Urine sample should be collected and sent for culture only when there is strong evidence/suspicion of infections of the urinary tract to avoid detection of asymptomatic bacteriuria.
Common symptoms of UTI are:
Frequency of urination
Burning sensation during urination
Dysuria (painful urination)
Pain above the pubic region
Cloudy, bloody or strong-smelling urine
Flank pain or pain above pubic area
Urine collected by noninvasive methods passes through the contaminated milieu, so quantitative cultures is used for the diagnosis of Urinary Tract Infections (UTI) and to discriminate between contamination, colonization (asymptomatic bacteriuria) and infection.
Positive cultures could mean
Commonly used methods for urine specimen collection:
Suprapubic aspiration: Suprapubic aspiration is the best method to avoid contamination of specimens with bacteria in the distal urethra. Urine is withdrawn directly into a syringe through a percutaneously inserted needle. This type of collection technique may be indicated in pediatric practice.
Straight catheter technique: Collection of urine by use of a single catheter (straight catheter technique) is the next-best technique for obtaining urine specimens with minimal contamination
Clean Catch Midstream Urine Collection: It is the least invasive technique and used widely. It has obvious disadvantage compared to techniques mentioned above. The chances of contamination from normal vaginal, perineal and anterior urethral flora is high. Urine sample passes through the distal urethra and can become contaminated with commensal bacteria.
Indwelling Catheter: Specimen collection from patients with indwelling catheter requires scrupulous aseptic technique. The catheter tubing should be clamped off above the port to allow collection of freshly voided urine. The catheter port or wall of the tubing should then be cleaned vigorously with 70% ethanol, and urine aspirated via a needle or syringe; the integrity of the closed drainage system must be maintained to prevent the introduction of organisms in to the bladder.
Related Post: Microbial Etiology of Urinary Tract Infections (UTI)
Urine specimen collection techniques and frequency of their use:
- Clean-catch midstream technique: Most urine specimens are obtained from adult patients via the clean-catch midstream technique
- Suprapubic aspiration: Used infrequently because it is not indicated clinically (except in rare circumstances), it is invasive and uncomfortable, and it requires too much time and too many resources to be practical.
- Straight catheter technique: It is not indicated clinically for most patients because it is too labor intensive and costly for routine use. It is an invasive techniques with added disadvantages, because the process of inserting a catheter through the urethra can introduce bacteria into the bladder (and thereby cause UTI), and rare complications have been reported.