Question

An 88 year old woman resides at Happy Daze nursing home. She shows signs of mild dementia, sits in a chair most of the day due to arthritis and ambulates aided by a walker. She takes meds for hypertension, hyperlipidemia and edema and has used no form of estrogen in at least 30 years. She has confirmed urinary tract infections 4-6 times yearly. One morning, her caregiver is unable to coax patient out of her bed. She seems confused and disoriented. Vital signs reveal tachycardia in the 130’s, respirations 22/min and hypotension 80/50. She is taken to an ER for evaluation. A chest xray and CT of the abdomen are normal. A catheter urine specimen demonstrates signs of UTI (many epithelial cells , tntc wbc, 20-25 rbc, slight protein and much bacteria). She has an elevated WBC count. Sepsis secondary to urinary tract infection is suspected. Your lab has just received this specimen for culture.

4. Are there any other special routine procedures for urine cultures in the clinical setting? If so, explain what else is done and why.

Answer 1

Answer:

Urine for culture and sensitivity is the most common specimen received in microbiology laboratory. It could be easily said that of 100 different samples received in the lab almost 40 - 50 will be urine cultures. Hence, each laboratory has developed certain procedures connected with the sample.

I would try my best to give you what is done before, during and after receiving this sample and reasoning behind these methods and procedures.

• First and foremost, the patient has to be instructed by a competent medical aide how to collect a proper mid-stream urine sample. These could be the nurse In charge or attending nurse or one of the lab technicians who receive patients in the OPD for sample collections. There is a provision on the lab request for this responsible person to put their signature. If any sample give a mixed culture growth, we can tract why sample collection was not proper.
• Once collected in the proper manner, the sample is received in lab and accession done in registers and computer systems immediately noting down the sample collection and sample receiving times. Sample is labelled with the registration number and laboratory number for further ease of processing. It is of utmost importance to process sample as soon as possible or hold it under proper conditions so as not to result in high colony count from the sample just because of delays in processing. Note that urine is very nutritive medium for bacteria to grow.
• Once it is brought to microbiology laboratory, there are 3 things done in a succession: a part of the sample is removed in a tube to centrifuge and look at the sediment once more; a sterile dip slide is dipped in the urine and labelled and immediately put up for incubation. A dip slide is a device with a slide attached to the lid of a sterile container and layered on both sides with culture media like Cled Agar and MacConkey's Agar which are suitable to get all gram negative pathogens on the medium. In dip slide method we try to examine urine in as near normal condition with minimum handling as possible. Thirdly at the culturing laminar flow using sterile wire or plastic loops, urine is spread on 1-2 media which may be MacConkey's Agar and Sheep Blood Agar, so as to ensure that all possible pathogens are covered. Urine sample is spread on agar plated using a colony counting loop which carries a specific volume of urine and it is spread on entire plate so to give isolated countable colonies on the surface of the agar.
• Once culturing done, the sample immediately goes to sample refrigerator where urine is kept until next day morning and cultured plates and dip slide go into proper tray in the incubator to be observed for growth as per the laboratories guide lines after 18 - 24 hours. All tube, dip slide and culture plates are marked with laboratory number and date of processing.
• The centrifuged urinary deposit in tube is sent to microscopy and staining station wherein depending on requesting doctor a simple microscopy to Gram stain or if the clinician suspects an Acid Fast Stain is carried out on the centrifuged deposit.
• A Microbiology work station card is formed with patient details including clinical history and notes made on it what was the processing done and what should be observed and noted down on the same card until and unless the culture is identified by subsequent biochemical reactions and antimicrobial susceptibility test done for ensuring the sensitivity to drugs and Microbiologist in the lab has supervised and seen all process steps and given a final go to release the right report with right identification and susceptibility pattern of the bacterium as well as clinical correlation of the results with medical history and clinical details of the patient.

As mentioned ahead a urine culture is a most common and an important sample received by microbiology lab and utmost care is taken to process it aseptically and properly without creating a need for the patient to collect and send a fresh sample because of negligence in the processing.