[Evolution of Escherichia coli antibiotic resistances in urine samples from the community]

The objectives of this work are two: first, to evaluate the resistance of Escherichia coli to several antibiotics and their trends over a six-year period in strands isolated in urine samples from patients receiving health-care in general practitioner offices in our environment; and second, to evaluate if empirical treatment regimens commonly accepted in our country would be applicable in our environment depending on the results of this study.

We analyzed the urine cultures positive for Escherichia coli obtained from samples collected at the 10 primary health care centers of the health-care area of El Bierzo and Laciana (Leon, Spain) between the years 2002 and 2007. In vitro resistances of these germs to several common use antibiotics were determined: fosfomycin, nitrofurantoin, tobramycin, cefuroxime, cefixime, amoxicillin-clavulanic acid, cotrimoxazole, ciprofloxacin, norfloxacin, and ampicillin. The existence of statistically significant (p < 0.05) differences in sensitivity comparing the years 2002 and 2007, including all antimicrobials except cefixime, was analyzed by the chi-square test. For cefixime we compared the results between 2002 and 2005.

An increase of the resistance of Escherichia coli isolated in urine to all antimicrobials under study has occurred, except for nitrofurantoin, being the differences statistically significant in most cases. Nevertheless, resistances to fosfomycin and nitrofurantoin have remained below 6% throughout the study period. Resistances to tobramycin and cefuroxime were slightly over 10% and cefixime below 3.4%, although in the last one we only have data until 2005. Resistances to amoxicillin-clavulanic acid, initially low, have progressively increase reaching 20.6% in 2007. The same has happened for cotrimoxazole, ciprofloxacin, norfloxacin and ampicillin, passing 32% in 2007 in the first three cases and 62% in the last one.

Variations in bacterial resistance patterns for Escherichia coli obliges to have an updated knowledge of them to adapt general empirical treatment uses to each specific health-care area.