A New Patient Comes to See the Primary Care NP

A new patient comes to see the primary care NP with fever,mild dehydration,and dysuria with flank pain.The patient tells the NP that a previous provider always prescribed trimethoprim-sulfamethoxazole and wonders why a urine culture is necessary because this antibiotic has worked in the past.The NP should tell this patient that a culture is necessary to help determine:

A) the correct dose of the antibiotic.
B) whether antibiotic resistance is occurring.
C) whether multiple organisms are causing infection.
D) the length of antibiotic therapy needed to treat the infection.