Sulfonamide Antimicrobial Agents Flashcards

1
Q

What is inhibited competitively by the sulfonamides?

A

the incorporation of p-aminobenzoic acid (PABA) into the folic acid nucleus

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2
Q

The sulfonamides inhibit?

A

dihydropteroate synthase

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3
Q

Why do sulfonamides have selective toxicity for bacterial cells as opposed to mammalian cells

A

mammalian cells utilize preformed folates in the diet and some bacterial cells are required to make their own folic acid

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4
Q

How can the antibiotic activity of sulfonamides be reversed?

A

by adding large quantities of PABA to the diet

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5
Q

Sulfonamides in general inhibit?

A
gram (+) and gram (-) bacteria
nocardia
Chlamydia trachomatis
some protozoa and fungi
enteric bacteria such as E. coli, Klebsiella, salmonella, shigella and enterobacter
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6
Q

Why are sulfonamides usually used in combination

A

the resistance factors are too widespread for these drugs to be used in a single drug therapy

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7
Q

What is the antifungal activity of trimethoprim-sulfamethoxazole important for?

A

the treatment of AIDS-infected patients that have developed Pneumocystis carinii (jiroveci)

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8
Q

What does trimethoprim inhibit?

A

dihydrofolate reductase

so combination with sulfamethoxazole inhibits sequential steps in the biosynthesis of tetrahydrofolic acid

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9
Q

Most popular sulfonamide

A

sulfisoxazole (broad spectrum antibiotic activity)

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10
Q

Sulfisoxazole and sulfamethoxazole are mainly used to treat

A

simple urinary tract infections

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11
Q

used as a cream to treat vaginal infections by Gardnerella vaginalis

A

1:1:1 combination of sulfabenzamide, sulfacetamide, and sulfathiazole (triple sulfas)

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12
Q

Triple sulfas-phenylpropanolamine-pheniramine is also used to treat

A

used orally in tablet/suspension to treat sinus and throat infections

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13
Q

What is sulfasalizine used to treat

A

ulcerative colitis and Crohn’s disease

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14
Q

Direct administration of salicylates, including 5-aminosalicyclic acid is?

A

irritating to the gastric mucosa

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15
Q

What is sulfadoxine?

A

long-acting sulfonamide used with pyrimethamine to prevent and treat malaria

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16
Q

What is pyrimethamine

A

inhibitor of Plasmodium falciparum dihydrofolate reductase

17
Q

first-line chemotherapy to treat acute toxoplasmosis

A

sulfadiazine in combination with pyrimethamine

18
Q

All sulfonamides and their derivatives are?

A

cross-allergenic

19
Q

sulfonamide derivates in use include

A

carbonic anhydrase inhibitors, thiazides, furosemide, sulfonylurea hypoglycemic agents etc

20
Q

Most common adverse reactions of sulfonamides

A

allergic reactions - present as rash, photosensitivity, and drug fever

21
Q

potentially fatal adverse reaction of sulfonamides

A

Stevens-Johnson syndrome: rare skin and mucous membrane rash tha tis potentially fata

22
Q

Other adverse reactions of sulfonamides

A

crystalluria and hematopoietic disturbances: asplasmic anemia, granulocytopenia, and thrombocytopenia
anorexia, nausea, and vomiting occurs in 1-2%

23
Q

Resistance to sulfonamides occurs through the following mechanisms

A
  1. mutations that cause overproduction of PABA
  2. mutations in dihydropteroate synthase that decreases its affinity for the sulfonamides
  3. mutations that result in a decrease in cell permeability to the sulfonamides
24
Q

Why do you always give sulfonamides in combination

A

resistance is very common
resistance to combination therapy targeting two enzymes in highly reduced since the microorganism wold have to carry mutations in two enzymes

25
What happens when the dihydrofolate reductase (DHFR) gene is mutated
enables the expressed enzyme to be active in the presence of drug through a decreased binding affinity of trimethoprim