A 16-year-old pregnant adolescent has been treated for acute cystitis. To determine the effectiveness of therapy with nitrofurantoin (Macrobid), the nurse practitioner instructs the adolescent to return for a urine culture:

Rationale: A. Testing 1–2 weeks after starting therapy is premature, as the full course of antibiotics has not yet been completed, and results may not accurately reflect treatment effectiveness. B. One week after completion of nitrofurantoin therapy is recommended to assess the resolution of bacteriuria and confirm the effectiveness of treatment for acute cystitis in pregnant adolescents. This timing allows any remaining bacteria to be detected while minimizing false negatives. C. Testing after 10 days of therapy initiation may still be during treatment, which is too early to confirm eradication. D. Waiting 2 weeks after completion of therapy is not necessary; 1 week post-treatment is sufficient to evaluate effectiveness and ensure prompt follow-up.