Antibiotics — Flashcards

Flashcard 551: What is the initial treatment of choice for most patients with early localized Lyme disease? _____

Answer: Oral doxycycline

Flashcard 552: What is the treatment for **prosthetic valve endocarditis** caused by methicillin-susceptible staphylococci? _____

Answer: Nafcillin (or oxacillin, cefazolin) + Rifampin + Gentamicin

Flashcard 553: What drug regimen is most commonly used to treat active tuberculosis? _____

Answer: (1) Rifampin (2) Isoniazid (3) Pyrazinamide (4) Ethambutol (And Vitamin B6)

Flashcard 554: Meningitis is treated empirically with _____ and _____; add ampicillin if Listeria is suspected

Answer: ceftriaxone

Flashcard 555: Tazobactam, sulbactam, and clavulanic acid are _____ that can be added with amoxicillin, ampicillin, or piperacillin to extend their activity to cover gram (+) and (-)

Answer: β-lactamase inhibitors

Flashcard 556: What is the recommended treatment for spontaneous bacterial peritonitis? _____

Answer: Broad-spectrum antibiotics (e.g. cefotaxime)

Flashcard 557: What is the mechanism of action of **Metronidazole**?

Answer: Forms toxic free radical metabolites that cause **DNA strand breakage** and loss of helical structure.

Extra: Metronidazole is a pro-drug that is reduced by the enzyme ferredoxin in anaerobic organisms. The resulting reactive metabolites damage bacterial DNA. Clinical use (mnemonic **GET GAP**): - **G**iardia - **E**ntamoeba - **T**richomonas - **G**ardnerella vaginalis - **A**naerobes (Bacteroides, C. difficile) - **P**ylori (H. pylori)

Flashcard 558: What is the mechanism of action of Nitrofurantoin?

Answer: Bacterial enzymes (flavoproteins) reduce it to reactive intermediates that damage bacterial DNA

Extra: Nitrofurantoin is primarily used for uncomplicated urinary tract infections (cystitis). It is bactericidal and achieves high concentrations in the urine. It is contraindicated in patients with significant renal impairment (CrCl < 60 mL/min) because it won't reach therapeutic concentrations in the urine and may cause systemic toxicity.

Flashcard 559: Anti-_____ drugs, such as dapsone, may induce oxidative stress and are thus contraindicated in patients with G6PD deficiency

Answer: leprotic

Flashcard 560: Mutations in which bacterial enzyme can result in resistance to Rifampin?

Answer: DNA-dependent RNA polymerase