Current microbiological and clinical aspects of urinary tract infections

To evaluate some risk factors which could affect the isolation rates of various uropathogens and their in vitro susceptibility to antibiotics in ambulatory and hospitalized patients.

A prospective study was conducted in a microbiological laboratory at Pisa Hospital. Nine-hundred and seventy-two consecutive patients with documented urinary tract infection were enrolled from April 1996 to October 1999. Data on age, sex, current or previous bladder catheterization, some underlying diseases as diabetes mellitus, and previous antibiotic therapy were recorded. The distribution of bacteria isolates and their in vitro susceptibility to antibiotics was evaluated.

Escherichia coli was responsible for 54.7% of urinary tract infections. Isolation of E. coli is decreasing in comparison to previous observations, especially in males and in patients with indwelling bladder catheters who instead show higher Pseudomonas spp. and Enterococcus spp. isolation rates than females and non-catheterized patients. Diabetes mellitus does not affect the isolation rate of uropathogens and their patterns of susceptibility. Multivariate analysis of multiresistant uropathogens showed a positive significant correlation with indewelling bladder catheter and age. An upward trend in the resistance of E. coli to cotrimoxazole, ampicillin and fluoroquinolones was observed from 1996 to 1999; more than 50% of Pseudomonas spp. strains were resistant to fluoroquinolones and gentamicin.

The empirical antibiotic therapy of patients with urinary tract infection should be guided by an accurate anamnesis evaluating not only age and sex but also the presence of a bladder catheter at the moment of urine collection or a history of recent bladder catheterization and previous courses of antimicrobial drugs.