Outcome of treated and untreated asymptomatic bacteriuria in renal transplant recipients

Background. No guidelines exist concerning treatment of asymptomatic bacteriuria in renal transplant recipients (RTR). Because of scarce clinical symptoms and fear of complications, such episodes are frequently treated based on subjective criteria without clear clinical benefit, with the risk of selecting resistant pathogens. Methods. We retrospectively analysed the outcome of 334 asymptomatic Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) bacteriuria that occurred in 77 RTR later than 1 month post-transplantation. We distinguished: Type I, high-grade bacteriuria with pyuria; Type II, high-grade bacteriuria without pyuria; Type III, low-grade bacteriuria with pyuria and Type IV, low-grade bacteriuria without pyuria. Results. None of the 334 episodes was followed by acute rejection or chronic pyelonephritis. One hundred and one (30%) episodes were treated [32 (62%) Type I, 38 (45%) Type II, 13 (36%) Type III and 18 (11%) Type IV]. Evolution to symptomatic urinary tract infection (UTI) was similar between treated and untreated episodes (0/101 versus 4/233, P = 0.32). The four UTI resolved favourably without further complication upon treatment. Persistent asymptomatic bacteriuria occurred in 45 (46%) treated episodes (2 Type I, 27 Type II, 8 Type III and 9 Type IV), with selection of resistant pathogen in 35 cases (78%). Spontaneous bacterial clearance occurred in 138 (59%) untreated episodes (15 Type I, 23 Type II, 9 Type III and 91 Type IV). Negative control cultures tended to be more frequent in treated Type I (P = 0.09) and in untreated Type II episodes (P = 0.08). Conclusion. Restricting antibiotic treatments for asymptomatic low-grade bacteriuria and high-grade bacteriuria in the absence of pyuria, occurring later than 1 month posttransplantation, might be safe in RT