Amoxicillin therapy of acute urinary infections in adults.

Fifty-two patients, 48 females and 4 males, with suspected urinary infection were treated with amoxicillin. Twenty-two females with presumed bladder infection were treated with amoxicillin, 250 mg three times a day for 7 days; 26 females and 4 males with presumed renal infection were treated with amoxicillin, 500 mg three times a day for 14 days. Five patients were immediate treatment failures, with positive urine cultures during therapy. All five patients had been infected with amoxicillin-resistant urinary pathogens. Three patients, treated as for bladder infections, reinfected during 6 weeks of follow-up, and only one relapsed. Two patients, treated as for renal infections, reinfected, whereas four relapsed. During therapy, amoxicillin-susceptible gram-negative rods were eradicated from the periurethral area in all but one patient. Of 28 patients studied, 19 acquired a predominant growth of either resistant aerobic gram-negative rods or Candida albicans from periurethral cultures. Our findings suggest that these two regimens of amoxicillin achieve satisfactory cure rates in urinary infection, but both regimens significantly alter the normal periurethral flora.