If the urine was sent off for a culture, it can be determined whether it was resistant to the antibiotic or not. If is was resistant to the Bactrim (the likely sulfur-based antibiotic) then another antibiotic (i.e. Cipro) can be tried.
You can consider repeating the urine sample if the symptoms are still continuing, or discuss whether a referral to a urologist is necessary if the symptoms are not improving.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
http://www.straightfromthedoc.com