Bacteriology of urinary tract infection associated with indwelling J ureteral stents

Abstract

Purpose: To investigate the microorganisms responsible for urinary tract infection (UTI) and stent colonization in patients with indwelling J ureteral stents and to compare the antimicrobial susceptibility pattern of the isolates from urine and J stents in order to establish the etiologic agents of bacteriuria and colonized stents in such patients and provide baseline data on an antibiotic policy for the urology unit.

Patients and methods: Midstream urine from 250 patients requiring J stent insertion was investigated microbiologically prior to stent insertion and on the day of stent removal. After stent removal, 3 to 5 cm of the tip located in the bladder was also sent for culture. Patients' bio-data and underlying diseases were documented. Those with no known systemic diseases ("normal patients") were also studied as controls. Of the 250 patients studied, 152 (61%) were normal, while 27 (11%), 53 (21%), and 18 (7%) had diabetes mellitus (DM), chronic renal failure (CRF), and diabetic nephropathy (DN), respectively. The mean duration of stent retention was 27 days. All microbial isolates were tested for their susceptibility to a panel of 10 antibiotics.

Results: Twelve patients (5%) before stent insertion and 42 patients (17%; P < 0.001) on the day of stent removal had positive urine cultures. One hundred four stents (42%) were culture positive. Of the 104 patients with positive stent cultures, in 62 patients (60%), urine culture was sterile. The commonest isolates were Escherichia coli, Enterococcus spp., Staphylococcus spp., Pseudomonas, and Candida spp. On the day of stent removal, urine culture was positive in 28% of the normal patients compared with 57% (P = 0.11), 78% (P < 0.001), and 62% (P < 0.001) of patients with CRF, DM, and DN, respectively. Stent isolates were more resistant to antibiotics than the organism isolated before stent insertion.

Conclusion: An indwelling J ureteral stent carries a significant risk of bacteriuria and stent colonization. The sensitivity of urine culture to stent colonization is low, and therefore, a negative culture does not rule out a colonized stent. Bacteria cultured from urine after stent insertion and from the stents are more resistant to antibiotics than are those cultured from urine before stent insertion. Norfloxacin or ciprofloxacin is recommended as prophylaxis prior to stent insertion, and an aminoglycoside can be added to treat symptomatic patients with severe infections.