What is a live-attenuated vaccine?

Answer: Attenuated vaccine has microbe with selective deletions of genes involved in pathogenesis. Organisms replicate in the host, greatly increasing antigenic stimulation.

Methemoglobinemia occurs when the ferrous (Fe2+) form of iron in hemoglobin is oxidized to the ferric (Fe3+) form and cannot bind O2. What are the clinical manifestations of methemoglobinemia?

Answer: Dyspnea, headaches, dizziness, altered mental status with cyanosis of extremities, and darkened blood. Treat with methylene blue.

Which antibiotic is a PABA analog with a side effect profile that includes hemolysis and methemoglobinemia?

Answer: Dapsone

Name the three drugs commonly used in the treatment of leprosy:

1. Dapsone

2. Rifampin

3. Clofazimine

What are important side effects of INH?

Answer: Hepatotoxicity (avoid alcohol), peripheral neuropathy (vitamin B6 depletion), sideroblastic anemia (vitamin B6 depletion)

What is the mechanism of action for INH?

Answer: Although not proven, it is thought to inhibit mycolic acid synthesis

What are some common side effects of rifampin?

Answer: Red-orange urine, induces P450 potentially leading to impaired efficacy of other drugs, GI symptoms, headache, fever, rash

Why shouldn't rifampin be used as monotherapy?

Answer: Resistance occurs rapidly when used as monotherapy. It can be used alone briefly for N. meningitidis or H. influenzae prophylaxis.

What are common indications for rifampin?

Answer: Treatment of M. tuberculosis and prophylaxis for N. meningitidis or H. influenzae

What is the mechanism of action of rifampin?

Answer: Inhibits DNA-dependent RNA poly-merase by binding to RNA polymerase and blocking elongation of RNA

What is the mechanism of action of ethambutol and what is its unique side effect?

Answer: Inhibits arabinosyl transferase, an enzyme necessary to make the mycobac-terial cell wall. Also causes decreased visual acuity and color vision

Which drugs are commonly used to treat Mycobacterium tuberculosis infection?

Answer: Ethambutol, rifampin, isoniazid (INH), and pyrazinamide

What is the drug of choice for treating simple recurrent UTIs?

Answer: Trimethoprim-sulfamethoxazole (TMP-SMX). Give ciprofloxacin if patient has sulfa allergy.

What are important side effects of trimethoprim?

Answer: Adverse effects include megaloblastic anemia, leukopenia, and granulocytope-nia. Alleviate these symptoms with supplemental folinic acid.

What is the mechanism of action of trimethoprim?

Answer: Inhibits bacterial dihydrofolate reductase

What are some other side effects of sulfonamides?

Answer: Induce hemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient patients, photosensitivity, and hypersensitivities

What is the main risk of giving sulfonamides during pregnancy?

Answer: Sulfonamides can displace bilirubin from plasma albumin-binding sites and induce kernicterus in the newborn.

Can bacteria obtain folic acid by diffusion or active transport?

Answer: No, bacteria must synthesize folic acid from PABA.

Which enzyme in bacterial folate synthesis is inhibited by sulfonamides?

Answer: Dihydropteroate synthetase

Name two antibiotics that inhibit bacterial growth by acting as p-aminobenzoic acid (PABA) analogs:

1. Sulfonamides

2. Dapsone