Microbiology of urinary tract infections in ambulatory patients. Therapeutic options in times of high antibiotic resistance

Objective. To determine the antibiotic resistance of urinary pathogens in ambulatory patients from Mexico City, in order to infer therapeutic options in environments of high resistance. Methods. Cross sectional survey performed between July 2006, and January 2007, in patients 2 3 year-old from a private institution. Cultured organisms were identified with a commercial biochemical system. For common antibiotics, susceptibility was performed by broth microdilution with a commercial system; for fosfomycin tromethamine, the disk diffusion test was performed. Results. From 1685 urine specimens, 257 (15.3%) yielded a positive culture, 215 (83.7%) from women and 42 (16.3%) from men. Global resistance was the following: ampicillin, 68.4%; co-amoxiclav, 19.5%; ciprofloxacin, 36.3%; cephalothin, 64.7%; ceftriaxone, 12.2%, cefuroxime, 18.7%; nitrofurantoin, 19%; trimethoprim-sulphamethoxazol, 53.4%; gentamicin, 18.9%, and fosfomycin tromethamine, 0.8%. Escherichia coli was the main pathogen, with 203 (79%) isolations; its specific resistance was similar to the global one, and its production of extended-spectrum beta-lactamases (ESBLs) was 9.4%. Conclusions. The high resistance rate found is alarming; we have few options for the initial treatment of urinary tract infections in ambulatory patients. To control the problem, health authorities must regulate the indiscriminate use of antibiotics.