Agents Affecting Nucleic Acids Plasma Membrane Disrupters

Question 1

Flouroquinolones

Answer 1

Ciprofloxacin

Question 2

Antifolattes

Answer 2

Sulfamethoxazole
Trimethoprim

Question 3

Nitroimidazoles

Answer 3

Metronidazole

Question 4

Cyclic lipopeptides

Answer 4

Daptomycin

Question 5

Polymyxins

Answer 5

Colistin

Question 6

Ciprofloxacin mechanism

Answer 6

Bind to DNA-topoisomerase erase complex to inhibit DNA gyrase (G-) and topoisomerase IV (G+)
Bactericidal
Peak/MIC

Question 7

Flouriquinolones spectrum

Answer 7

G- bacilli
G-cocci
Anaerobes
Mycobacteria
Atypical bacteria

Question 8

Fluoriquinolone resistance

Answer 8

Altered gyrase affinity and increase efflux
Qnr proteins protect DNA gyrase

Question 9

Absorption of oral Fluoriquinolone is reduced by _

Answer 9

Divalent cations

Question 10

Fluoriquinolone adverse effects

Answer 10

Black box warning for tendinitis/tendon rupture, CNS effects, peripheral neuropathy
Prolonged QT interval and hypoglycemia
Photosensitivity
Neuromuscular blockade NOT to be used in patients with myasthenia gravis

Question 11

Metronidazole mechanism

Answer 11

Bactriocidal prodrug
Activated by ferredoxin reductase cycle
Produces free radicles that cause lethal DNA strand breaks and loss of helical structure
peak/MIC dependent

Question 12

Metronidazole spectrum

Answer 12

Anaerobes
Anaerobic Protozoa

Question 13

Metronidazole adverse reactions

Answer 13

Headache
GI
Dark red-brown urine
Black box warning: carcinogenic
CNS- peripheral neuropathy
drug interaction when used with alcoholic beverages

Question 14

Antifolates target folate because

Answer 14

Bacteria must synthesize it de nose from pteridine, PABA, and glutamate

Question 15

Sulfamethoxazole mechanism

Answer 15

Bacteriostatic
Structural analog of PABA
Competitive inhibitor of dihydropteroate synthase (mammals do not express this enzyme)

Question 16

Sulfamethoxazole resistance

Answer 16

Increased production of PABA
Mutation in dihydropteroate synthase active site amino acids

Question 17

Sulfamethoxazole adverse reactions

Answer 17

Knicterous in neonates
Hypersensitivity (Stevens-Johnson syndrome)
Hemolytic anemia in patients with G6PD deficiency

Question 18

Trimethoprim mechanism

Answer 18

Competitive inhibitor of DHFR
Blocks dihydrofolate (bacterial DHFR is 40,000 x more sensitive than mammalian)

Question 19

Trimethoprim resistance

Answer 19

increased DHFR synthesis
mutated DHFR with reduced binding affinity

Question 20

Adverse reactions to trimethoprim

Answer 20

Bone marrow suppression in folate-deficient patients
Hyperkalemia (potassium retention leading to cardia arrhythmias

Question 21

Co-trimoxazole

Answer 21

Trimethoprim
Sulfamethoxazole
Bactericidal combinations that inhibits sequential steps of folate biosynthesis
Active against G+ and G-, MRSA opportunistic fungal pathogens

Question 22

Antibiotics affecting nucleic acids

Answer 22

Flouroquinolones
Antifolates
Nitroimidazoles

Question 23

Plasma membrane disrupters

Answer 23

Cyclic lipopeptides
Polymyxins

Question 24

Daptomycin mechanism

Answer 24

Insertion of lipophilic train into plasma membranes to form efflux channels for K+ causing depolarization
Bactericidal
AUC/MIC

Question 25

Daptomycin is only active against

Answer 25

G+

Question 26

Daptomycin is administered

Answer 26

IV

Question 27

Daptomycin adverse reactions

Answer 27

Myopathy (must monitor CK)
Eosinophilia pneumonia

Question 28

Colistin mechanism

Answer 28

Binds - charged LPS and phospholipids on G- bacilli
Hydrophobic tail disrupts inner and outer membranes to increase permeability

Question 29

Colistin activity

Answer 29

Peak/MIC

Question 30

Colistin adverse reactions

Answer 30

Nephrotoxicity
Neurotoxicity