Asymptomatic bacteriuria in critical-access hospitals: Prevalence and patient characteristics driving treatment

We evaluated the prevalence and treatment of asymptomatic bacteriuria (ASB) in 17 critical-access hospitals. Among 891 patients with urine cultures from September 2021 to June 2022, 170 (35%) had ASB. Also, 76% of patients with ASB received antibiotics for a median duration of 7 days, demonstrating opportunities for antimicrobial stewardship.


Results
We reviewed the data for 1,087 patients with urine cultures; the median number of cases submitted per CAH was 45 (IQR, 34-90).Among the patients identified, 891 (82%) were included.Exclusions were due to treatment for concomitant bacterial infections (n = 106), missing data (n = 65), age <18 years (n = 17), and pregnancy (n = 8).Overall, 75% were female, and the median age was 69 years.The emergency department (ED) was the most common location for urine culture collection (72%).Also, 75% of urine cultures originated from positive urinalysis results reflexing to culture.Baseline characteristics are summarized in Table 1.
Among 486 patients with a positive urine culture, 170 (35%) had ASB, and 129 (76%) received antibiotics.We detected a higher proportion of older age, male, urological comorbidities, and acute mental status changes among those treated for ASB.Among the 129 patients with ASB treated with antibiotics, oral agents were prescribed for 105 (81%).Moreover, β-lactams (45%) were most frequently prescribed, followed by nitrofurantoin (19%) and Infection Control & Hospital Epidemiology fluoroquinolones (18%) (Table 2).Of the 55 patients who received intravenous therapy, 98% received a β-lactam.The median antibiotic duration was 7 days (IQR, 3-7).Also, 95% of patients treated for ASB had a positive urinalysis that resulted in a reflex to culture.Among 405 patients with a urine culture showing <100,000 CFU/mL of bacterial growth (including those with no growth), 160 (40%) had no documented signs or symptoms of UTI.More than half (59%) were treated with antibiotics for a median duration of 7 days (IQR, 3-7).

Discussion
To our knowledge, this study is the largest to evaluate the prevalence and treatment of ASB in CAHs.Importantly, 35% of patients with a positive urine culture had no documented UTI-related symptoms.
Although the prevalence of ASB is notably lower in our study compared to previous reports (45%-71%), 75% of patients were inappropriately prescribed antibiotics for ASB. 3,6,77][8] Although a growing body of evidence demonstrates the lack of clinical benefit with treatment of ASB, more concerning are the underrecognized data suggesting potential harm. 2 Curren et al 9 found that each day of antibiotic therapy was associated with 4% increased odds of experiencing an adverse drug event (ADE).Notably, 19% of ADEs have been attributed to antibiotic regimens that were not clinically indicated, most commonly because of treatment of ASB. 9 In our study, the median duration of therapy was 7 days (IQR, 3-7) among treated ASB patients, which exceeded guideline recommendations for cystitis. 10ven for those patients with ASB who are inappropriately treated, the potential for antibiotic-associated harm could be reduced through decreased duration of therapy. 3,9,10n our study, most urine cultures was collected in the EDs of CAHs.Thus, EDs represent a high-yield location for stewardship interventions because urine culture is often ordered before initiating a symptom-driven workup as a triage to optimize ED throughput. 11In our study, almost half of the patients with ASB were discharged directly from the ED, which limits opportunities to re-evaluate appropriateness of therapy as new data become available, including urine culture results.Therefore, ED workflows are a particularly important target for ASB interventions in CAHs.
Interestingly, nearly 60% of asymptomatic patients received treatment despite urine cultures showing <100,000 CFU/mL of bacterial growth or no growth.We postulate that the strict definition of ASB undercaptures the overall inappropriate antibiotic prescribing.
Our study had several limitations.Given the retrospective nature of the study and lack of case selection standardization among sites, there was a potential for bias in the selection of patients across the spectrum of care in both ambulatory and hospital settings.Identification of abnormal urinalyses and criteria to reflex a urinalysis to culture varied from institution to institution.Duration of therapy was based on written prescriptions; therefore, we were not able to confirm whether the antibiotic course was completed or was subsequently discontinued.Lastly, there was an overrepresentation of cases from some sites and insufficient representation from others.
In summary, similar to the well-described overtreatment of ASB in larger, urban, academic hospitals, inappropriate treatment of ASB is common in CAHs, especially in their EDs.Unnecessary antibiotic use in patients with ASB and long duration of therapy in treated patients are important areas for stewardship interventions in the CAH setting.

Table 2 .
Antibiotic Prescribing among Patients without Urinary Symptoms Received any oral therapy includes during hospitalization, at discharge, or in the outpatient setting.