Urine Culture, Comprehensive » Pathology Laboratories » College of Medicine

Additional Information:

UFHPL Epic order code: LAB2107149

A single culture is about 80 percent accurate in females; two containing the same organism with a count of 10⁵ or more represent a 95 percent chance of true bacteriuria; three such specimens mean virtual certainty of true bacteriuria. Urinary tract infection is significantly higher in women who use diaphragm-spermicide contraception, perhaps secondary to increased vaginal pH and a higher frequency of vaginal colonization with E coli.¹

A single clean voided specimen from an adult male may be considered diagnostic with proper preparation and care in specimen collection. If the patient is receiving antimicrobial therapy at the time the specimen is collected, any level of bacteriuria may be significant. When more than two organisms are recovered, the likelihood of contamination is high; thus, the significance of definitive identification of the organisms and susceptibility testing in this situation is severely limited. A repeat culture with proper specimen collection including patient preparation is often indicated. Periodic evaluation of diabetics and pregnant women for asymptomatic bacteriuria is recommended.²

Institutionalized patients, especially elderly individuals, are prone to urinary tract infections, which can be severe.³ Cultures of specimens from Foley catheters yielding multiple organisms with high colony counts usually represents colonization of the catheter and not true significant bacteriuria. Most laboratories limit the number of organisms that will be identified when recovered from urine to two. Similarly, most do not routinely perform susceptibility tests on isolates from presumably contaminated specimens. Failure to recover aerobic organisms from patients with pyuria or positive Gram stains of urinary sediment may indicate the presence of mycobacteria or anaerobes.

As the number of patients who are chronically catheterized increases, so does the controversy on what constitutes a diagnostic specimen. Few clinical studies have been performed to support the identification of more then two organisms or implicate usual site flora (e.g., diphtheroids, α- or γ-streptococci, and coagulase-negative staphylococci other than S saprophyticus).

Footnotes

Stamm WE, Hooton TM, Johnson JR, et al. Urinary tract infections: From pathogenesis to treatment. J Infect Dis. 1989 Mar; 159(3):400-406 (review). PubMed 2644378
Andriole VT. Urinary tract infections in the 90s: Pathogenesis and management. Infection. 1992; 20(Suppl 4):S251-S256. PubMed 1294512
Nicolle LE. Urinary tract infection in the elderly: How to treat and when? Infection. 1992; 20(Suppl 4):S261-S265. PubMed 1294514

References

Clarridge JE, Pezzlo MT, Vosti KL. Laboratory Diagnosis of Urinary Tract Infections. In: Weissfeld AS, ed. Cumitech 2. Washington, DC: ASM Press; March 1987.
Ronald AR, Nicolle LE, Harding GKM. Standards of therapy for urinary tract infections in adults. Infection. 1992; 20(Suppl 3):S164-S170. PubMed 1490743
Stamm WE. Criteria for the diagnosis of urinary tract infection and for the assessment of therapeutic effectiveness. Infection. 1992; 20(Suppl 3):S151-S159. PubMed 1490740

CPT Code(s):

87086

Collection Procedure:

First morning specimens yield highest bacterial counts from overnight incubation in the bladder and are the best specimens. Colony count interpretation standards are based on controlled studies from first early morning collections. Forced fluids or random specimens dilute the urine and may cause reduced colony counts. Hair from the patent’s perineum will contaminate the specimen. The stream from a male may be contaminated by bacteria from beneath the prepuce. Bacteria from vaginal secretions, vulva or distal urethra may contaminate transport. Organisms from hands or clothing might contaminate specimens.

Clean-Catch Specimen: It may be easier for patients to urinate into a small clean disposable cup (styrofoam or Dixie). Afterward, collection site staff can transfer the urine to the urine culture container using the special collection straw-puncture device designed for use with the Vacutainer^® tubes. The numbers of bacteria in a clean unused cup are so few as to be inconsequential when the urine transport stabilizer is added. Thoroughly instruct patients on the proper collection of a clean-catch specimen. Patients must be instructed to thoroughly cleanse skin and collect a midstream specimen. Patients should also be instructed to follow the directions provided with the urine collection kit as follows.
Catheterized Specimen: Refers to an in-and-out catheter that is placed into the bladder soley for collection of the specimen and then withdrawn. Do not collect urine from the drainage bag when an indwelling catheter is in place because growth of bacteria can occur in the bag itself. Instead, clean the catheter with an alcohol sponge. Then, puncture it with a sterile needle, and collect the urine in a sterile syringe. Catheter tips are contaminated by the urethra as they are withdrawn; do not culture them.

Collection Instructions

For Males: Wash hands thoroughly with soap and water. Rinse them well and dry them with a paper towel.

Tear open the towelette packages, so the towels can be easily removed with one hand as they are needed. Do not touch any of the inside surfaces of the collection cup.
Pull back the foreskin to expose the head of the penis completely.
Wash the head of the penis thoroughly using first one towelette then the other. Discard the used towelettes into the toilet bowl.
Pass a small amount of urine into the toilet bowl, then pass a sample into the container. Do not allow the container to touch the legs or the penis. Keep fingers away from the rim and inner surface of the container. Fill the container half full.
The urine specimen should be transferred to the Vacutainer^® tube within 10 minutes of collection.

For Females:Wash hands thoroughly with soap and water. Rinse them well and dry them with a paper towel.

Tear open the towelette packages, so the towels can be easily removed with one hand as they are needed. Do not touch any of the inside surfaces of the collection cup.
Remove undergarments and sit on the toilet seat with legs spread widely apart.
With one hand, spread the labia apart to expose the vulva. Keep this hand in place during the washing and urinating procedure.
Use one towelette to wash the vulva well, passing the towelette only from front to back, not back and forth. Repeat this procedure using the second towelette. Discard the used towelettes into the toilet bowl.
Begin urinating into the toilet bowl then, without stopping the stream, insert the collection cup to collect the specimen. Do not allow the container to touch the legs, vulva or clothing. Keep fingers away from the rim and inner surface of the container. Fill the container about half full.
The urine specimen should be transferred to the Vacutainer^® tube within 10 minutes of collection.

Specimen Requirements:

Type: Urine

Container/Tube: Vacutainer^® gray-top urine culture transport tube with preservative

Sample Volume: Add urine to the fill line on a Vacutainer^® gray-top urine culture transport tube.

Storage: Store specimens at room temperature.

Stability (collection to time of analysis/testing):

Ambient: Unstable
Refrigerated: Unstable
Frozen: 14 days

Rejection Criteria:

Unrefrigerated unpreserved specimens more than two hours old may be subject to overgrowth and may not yield valid results.
Unlabeled specimen or name discrepancy between specimen and request label
Specimen in expired transport container
Specimen received after prolonged delay (usually more than 36 hours for urine)
Specimen collected via a Foley catheter

Use:

This test is used to isolate and identify bacteria:

Present in low numbers in the urinary tract.
From females presenting with urethral syndrome, for whom a routine urine culture was not diagnostic.

Methodology:

Culture