Single-dose therapy in management of urinary tract infection.

A study was undertaken to determine whether single dose therapy for urinary infection can identify those patients who are likely to have underlying pathological changes of the renal tract, and, thus, those patients who need further investigation. Fifty-three patients (50 females, three males) with documented recurrent urinary tract infection, in whom the present infection was confirmed in two consecutive urine specimens, were studied. Patients received a single dose of 0.5 g kanamycin intramuscularly (or another antibiotic for kanamycin-resistant organisms), and urine was cultured daily over the following week. The original infecting organism was eradicated in 22 of the 37 patients (60%) who completed the study (urine clear at one week), but persisted or relapsed in 15. Bacteriuria disappeared within 24 hours in all but four patients, but both relapses and new infections were seen as early as 48 hours after treatment. Fifteen of 18 patients (83%) with radiologically normal renal tracts were successfully treated compared with only 6 of 16 patients (37%) with a radiological abnormality. Failure of single dose therapy to eradicate urinary infection is thus an indication for further investigation.