The answer is E. Ciprofloxacin for 4 weeks
Acute bacterial prostatitis in a non-toxic outpatient is treated with a fluoroquinolone or trimethoprim-sulfamethoxazole for a prolonged course — here, ciprofloxacin for 4 weeks. Two things drive that answer, and both are testable: which drugs actually penetrate prostate tissue, and how long you have to treat.
Penetration is the whole point. The prostate is a lipid-rich, relatively acidic compartment behind a capillary-epithelial barrier, and only lipophilic agents that are weak bases cross it in useful concentrations — which is why fluoroquinolones and TMP-SMX are first line and why most beta-lactams are not. Acute inflammation does transiently increase penetration, but the choice of agent still follows the tissue pharmacology, not the urine culture alone. Duration is the second half. A 3- to 7-day course, appropriate for uncomplicated cystitis, badly undertreats the prostate and invites relapse and progression to chronic bacterial prostatitis; published guidance runs roughly 2 to 6 weeks, and 4 weeks is a standard target with a follow-up culture to confirm clearance.
Note that TMP-SMX is an equally acceptable first-line choice and is deliberately absent from the options so the question has one best answer; in practice the pick between them is driven by local resistance, culture data, and the fluoroquinolone class warnings regarding tendinopathy, neuropathy, and aortic events. The organisms are the usual gram-negative uropathogens — E. coli most commonly, then Proteus, Klebsiella, and Pseudomonas, with Enterococcus among gram positives; in sexually active men under 35, cover N. gonorrhoeae and C. trachomatis instead. Admit for intravenous therapy if the patient is septic, immunocompromised, unable to tolerate orals, in urinary retention, or has a suspected prostatic abscess. And remember the exam caveat this stem builds in: examine the prostate gently and avoid vigorous massage, which can provoke bacteremia.
Sorting the distractors: nitrofurantoin is the trap and the highest-yield wrong answer — it is excellent for uncomplicated cystitis because it concentrates in urine, but it achieves essentially no useful tissue concentration and is explicitly inadequate for prostatitis; cephalexin is a beta-lactam with poor prostatic penetration, and 7 days is far too short regardless; single-dose fosfomycin is a uncomplicated-cystitis regimen in women and cannot treat an invasive tissue infection in a single dose; and azithromycin covers atypicals but not the gram-negative uropathogens that cause the great majority of acute bacterial prostatitis, and 5 days is far too short.
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