Predictive value of urinary cultures in assessment of microbial colonization of ureteral stents.

BACKGROUND AND
PURPOSE: Bacterial colonization of indwelling ureteral stents may serve as a nidus for bacteriuria in operations where stents are manipulated. The predictive value of urine cultures in the assessment of stent colonization was examined in 65 patients with indwelling ureteral stents. PATIENTS AND METHODS: Prophylactic antibiotic treatment was administered prior to stent insertion. All patients were ambulatory at the time of investigation and were examined in the outpatient clinic. Urine cultures were taken prior to stent removal after 8 to 150 (mean 64) days. The stents were removed under aseptic conditions, and the proximal and distal ends were cut off and placed in a culture medium for evaluation. None of the patients was treated for urinary tract infection prior to stent removal.
RESULTS: Bacteriuria was found in 15% of the patients. In 35 patients (54%), urine and stent cultures were sterile. In 20 patients (31%), the urine culture was sterile but the stent was colonized (Enterococcus 9, E. coli 5, Staphylococcus aureus 2, S. epidermidis 2, Candida 1, Citrobacter diversus 1). One patient had a sterile stent culture with bacteriuria. In 9 patients (13.5%), urine and stent cultures were identical (E. coli 4, Pseudomonas 4, Candida 1). The incidence of stent colonization did not correlate with stent dwelling time. The sensitivity of urine cultures for the detection of stent colonization was poor, being 31% only. In a specific patient with negative urine culture, the probability of stent colonization was 36%.
CONCLUSION: A sterile urine culture does not rule out the stent itself being colonized. Therefore, patients with indwelling ureteral stents and a sterile urine culture may benefit from prophylactic antibiotic treatment prior to endourologic procedures. The prophylactic regimen must provide coverage for common gram-negative uropathogens as well as gram-positive bacteria, including enterococci.