*Purpose: Asymptomatic bacteriuria (ASB) is the presence of bacteriuria with no symptoms. Recent guidelines recommend against treatment of ASB in kidney transplant (KT) recipients more than 2 months post-transplant. These recommendations stem from clinical studies that have demonstrated minimal effect on graft function and low risk of progression to symptomatic urinary tract infection (UTI) if ASB is untreated. The risk of unnecessary antibiotic exposure may exceed the potential treatment benefits. The purpose of this study is to evaluate trends in treatment and clinical outcomes in KT recipients with ASB. In addition, current literature and guidelines only address urine culture growth of > 10^5 CFU/mL and this study aimed to broaden that definition to include urine culture growth of > 10^4 CFU/mL.

*Methods: This was a retrospective chart review that included all patients 18 years and older with a KT at our institution between 1/20/2016 and 2/28/2019. Patients with multi-organ transplantation were excluded. The primary endpoint was the incidence of at least 1 episode of ASB between 2-12 months post-KT. ASB was defined based on two different yields of urine culture growth, ≥10^4 CFU/mL (noted as total ASB) and ≥10^5 CFU/mL (noted as guideline concordant (GC) ASB) with no symptoms. Secondary endpoints, evaluated for all ASB episodes, include treatment rate, progression rate to symptomatic UTI, ASB treatment agent and duration, and development of resistance (6 months from treated ASB). Graft function and patient survival were also assessed.

*Results: 134 KT recipients were included. Incidence of at least 1 episode of ASB (per patient) for total and GC ASB was 29% and 16%, respectively. Treatment rates of total ASB and GC ASB cultures were 40% and 64%, respectively. Fluoroquinolones were the most common agents prescribed (61.7% of treated cultures). The median treatment duration of an ASB episode was 10 days. Progression rate of untreated ASB episodes to symptomatic UTI was 7.7% and for treated ASB episodes was 11.8% (P=0.71). Antibiotic resistance developed in 7.7% of treated cultures. Graft function was similar between the ASB population and the non-ASB population, with a median serum creatinine of 1.4 mg/dL for both groups at 12 months post-KT. Mortality was similar in both groups.

*Conclusions: Overall, this study found that prescribers chose to treat 40% of ASB episodes, including cultures with less CFU/mL than the GC definition. With a low incidence of progression to symptomatic UTI identified and no difference in graft function, this study supports the guideline recommendations to routinely refrain from treatment of ASB episodes. Future studies are needed to further explore the association of treatment of ASB and development of antimicrobial resistance.

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