Summary

2019 IDSA update on management of asymptomatic bacteriuria (ASB), defined as ≥10⁵ CFU/mL in urine without UTI symptoms. Updates the 2005 guideline and adds new populations (children, solid organ transplant, neutropenia, nonurologic surgery) plus guidance on interpreting nonlocalizing symptoms (delirium, falls) in older adults. Core message: do NOT screen or treat ASB except in pregnancy and before endoscopic urologic procedures involving mucosal trauma; emphasis on antimicrobial stewardship.

Key Recommendations

Do not screen for or treat ASB in infants, children, healthy nonpregnant women (pre- or postmenopausal), diabetic patients, older community-dwelling or long-term care residents, spinal cord injury patients, nonrenal solid organ transplant recipients, or patients with short- or long-term indwelling catheters.
Screen for and treat ASB in pregnant women with a urine culture at an early prenatal visit; treat for 4–7 days (not single-dose) with the shortest effective antimicrobial course.
Screen for and treat ASB before endoscopic urologic procedures that breach mucosal lining (e.g., TURP, TURBT, ureteroscopy, percutaneous stone surgery); obtain pre-procedure culture and give targeted therapy 30–60 minutes before the procedure, ideally as a single dose or 1–2 doses.
In renal transplant recipients >1 month post-transplant, do not screen or treat ASB; insufficient evidence within the first month post-transplant.
In older patients with functional/cognitive impairment, bacteriuria, and delirium or a fall but no localizing genitourinary symptoms or systemic signs (fever, hemodynamic instability), assess for other causes and observe rather than treating with antimicrobials.
If a bacteriuric older patient has fever or sepsis without localizing source, initiate empiric broad-spectrum therapy covering urinary and nonurinary sources pending cultures.
Do not screen or treat ASB before elective nonurologic surgery, including orthopedic implant procedures (rely on standard perioperative prophylaxis).
Do not screen or treat ASB before artificial urinary sphincter or penile prosthesis implantation, or in patients living with implanted urologic devices; give standard perioperative prophylaxis.
In SCI patients, recognize that UTI symptoms may be atypical (autonomic dysreflexia, spasticity, malaise, increased incontinence, cloudy/malodorous urine) — do not reflexively treat bacteriuria without such findings.
No recommendation for or against screening/treatment of ASB in high-risk neutropenia (ANC <100 cells/mm³, ≥7 days) — knowledge gap; low-risk neutropenia should be managed as nonneutropenic populations.
Avoid obtaining urine cultures in asymptomatic patients, as a positive culture drives inappropriate antimicrobial use and resistance.

Thresholds & Doses

ASB definition: ≥10⁵ CFU/mL (≥10⁸ CFU/L) of ≥1 bacterial species, irrespective of pyuria, without UTI signs/symptoms.
Pregnancy ASB treatment duration: 4–7 days (preferred over single-dose).
Pre-endoscopic urologic procedure antimicrobial timing: administer 30–60 minutes before procedure; 1–2 doses preferred over prolonged courses.
Renal transplant cutoff: >1 month post-transplant — do not screen/treat ASB; <1 month — insufficient evidence.
Short-term catheter definition: <30 days.
High-risk neutropenia: ANC <100 cells/mm³ for ≥7 days following cytotoxic chemotherapy.
Low-risk neutropenia: ANC >100 cells/mm³, ≤7 days, clinically stable.
Acquisition rate of bacteriuria with indwelling catheter: 3%–5% per catheter day.
Long-term catheter ASB prevalence: ~100%.
ASB prevalence in pregnancy: 2%–7%; in diabetic women 10.8%–16%; in long-term care women 25%–50%, men 15%–50%.

Citations

Section I (Pediatric Patients) — recommendation against screening/treating ASB in infants and children.
Section II (Healthy Nonpregnant Women) — strong recommendation against screening/treatment, moderate-quality evidence.
Section III (Pregnant Women) — screen and treat ASB; 4–7 day antimicrobial course.
Section V (Older patients with delirium/falls) — assess for other causes, do not treat ASB without localizing/systemic signs.
Section VI (Diabetes) — do not screen or treat ASB.
Section VII–VIII (Renal and nonrenal solid organ transplant) — do not screen/treat ASB >1 month post-transplant.
Section XI (Indwelling catheters) — do not screen/treat ASB for short- or long-term catheters.
Section XIII (Endourologic procedures) — screen and treat ASB prior to mucosa-breaching procedures; 1–2 doses, 30–60 min preprocedure.
Table 1 — prevalence of ASB across populations.