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.

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

Pregnant women Regimen:3-7 day for any of the following ▸ Amoxicillin 250 mg–1 gm po tid OR Oral cephalosporins Cefaclor500 mg po q8h or 500 mg extended release q12h Cefdinir 300 mg po q12h or 600 mg po q24h Cefditoren 200 mg tabs—2 tabs bid Cefixime 400 mg po q24h Cefpodoxime proxetil 200 mg po q12h Cefprozil 500 mg po q12h Ceftibuten 400 mg po q24h Cefuroxime axetil 250 or 500 mg q12h Loracarbef 400 mg po q12h OR ▸ TMP-SMX 50 mg/kg IV q8h OR ▸ Trimethoprim 2.5 mg/kg IV q12h 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. Diabetic Women Asymptomatic bacteriuria screening or treatment is not recommended for diabetic women. No change in the rate of symptomatic urinary tract infection, diabetes progression and complication or overall mortality in diabetic women, in addition to the adverse effects of antimicrobial therapy. Older Persons Residing in the Community Routine screening and treatment for asymptomatic bacteriuria is not indicated. Treatment has no effect on decreasing symptomatic urinary tract infections. Elderly Institutionalized Subjects No recommendation for screening for or treatment of asymptomatic bacteriuria. Instead, treatment has increased the risk of adverse effects and reinfections with resistant strains. Subjects with Spinal Cord Injuries No benefit from screening for or treatment of asymptomatic bacteriuria Although the high prevalence of asymptomatic bacteriuria in patients with spinal cord injuries, but antimicrobial therapy harm outweigh benefit because of recurrent infections with more resistant strains.. Patients with Indwelling Urethral Catheters It is not recommended to screen for or treat asymptomatic bacteriuria or fungiuria, but antimicrobial therapy can be used for women with persistent bacteriuria 48 hours after removal of the urethral catheter. No benefit of therapy of asymptomatic bacteriuria due the high recurrence rates with more resistance to antibiotics. Significant improvement has been shown with women treated for bacteriuria that existed 48 hours after removal of indwelling urethral catheters. Urologic Interventions Due to high risk of bacteremia (60%) and sepsis(6-10%) because of traumatic genitourinary procedures, and the effectiveness of antimicrobials to prevent such complications; screening for bacteriuria and antimicrobial therapy is recommended before the initiation of invasive urologic procedures like transurethral resection of prostate. Antibiotic therapy usually discontinued after the procedure, unless there is an indwelling urethral catheter until removed. Immunocompromised Patients and Other Patients Poor transplant prognosis and complications hasn't been associated with asymptomatic bacteriuria, so there is no benefit from screening for and treatment of asymptomatic bacteriuria in renal transplant or other solid organ transplant patients. References