[Study of antibiotic multiresistance of Escherichia coli from urine cultures]

The appearance of resistance in urinary tract infections caused by Escherichia coli constitutes an important therapeutic problem that requires the study of its evolution throughout time in order to establish a suitable empirical treatment. Our objective was to test the antimicrobial sensitivity of E. coli isolations in urine cultures performed in our area.

5,247 isolates of E. coli from hospital and ambulatory urine cultures of patients in the area of Segovia were retrospectively analyzed. The antibiotic sensitivity of these isolations was studied for 4 years (2000-2005). Moreover, 6 phenotype patterns of resistance to betalactams were analyzed: natural, penicillinase, increased penicillinase, IRT, increased AMPc and BLEE and the difference in sensitivity between BLEE producing and non-producing stocks regarding nitrofurantoin, phosphomicin, ciprofloxacin, gentamicin, and trimetoprim-sulfametoxazol.

57% of isolates were resistant to ampicillin, 23% to ciprofloxacin and 31% to trimetroprim-sulfametoxazol. 48% were penicillinase producer, 6.6% increased penicillinase producer, 1.2% IRT producer, 1.1% AMPc producer and 2.2% were BLEE producer. As far as the origin of the sample is concerned, significant differences were not found. The percentages of co-resistance to ciprofloxacin and trimetoprim-sulfametoxazol were greater in BLEE producer stocks than in non-producers ones. We observed a gradual increase in the expression of this resistance mechanism throughout the studied period.

Ampicillin, ciprofloxacin and trimetoprim-sulfametoxazol are not suitable for the empirical treatment of uncomplicated urinary infections. Research on sensitivity is essential in order to establish correct empirical treatments.