Description

Asymptomatic bacteriuria (ASB) is specific bacterial growth of ≥10⁵ CFU/mL in one and two consecutive midstream urine samples for men and women, respectively >18 years. This definition applies to individuals with no clinical symptoms.

Epidemiology

Incidence

• Premenopausal females: 1–6%
• Pregnancy: 2–10%
• Older females and males: 4–19%
  • ~22% of women >90 years old (1)
• Institutionalized older population: 15–50%

Prevalence

• Variable; increases with age, female gender, sexual activity, neurogenic bladder, and presence of genitourinary (GU) abnormalities
• Pregnancy: 2–10%
• Short- and long-term indwelling catheter 9–23% and 100%, respectively
• Long-term care residents in women 25–50% and men 15–40%

Etiology and Pathophysiology

• Pathophysiology: Most cases are secondary to the ascension of bacteria from the urethra to bladder.
• Microbiology is similar to that of other urinary tract infections (UTI), with bacteria originating from the periurethral area, vagina, or gut.
• Organisms are less virulent in ASB than those causing UTI.
• The most common organism is Escherichia coli. Other common organisms are Klebsiella pneumoniae, Enterobacter, Proteus mirabilis, Staphylococcus aureus, group B Streptococcus (GBS), and Enterococcus.

Genetics
Genetic variations that reduce toll-like receptor-4 (TLR4) function have been associated with ASB by lowering innate immune response and delaying bacterial clearance.

Risk Factors

• Pregnancy
• Older age
• Female gender
• Sexual activity, use of diaphragm with spermicide
• GU abnormalities: neurogenic bladder, urinary retention, urinary catheter use (indwelling, intermittent, or condom catheter), or pathologic urinary fistulas
• Institutionalized elderly population
• Diabetes mellitus
• Immunocompromised status
• Spinal cord injuries or functional impairment
• Hemodialysis

Commonly Associated Conditions

Depends on the risk factors