Antibiotics for asymptomatic bacteriuria prolong hospitalization with no clinical benefit

Antibiotic treatment of asymptomatic bacteriuria (ASB) does not improve clinical outcomes and leads to longer hospitalization among inpatients, according to a retrospective cohort study.

“We found high treatment rates of ASB in hospitalized patients and identified patient characteristics associated with antibiotic treatment of ASB [such as older age and dementia],” said the researchers.

“[In addition], no benefit associated with ASB treatment in the hospitalized patient was identified, but potential harm includes an association with longer duration of hospitalization,” they said, calling for interventions to prevent inappropriate antibiotic treatment in elderly, hospitalized patients.

The study, conducted at 46 hospitals in Michigan, US, involved 2,733 hospitalized adults (median age 77 years, 78.2 percent female) who were diagnosed with ASB following a positive urine culture without signs or symptoms of urinary tract infection (UTI). Of these, 82.7 percent (n=2,259) received antibiotic treatment* for a median 7 days, with ceftriaxone the most frequently prescribed antibiotic at treatment onset (61.6 percent) and fluoroquinolones the most frequently prescribed at discharge (33.2 percent).

Escherichia coli (E. coli) and Klebsiella species were the most commonly isolated pathogens from urine culture (50.2 and 15.3 percent, respectively).

About 39 percent of patients had diabetes, 20.5 percent had dementia, 41.6 percent had chronic kidney disease, and 13.7 percent had an indwelling urinary catheter.

The likelihood of receiving antibiotic treatment for ASB increased with age (odds ratio [OR], 1.10 per 10-year increase, 95 percent confidence interval [CI], 1.02–1.18; p=0.01) and among those with urinary incontinence (OR, 1.81, 95 percent CI, 1.36–2.41; p<0.001), dementia (OR, 1.57, 95 percent CI, 1.15–2.13; p=0.004), or acute altered mental state (AMS; OR, 1.93, 95 percent CI, 1.23–3.04; p=0.004). [JAMA Intern Med 2019;doi:10.1001/jamainternmed.2019.2871]

Patients with peripheral leucocytosis (white blood cell [WBC] count >10,000 cells/μL; OR, 1.55, 95 percent CI, 1.21–2.00; p<0.001), E. coli bacteriuria (OR, 1.42, 95 percent CI, 1.12–1.79; p=0.003), positive urinalysis (detection of leukocyte esterase or nitrite or >5 WBCs per high-power field; OR, 2.83, 95 percent CI, 2.05–3.93; p<0.001), or urine culture (≥100,000 colony-forming units per high-power field; OR, 2.30, 95 percent CI, 1.83–2.91; p<0.001) were also more likely to receive treatment for ASB.

Likelihood of death (p=0.35), readmission (p=0.14), emergency department visit (p=0.52), discharge to post-acute care facility (p=0.22), and Clostridioides difficile infection (p=0.86) within 30 days of hospital discharge did not differ between patients who did and did not receive antibiotics.

Patients who received antibiotics were hospitalized for a longer period following urine test** than those who did not receive antibiotics (median 4 vs 3 days, relative risk, 1.37, 95 percent CI, 1.28–1.47; p<0.001).

“These findings support guideline recommendations against ASB treatment among hospitalized patients and suggest potential harm associated with treatment,” said the researchers.

The factors identified as associated with increased likelihood of treatment are common among elderly patients. Coupled with an elevated risk of antibiotic-related adverse events, this age group is at especially high risk of inappropriate antibiotic treatment, they said.  

In this study, abnormal urinalysis was the most common cause (42.6 percent) of indication for urine culture. While a negative urinalysis “makes a UTI unlikely”, a positive urinalysis does not necessarily signal a UTI or call for antibiotic therapy, said the researchers.

“Given the high prevalence of both pyuria [91.4 percent] and ASB in this population, reflex urine culturing may potentially further contribute to inappropriate antibiotic use in hospitalized elderly patients. [D]iagnostic stewardship interventions and education should emphasize the poor positive predictive value of abnormal urinalysis results and emphasize symptoms as the correct prompt for urine testing and UTI diagnosis,” they said.

However, they acknowledged that prompt antibiotic therapy may be warranted in some cases, using qSOFA*** score as a guide, for instance.