*Purpose: Asymptomatic bacteriuria (ASB) occurs in nearly 50% of kidney transplant recipients (KTRs) in the first year post-transplant. Data evaluating the risk of untreated ASB on progression to symptomatic urinary tract infection (UTI) and allograft outcomes remains limited. Thus, antibiotics are often prescribed in this population. The purpose of this study was to evaluate the impact of antibiotic treatment for ASB on outcomes in KTRs.

*Methods: In this single-center, retrospective cohort study of adult KTRs between January 2009 and August 2015, patients who received antibiotics for the treatment of ASB were compared to those with untreated ASB. Patients with urostomies, indwelling catheters, nephrourteral stents, perinephric abscesses, urosepsis, and those requiring intermittent catheterization were excluded. The primary outcome was a composite of symptomatic cystitis and pyelonephritis. Secondary endpoints included allograft-related outcomes.

*Results: Of 150 included KTRs with ASB, 57% were prescribed antibiotics. The median age of the entire cohort was 55 and majority were females (62.7%). Other baseline characteristics were similar between the two groups except more patients in the treated group had a living unrelated kidney transplant (26.6% vs. 12.8%, p=0.04), and more patients in the untreated group had glomerulonephritis as their indication for transplant (10.5% vs 1.6%, p=0.04). ASB commonly occurred within the first month post-transplant (median time to index ASB case, 23 days). Antibiotic treatment was more common in KTRs with urine cultures having CFU > 10⁵ (80.2% vs. 45.3%, p <0.01). No difference in the primary composite outcome was observed among KTRs treated with antibiotics for ASB versus those left untreated (14% vs. 18.8%, p=0.50). Additionally, no significant differences in secondary outcomes were seen (Table 1). Among KTRs with ASB who were treated with antibiotics, a median of 7 days was prescribed and de-escalation to a narrower spectrum agent was possible in 45.3% of patients.

*Conclusions: KTRs with untreated ASB have similar outcomes as those prescribed antibiotics, even in the early post-transplant period. Our findings suggest a role for antimicrobial stewardship by discouraging antibiotic use in this population.

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