Use of time-trend analysis in the design of empirical antimicrobial treatment of urinary tract infection.

Selection of empirical treatment of hospitalized patients with urinary tract infection (UTI) is usually based on the results of urine culture as obtained from the local microbiology laboratory. In order to improve the precision and reliability of traditional methods, we analyzed temporal changes in the results of urine culture and antibiograms and stratified the results by inpatient department and the presence/absence of an indwelling catheter. The database consisted of urine cultures obtained during the first 3 months of each year over a 10-year period between 1991 and 2000. Only urine samples that grew a single organism at a concentration of >105 cfu were included in the analysis. Trend statistical tools, readily available but thus far not used for microbiological analyses, were applied to assess the decay in activity of individual antibiotic agents over time and to calculate susceptibility rates of organisms in subsets of urine samples. Organisms, antimicrobial susceptibility rates and the degree of decay in antimicrobial susceptibility rates varied significantly according to the location of the patient in the hospital and the presence of an indwelling catheter. Stratified trend analysis is a useful tool that can be helpful in designing and adapting clinical guidelines for the selection of appropriate empirical antibiotic treatment for the individual patient with urinary tract infection.