Urine Culture, Comprehensive

Semiquantitative culture to isolate and identify bacterial causes of urinary tract infection. Isolate and identify bacteria present in low numbers in the urinary tract. Detect up to three pathogenic bacterial organisms at levels down to 100 cfu/mL.

Unrefrigerated unpreserved urine specimens greater than two hours old may be subject to overgrowth with organisms normally present in the urethra and periurethral areas, and may yield inaccurate or misleading results. If specimens are incorrectly submitted with an order for aerobic bacterial culture, the laboratory will process the specimen for the test based on the source listed on the request form. The client will not be contacted to approve this change, but the change will be indicated on the report.

Culture

A single culture is about 80% accurate in the female; two containing the same organism with count of 100,000 cfu/mL or more represent a 95% chance of true bacteriuria; three such specimens mean virtual certainty of true bacteriuria. 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. Cultures of specimens from Foley catheters yielding multiple organisms with high colony counts usually represents colonization of the catheter and not true significant bacteriuria. Failure to recover aerobic organisms from patients with pyuria or positive Gram stains of urinary sediment may indicate the presence of mycobacteria or anaerobes. Few clinical studies have been performed to support the identification of more than two organisms or implicate usual site flora (eg, diphtheroids, α- or γ-streptococci, and coagulase-negative staphylococci other than S saprophyticus).