Asymptomatic bacteriuria

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Asymptomatic bacteriuria is a condition in which a significant number of bacteria appear in the urine occurring without typical symptoms such as burning during urination or frequent urination.

Diagnostic Criteria

The diagnostic criteria depend on the way the urine specimen is being sampled, the goal is to avoid contamination and limit the period between taking the sample and testing it (avoidance of false positivity due to bacterial growth).

Clean catch, midstream voided urine specimen

For asymptomatic women:two consecutive voided urine specimens with the same bacterial strain isolated in a quantitative count of ≥10⁵cfu/mL.
For asymptomatic men :a single clean catch voided urine specimen with 1 bacterial species strain isolated in a quantitative count of ≥10⁵cfu/mL.

OR

Bladder catheterization

A single catheterized urine specimen with isolation of species of bacterial strain in a quantitative count of ≥100 cfu/mL in both men and women.

Presumptive Etiologies

Most common organism

Escherichia coli is the single most common cause of asymptomatic bacteriuria.
Patients with abnormal genitourinary tract or institutionalized elderly:

E.Coli remain common cause, but in men Proteus mirabilis is more common in men.
Long term urologic device in place
Polymicrobial including Pseudomonas aeruginosa,P. mirabilis, Providencia stuartii, and Morganella morganii (urease-producing organisms).

Other organisms

• Coagulase-negative staphylococci especially in men .
• Enterococcus species.
• Group B streptococci

• Gardnerella vaginalis.

Management

Premenopausal, Nonpregnant Women

No screening or treatment recommended for healthy, bacteriuric women.
Although asymptomatic bacteriuria increases the risk of urinary tract infection but has no effect on the long term adverse outcomes like CKD, genitourinary cancer or overall survival. Studies' results indicated that the treatment wouldn't decrease the frequency for asymptomatic bacteriuria or the risk of developing symptomatic urinary tract infection.

Pregnant Women

In early pregnancy, screening for asymptomatic bacteriuria by urine culture and treatment of positive results are recommended.

• Antibiotics treatment has shown a significant decrease in the risk of subsequent pyelonephritis(from 25-30% to 1-4%). It also reduce the frequency of preterm deliveries and low birth weight.
• The duration of antimicrobial therapy is 3-7 days.
• After therapy of recurrent bacteriuria, periodic screening should be considered.