Urine Culture test

Urine Culture test


An etiological diagnosis of bacterial urinary tract infection by quantitative cultivation of the urine with identification and susceptibility test of the isolated bacteria

Types of specimen: Urine (Midstream urine), suprapubic aspiration, catheterized urine.

Criteria of specimen rejection

Urine Culture test

Un-refrigerated specimen older than 2 hours may be subject to overgrowth and may not yield valid results; unlabeled specimen; mislabeled specimen; specimen in expired transport container; 24 hours urine specimens.

Common pathogens

Neisseria gonorrhoeae                     E. coli and other Enterobacteriaceae Enterococcus spp                               Staphylococcus aureus

Staph saprophyticus                            Corynebacterium jeikeium

Acinetobacter spp                               Pseudomonas spp

Gardnerella vaginalis                       β-haemolytic streptococci

Salmonella spp (early stage of infection)

Commensal flora

Diphtheroid bacilli                    Lactobacillus sp

Coagulase negative Staphylococci                 α Haemolytic Streptococci

Bacillus spp                                       Non-pathogenic Neisseria spp.

Anaerobic cocci                                Commensal Mycobacterium

Commensal Mycoplasma spp.


Schistosoma haemetobium                                    Trichomonas vaginalis

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 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. Receptacle must be sterile.

Time relapse before processing the sample

The maximum time allowed for processing a urine sample is 2 hours from the time of collection

Storage: At room temperature unless delay is inevitable; it must be refrigerated

Specimen processing

Media1. Blood Agar,2. MacConkey Agar3. Nutrient Agar

Culturing procedure

Mix the urine sample to re-suspend microorganism present. Dip a 1 μl calibrated loop in vertical position in the urine and remove the loop and use the collected fluid to inoculate a nutrient agar plate that will be used for urine plate count.Take another loop to streak Blood agar and another loop to streak MacConkey agar plates. Streak the Nutrient agar plate to cover all surface area.A plate count of 10,000 CFU/ml of pure culture should be considered positive and isolated organism should be identified and sensitivity test will be performed.

Post specimen processing

Interfering factors: Patient on antibiotic therapy. Improper sample collection.

Result reporting: Report wet mount as an initial report. Report the isolated pathogen and its sensitivity pattern as a final report.

Turn around time:

Wet mount results should be available 1 hour after specimen receipt. Isolation of a possible pathogen can be expected after 2-3 days. Negative culture will be reported out 1-2 days after the receipt of the specimen.

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