DNA inhibiting antibiotics

Question 1

fluorquinolones (4)

Answer 1

suffix “floxacin”– ciprofloxacin, levofloxacin, gemifloxacin, moxifloxacin

Question 2

fluoroquinolone mechanism

Answer 2

Target DNA gyrase and topoisomerase IV. Inhibition of unwinding of DNA is rapidly bactericidal

Question 3

resistance to fluoroquinolones

Answer 3

plasmid mediated. Qnr proteins that protect DNA gyrase, or aminoglycoside acetyltransferase that modifies ciproflaxin

Question 4

nitrofurantoin

Answer 4

“urinary tract antiseptic.” Cannot be used for systemic infection b/c dose necessary to achieve therapeutic plasma concentration is toxic. Instead, given orally, concentrates in renal tubules, treats UTIs.

Question 5

nitrofurantoin mechanism

Answer 5

Reduced by bacterial enzymes to intermediates that damage bacterial DNA, producing a concentration dependent bacteriostatic or bactericidal effect. Selectively toxic because mammalian enzymes don’t reduce nitrofurantoin as rapidly.

Question 6

nitro pharmacokinetics

Answer 6

rapid, complete GI abs. Rate is linearly related to renal function (creatinine clearance), so renal impairment can decrease drug efficacy and increase systemic toxicity and use is contraindicated. Colors the urine brown.

Question 7

metronidazole (flagyl)

Answer 7

Metronidazole is a prodrug that is transformed to a highly reactive nitro radical anion in susceptible organisms (i.e., protozoa and anaerobic bacteria with a sufficiently negative redox potential). The anion kills these organisms by radical-mediated mechanisms that target DNA (strand breaks and / or inhibition of DNA replication.) This is a bactericidal mechanism of action.

Question 8

metronidazole uses

Answer 8

anaerobes– C. difficile, C. perfringens, B. fragilis

protozoans– giardia, amoeba, trichomonas