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

BK polyomavirus-specific 9mer CD8 T cell responses correlate with clearance of BK viremia in kidney transplant recipients: first report from the Swiss Transplant Cohort Study

BK polyomavirus (BKPyV) causes premature kidney transplant (KT) failure in 1-15% of patients. Because antivirals are lacking, most programs screen for BKPyV-viremia and, if positive, reduce immunosuppression. To evaluate the relationship of viremia and BKPyV-specific immunity, we examined prospectively cryopreserved plasma and peripheral blood mononuclear cells at the time of transplantation (T0) and at 6 mo (T6) and 12 mo (T12) after transplant from 28 viremic KT patients and 68 nonviremic controls matched for the transplantation period. BKPyV IgG seroprevalence was comparable between cases (89.3%) and controls (91.2%; p = 0.8635), but cases had lower antibody levels (p = 0.022) at T0. Antibody levels increased at T6 and T12 but were not correlated with viremia clearance. BKPyV-specific T cell responses to pools of overlapping 15mers (15mer peptide pool [15mP]) or immunodominant CD8 9mers (9mer peptide pool [9mP]) from the early viral gene region were not different between cases and controls at T0; however, clearance of viremia was associated with stronger 9mP responses at T6 (p = 0.042) and T12 (p = 0.048), whereas 15mP responses were not informative (T6 p = 0.359; T12 p = 0.856). BKPyV-specific T cells could be expanded in vitro from all patients after transplant, permitting identification of 78 immunodominant 9mer epitopes including 50 new ones across different HLA class I. Thus, 9mP-responses may be a novel marker of reconstituting CD8 T cell function that warrants further study as a complement of plasma BKPyV loads for guiding immunosuppression reduction