Catheter Specimen Urine (CSU)

A clinical diagnosis of catheter associated urinary tract infection (CAUTI) can be confirmed by culture of a urine specimen obtained from a patient with an indwelling catheter with symptoms consistent with infection.
Microscopy is performed on a fully automated cytometry analyser. Manual microscopy is only performed as an alternative if the specimen is not suitable for the automated method. The cytometry or microscopy is used as a screening test to screen out all negative urine samples in the majority of samples. Samples from specific groups will have automatic culture (such as children, transplant, renal, oncology, haematology and obstetric patients).
Urine samples with positive cytometry or microscopy will be cultured for isolation, identification and susceptibility of likely pathogens.
Not all susceptibility test results are routinely released and additional advice can be obtained from the consultant microbiologist if required.
Clinical details: 
The following clinical details will trigger a compulsory culture: recurrent UTI/cystitis, treated UTI, non-resolving UTI, pyelonephritis, reflux. The following wards and patients will trigger a compulsory culture: renal, oncology, obstetrics, paediatrics (<14 years old), urology, haematology.
Synonyms or keywords: 
CSU, in/out catheter sample
cytometry results: RBCs <10/µl reported as non-significant numbers detected, 10-99/µl reported as small numbers (10-100/µl) detected, 100-199/µl reported as moderate numbers (101-200/µl) detected, >199/µl reported as large numbers (>200/µl) detected. WBCs <10/µl reported as non-significant numbers detected, 10-49/µl reported as small numbers (10-50/µl) detected, 50-199/µl reported as moderate numbers (51-200/µl) detected, >199/µl reported as large numbers (>200/µl) detected. Bacterial <400/µl reported as non-significant numbers detected, ≥400/µl reported as significant numbers detected Epithelial cells ≥15/µl reported as Epithial cells detected Samples with a cytometry count of <20/µl WBC and/or <150/µl bacteria are not cultured Manual microscopy - performed if sample unsuitable for processing via automated cytometry or in event of instrument failure, all samples are cultured if manual microscopy is performed.
Sample type and Volume required: 
Catheter urine. Please send 10ml in a green topped monovette urine tube containing boric acid.
The sample may be obtained from a transient ‘in and out’ catheterisation or from and indwelling catheter (urethral or supra-pubic). Samples from indwelling catheters should be obtained aseptically from the sample port in the catheter tubing and not from the collection bag.
Samples recieved in the department by 19.00 will be cultured the same day, microscopy is performed 24/7.
Turnaround time: 
Microscopy/cytometry 4hrs, negative culture 1 day, postive cultures 2-3 days.
Storage and transport: 
Collect urine into a green topped monovette boric acid tube, fill to the line (10ml) please send in Universal Container if <10ml of urine available. Place labelled sample in a sealed sample bag and send to Central Specimen Reception (CSR). Samples should be refrigerated if transport to the laboratory is delayed.
Infection Sciences Department at St Thomas' Hospital
020 7188 8008
St Thomas' Hospital
North Wing - 5th Floor
Westminster Bridge Road
London SE1 7EH
Core opening hours: Monday-Friday 0900-1730

For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 27/11/2017