Treating urinary-tract infections: which antibiotic?

Family physicians often start antibiotic treatment for urinary-tract infections (UTI) before they have a urine-culture report. Which is the most appropriate antibiotic to prescribe in this situation? The author of this study reviewed a random sample of charts in a rural Newfoundland clinic and analysed results of urine-culture and sensitivity reports. Certain conclusions were based on the infecting organisms' sensitivity to the various antibiotics and on the cost of the antibiotics. In particular, it would seem that ampicillin is of very limited value in treating urinary-tract infections, and the most appropriate antibiotic for treating a UTI when the culture result is not known is a trimethoprimsulfamethoxazole combination.