Influence of various criteria for elimination of duplicates when calculating the prevalence and antibiotic susceptibility of microorganisms associated with urinary infections.

The effect of applying various criteria for elimination of repeated isolates in the same patient on the prevalence and antibiotic susceptibility of microorganisms frequently associated with urinary infections were analyzed. When time criteria were applied, there was a decrease in the number of isolates of 13.4-27.5%, whereas when variations in antibiotic susceptibility were considered, between 4.3 and 20.3% of the isolates were eliminated. The absolute number of isolates varied considerably depending on which of these two criteria were used, but neither criterion was seen to modify significantly the antibiotic susceptibility of these microorganisms and this confirms the recommendations of the NCCLS for this group of pathogens.