Diagnosis of urinary tract infection (UTI).
Urinary tract infection (UTI) results from the presence and multiplication of bacteria in one or more structures of the urinary tract with associated tissue invasion. This can give rise to a wide variety of clinical syndromes. Infection may spread to surrounding tissues (e.g., perinephric abscess) or the bloodstream (bacteraemia, septicaemia). In contrast the presence of certain types of micro-organisms in urines other than catheter urines (e.g., S aureus including MRSA, Candida) may be a sign of bacteraemia or candidaemia rather than UTI.
An important part of the investigation of UTI is bacteriological culture.
Microscopy of the specimen is undertaken to quantify the number of white blood cells, red blood cells and to detect whether there are bacteria or yeast present.
Culture and antibiotic sensitivity testing is also carried out, to determine what, if any, bacteria are present and the antibiotic sensitivity pattern. Clinical details provided tailor the tests carried out on the sample.
If the patient can collect urine without assistance from nursing staff, they should be instructed as follows:
- Separate the labia with cotton wool or sponge moistened with water (disinfectant MUST not be used).
- Wipe the vulva from front to back.
- With the labia still separated, allow some urine to pass into the toilet.
- Without stopping, allow urine to pass into a sterile, red-topped borate container (as seen in container section) and fill to the line.
- Pass remaining urine into the toilet
- Clean the penis with soap and water.
- Commence urination and allow a few millilitres to pass into the toilet.
- Without stopping, allow urine to pass into sterile, red-topped borate container (as seen in container section) and fill to line.
- Pass remaining urine into toilet.
In elderly or very ill patient, nursing assistance may be required. Ensure that there is minimal chance for contamination of the sample. Specimens showing signs of contamination, for example, with faecal matter, are of no value and will not be cultured.
- Disinfect the catheter specimen port using an alcohol wipe.
- Clamp tubing below the sampling cuff.
- Clean the sampling cuff with an alcohol wipe.
- Aspirate urine using a syringe and transfer to a sterile boric acid container.
- Unclamp the tubing.
Use red-topped universal containers that contain boric acid for bacterial culture and microscopy. Must be filled to the minimum fill line.
Paediatric/small volume urines (less than 10ml) should be sent in 7ml red-topped sterile universals with boric acid.
Minimum fill line is displayed on the universal label.
- Adults: 20ml
- Paediatrics: 5ml
Limitations and restrictions
- Contaminating bacteria from the external genitalia may give rise to misleading results.
- If unable to obtain 5ml or more of urine, the accuracy results may be affected due to insufficient dilution of the boric acid crystals – collect the urine in a white-topped universal container. This type of sample needs to be at the laboratory within 2 hours of collection.
Microbiology Lab, James Cook University Hospital, Marton Road, TS4 3BW
If delays in delivery to the laboratory are expected samples should be refrigerated at 2-8°C.