Diagnosis of bacterial urinary tract infection (UTI)
Indications for Testing
When there is a clinical suspicion of UTI in patients with signs and/ or symptoms, including dysuria, frequency, flank pain, urgency.
In very young or elderly patients, the signs or symptoms might not be typical or obvious.
Special Instructions and Forms
Patient collection instructions midstream urine
1. Wash hands with soap and water.
2. Clean external genitals thoroughly with provided towelettes (Females – hold edges of labia apart and cleanse from front to back. Males – retract foreskin if not circumcised) and allow to air dry.
3. Retract foreskin or labia while urinating.
4. Void initial urine stream into the toilet.
5. Collect mid urine stream into container until half full.
6. Without touching the inside of the container and the lid, cover the container with the lid and tighten it.
7. Wash hands with soap and water.
8. Write down name, date and time of collection.
Sample should be sent to the lab for testing as soon as possible. Otherwise, keep the urine in the fridge.
The sample MUST be sent to the lab the same day of collection.
Submit specimen using the Public Health and Microbiology Specimen Collection Requisition
1. Urine culture
1. Urine culture
Aliases (clinical indications)
Urinary tract infection (UTI)
Urine in sterile container.
Container with preservative is PREFERRED. Unpreserved urine is not recommended because of bacterial overgrowth during transportation.
Specimen Minimum Volume
Automated inoculator requires at least 3mL, however manual inoculation can be performed on 1mL of urine.
|Unpreserved urine||2 hours||24 hours||Not recommended|
|Urine in preservative||48 hours||48 hours||Not recommended|
Reject Due To
|Urine collected through an indwelling catheter, or bag applied to the skin, is contaminated, and will not be cultured. Recollection using in-and-out catheterization should be recommended.|
|Nonsterile container||The lab will reject specimen in nonsterile containers. Recollection recommended.|
|Delayed in arriving to the lab for testing||Recollection recommended.|
|Repeat specimens||Repeat submission would be rejected without clinical justification.|
⃰ Rejected samples would be stored for 3 days. However, they would not be suitable for setting up for bacterial workup after 24 hours post-collection.
Urine in the bladder is normally sterile, but collection often leads to contamination with gut and skin flora. For this reason, urine culture is quantitative. Small numbers of bacteria or mixed bacterial growth (three or more different types) is more likely due to contamination. Generally, the presence of a single type of bacteria growth at high colony counts is considered a positive urine culture. However, it may represent either pathogens or contaminants.
As with all laboratory tests, the results of a urine culture should be interpreted in conjunction with other pertinent testing information, clinical signs and/or symptoms, and the method of sample collection.
Quantification, identification and antimicrobial susceptibility of bacteria causing urinary tract infection.
Urine culture will be set up per the laboratory standard operational procedure (SOP). Only uropathogens are further tested to identify the bacteria and to perform antibiotic susceptibility testing. Antimicrobial susceptibility is reported according to the cascade policy, designed to report appropriate treatment options.
- No significant growth
The presence of a single type of bacteria growth at high colony counts is considered a positive urine culture. However, it may represent either pathogens or contaminants. The results of a urine culture should be interpreted in conjunction with other pertinent testing information, clinical signs and/or symptoms, and the method of sample collection. Positive urine culture may represent asymptomatic bacteriuria, which should not be treated (except for during pregnancy or before surgical procedures of the bladder). The inappropriate treatment of asymptomatic bacteriuria is a significant antibiotic stewardship problem.
Urine culture should NOT be requested for inappropriate reasons including:
- Asymptomatic screening, or patient request.
- Abnormal urine dipstick or urine microscopy.
- Change in appearance of urine (color, odor).
- Routine pre- or post-operative screening.
- Test of cure after treatment.
- Previous urinary tract infection.
- Fever or delirium without genitourinary symptoms. Although urine culture is routinely performed for these reasons, asymptomatic bacteriuria cannot be ruled out, so positive results may be detrimental to patient care.
Garcia Lynne S., ed. Clinical Microbiology Procedures Handbook. 3rd ed. Washington, ASM Press, 2010
Test Frequency and Turnaround Time (TAT)
Urine culture is a routine test performed daily, Monday to Sunday.
Turnaround time is up to 48 hours from receipt by the laboratory.
Routine bacterial culture.