all bacteria have a cell wall that consists of _____

Answer 2

peptidoglycan

a macromolecule composed of peptides and sugars that provide a rigid support structure that is found only in bacteria

Question 3

thick wall v. thin wall

Answer 3

gram + = thick

gram - = thin

Question 4

makes up the outer membrane structure of gram - bacteria cell wall

Answer 4

lipoplysaccharide LPS

Question 5

effect of LPS on antibiotics (g-)

Answer 5

retards or prevents penetration of bulk, high molecular weight antibiotics, such as erythromycin

Question 6

effect of lipid bilayer of cytoplamic membrane on antibiotics (g-)

Answer 6

penetration of water-soluble drugs is severely hindered

Question 7

effect of hydrophillic pores on antibiotics (g-)

Answer 7

allow penetration of water-soluble mkolecules up to 650 Da such as sulfonamides

Question 8

effect of nutrient receptor prtns on outer membrane on antibiotics (g-)

Answer 8

agents structurally related to nutrients (sideromycins) utilize these natural receptors

Question 9

effect of teichoic and teichuronic acid on antibiotics (g+)

Answer 9

strong anionic character of these polymers may affect rate of penetration

Question 10

effect of lipid bilayer of cytoplasmic membrane on antibiotics (g+)

Answer 10

rate of penetration depends on lipophilicity (water soluble drugs are hindered)

Question 11

effect of nutrient transport prtns of cytoplasmic membrane on antibiotics (g+)

Answer 11

facilitate rapid penetration of agents similar in structure

Question 12

treatment of a disease with the use chemicals to kill or impair the growth of microorgansims or cancerous cells

Answer 12

chemotherapy

Question 13

EC50 v. Emax

Answer 13

inhibitory concentration at which 50% of the organisms are killed or stop growing

maximum effect

Question 14

aimed at killing or impairing growth of the specific target organism without harming the host

Answer 14

selective toxicity

Question 15

bactericidal v. basteriostatic

Answer 15

agent that will kill the bacteria

agent that will inhibit growth of bacteria but will not will bacteria

Question 16

lowest concentration of a n antimicrobial agent that will inhibit the visible growth of bacteria in liquid culture

Answer 16

MIC minimum inhibitory concentration

Question 17

concentration of antibiotic from the original MIC plate that shows NO growth after subculture

Answer 17

MBC minimum bactericidal concentration

Question 18

treatment in the absence of infection in order to prevent disease

Answer 18

prophylactic therapy

Question 19

treatment of high-risk patients that have become infected but are asymptomatic

Answer 19

pre-emptive therapy

Question 20

treatment of a symptomatic patient without further testing or confirmation of the organism

Answer 20

empirical therapy

Question 21

treatment once the pathogenic organism has been identified and appropriate drug identified

Answer 21

definitive therapy

Question 22

generally a low dose therapy used as a secondary prophylaxis. Problem that caused initial infection is likely still present

Answer 22

suppressive therapy

Question 23

resistance develops due to (6) …

Answer 23

1. reduced drug entry in to the organism
2. increased drug export from the organism
3. expression of enzymes by the organism that destroy the drug
4. changes in expression enzymes that activate the drug
5. impaired drug binding to the original target
6. development of new or different pathways that are not inhibited by the drug

Question 24

bacteria will development resistance through (2)

Answer 24

• acquisition of new genetic material

- mutation in the existing genome

Question 25

“ESKAPE” bacteria

Answer 25

enterococcus faecium
staphylococcus aureus
Klebsiella pneumoniae
Acinetobacter baumanni
Pseudomonas aeruginosa
Enterobacter species

Question 26

resistance of daptomycin

Answer 26

increased positive charge due to the addition of L-lysine to phosphatidylglycerol of the membrane –> reduced drug entry in to the organism

Question 27

resistance of tetracycline

Answer 27

efflux pump is expressed on the cytoplasmic membrane and actively pumps drug out of the cell –> increased drug export from the organism

Question 28

resistance of metronidazole

Answer 28

chemical reduction of metronidazole “activates” the drug. Mutation in reducing enzymes will result in impaired drug activation –> changes in expression enzymes that activate the pro-drug

Question 29

resistance of aminoglycosides

Answer 29

phosphorylation, adenylation, and acetylation of streptomycin can alter target (bacterial ribosome) binding –> expression of enzymes by the organism that destroy the drug

Question 30

resistance of amoxicillin

Answer 30

expression of the enzyme b-lactamase which can hydrolyze the lactam ring of amoxicillin (as well as other penicillins and cephalosporins) and render the compound ineffective –> expression of enzymes by the organism that destroy the drug

Question 31

resistance of trimethoprim & sulfonamides

Answer 31

expression of the drug-insensitive enzymes dihydropteroate synthase and dihydrofolate reductase –> impaired drug binding to the original target

Question 32

resistance of vancomycin

Answer 32

substitution on the peptidoglycan stem so that agent can no longer bind to target –> development of new or different pathways that are not inhibited by drug