Urinary tract infections in the catheterized elderly: Change in bacteriurial flora as a risk factor.

Abstract

Indicators of acute urinary tract infection (UTI) in the catheterized elderly are few: patients often cannot communicate symptoms and may fail to show a fever; polymicrobial colonizing flora and WBCs are nearly universal with the presence of a catheter, complicating laboratory diagnosis. A prospective study was undertaken to increase understanding of the dynamics of acute UTI and to explore the hypothesis that change in bacteriurial flora contributes to acute UTI in this population. For this study, acute UTI was defined as a culture positive with at least one organism at concentrations of greater than 1,000 org/ml, and significant change in the character of the urine (e.g., hematuria) or diagnosis by a physician or fever of equal to or greater than 38$\sp\circ$C unrelated to other causes. Weekly urine samples were obtained for six months from 13 chronically catheterized elderly and cultured to demonstrate all organisms in counts greater than 1,000 organisms/ml. Occurrence of a new organism in culture one week before or the same week as acute UTI was weakly but not significantly statistically associated with acute UTI (RR = 1.5 (95%CI 0.60 to 3.71)). Presence of crystals in urine was strongly associated with an increased risk of death the same week (RR = 47.4 (95% CI 4.86 to 462.89)). Recovery of Proteus mirabilis from urine culture was also strongly associated with risk of death the same week (RR = 26.3 (95% CI 1.79 to 43.98)). Hematuria functioned well in this sample as an indicator of acute UTI but needs to be confirmed in further controlled studies. The role of new organisms in the development of acute UTI, especially those organisms known to have an established potential for pathogenicity in the urinary tract such as Escherichia coli and Staphylococcus aureus, deserves further study. The strong association between death and the recovery of Proteus mirabilis suggests this agent has a high pathogenic potential unique to the urinary tract of the chronically catheterized, possibly due to urease-induced crystal formation. Proteus-dependent and patient-dependent variables in the formation of catheter-obstructing crystals requires further study.