Urine Culture & Sensitivity (C/S)

Urine Culture and Sensitivity (C/S) is a microbiology test. Because contamination can change the result, correct collection and transport are important. If antibiotics have already been started, tell the healthcare professional or laboratory because this can affect culture results.

A urine culture looks for bacteria or yeast that can grow from a urine specimen. When significant growth is detected, the laboratory identifies the organism and may perform antibiotic susceptibility testing to help guide treatment.

The quality of the specimen is critical. Contamination from skin or genital flora can produce mixed growth that is difficult to interpret. A clean-catch midstream sample is commonly requested, and antibiotics taken before collection can reduce bacterial growth. Culture findings are interpreted with symptoms, urinalysis and clinical history.

Before culture, a clean-catch midstream specimen is commonly preferred for adults who can provide one. The container should be sterile and the sample transported according to laboratory instructions. If antibiotics have already been started, that should be mentioned because bacterial growth may be suppressed. When the report includes sensitivity testing, ‘sensitive’ or ‘susceptible’ does not mean a medicine should be chosen without considering allergies, pregnancy, kidney function, infection site and local clinical guidance.

Urine culture may be requested when a urinary tract infection is suspected, particularly when identifying the organism and its antibiotic susceptibility would affect treatment. Correct collection technique is important to reduce contamination.

A urine culture is interpreted by combining the organism grown, the amount of growth, symptoms and specimen type. 'No growth' or 'no significant growth' generally means a clinically significant organism was not recovered under the test conditions. When a likely pathogen grows, the report may include antibiotic-susceptibility results to help the treating clinician choose therapy.

Mixed growth can suggest contamination, especially from an improperly collected midstream sample, although interpretation depends on the clinical setting. Antibiotics taken before collection can reduce bacterial growth and produce a negative culture despite ongoing symptoms.

Culture is not a perfect rule-in or rule-out test for urinary infection. Contamination, low bacterial counts, prior antibiotics and organisms that do not grow well under routine conditions can affect the result. A positive culture without urinary symptoms may represent asymptomatic bacteriuria and is managed differently in different patient groups, so treatment decisions require clinical context.

Use a sterile container and follow clean-catch midstream instructions unless another specimen type was ordered. If possible, collect before starting antibiotics when clinically appropriate and instructed. Deliver promptly; refrigeration or preservative requirements depend on the laboratory.