11th Week of SIP

Name: Hardina Hamzah

Topic: Microbiology

Title: Processing of Urine Specimens

Urine culture is commonly done to determine whether the patient has urinary tract infection. A urinary tract infection is a bacterial infection that affects any part of the urinary tract. When bacteria get into the bladder or kidney and multiply in the urine, they cause a UTI. Enterobactericeae species such as, E.coli, Kleibsiella pneunomiae, Proteus mirabilis and Pseudomonas aeruginosa, cause most of the urinary tract infection.

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There are two types of media used and there are TSA with sheep blood agar and MacConkey agar. TSA (Trypticase Soy Agar) with sheep blood agar is useful for the cultivation of a wide variety of fastidious microorganisms. TSA is a general purpose media produced via enzymatic digestion of soybean meal and casein and TSA is frequently the base media of other agar plate type. In this case, it is the base media for blood agar plate. MacConkey agar is a culture medium to grow Gram-negative bacteria and stain them for lactose fermentation. It contain bile salts (to inhibit Gram-positve bacteria), crsytal violet dye (also inhibit Gram-negative bacteria), neutral red dye (to stain microbes fermenting lactose), lactose and peptone.

TSA with Sheep Blood Agar

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MacConkey Agar

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The urine specimen need to be processed immediately as if prolong, the results may not be accurate. The urine is mixed well before inoculating it onto agar plate. 1ml calibrated disposable loop is used and the loop will be immersed into the urine specimen bottle. The sample will be inoculated onto Blood agar plate first and then MacConkey agar plate by making a straight vertical line down the centre of plate and will be followed by series of close perpendicular streaks through the original line. The plates will then be incubated at 35°C aerobically overnight. At the same time, microscopy cell count of the fresh urine specimen has to be done. The urine sample will be transferred to the notch on the slide chamber of KOVA GLASSTIC SLIDE 10 with grids. The urine sample will be transferred by using the capillary tube and the urine sample will be drawn into the chamber resulting in a homogenous suspension of sediment. The cells to be counted are epithelial cells, white blood cells and red blood cells. When there are a lot of white blood cells (eg. >100 cells) that are counted; this can indicate that the patient may be having urinary tract infection.

KOVA GlASSTIC SLIDE

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After office hours or during weekends/public holidays or even there is a delay in transporting urine specimen, the dipslide will be used. The dipslide has three types of media which are Cysteine Lactose Electrolyte Deficient (CLED) agar, MacConkey agar and E.coli agar. CLED agar is a valuable non-inhibitory growth medium used in the isolation and differentiation of urinary organisms. Being electrolyte deficient, it prevents the swarming of Proteus species. Lactose fermenters produce yellow colonies on CLED agar; non-lactose fermenters appear blue. It has a pH of approximately 7.3. The staff nurse will dip the dipslide into the container containing patient’s urine and then seal the dipslide into the bottle. The staff in the laboratory will help to incubate overnight. One disadvantage of using this method is that there will be no urine microscopy cell count.

Uricult Trio Dip Slide

Retrieved from: http://www.oriondiagnostica.com/files/odextra/Clinical%20Microbiology%20brochure/782-03GB_Uricult.pdf

The cultures and dipslides which are made on the previous day will be read on the next day. Usually when there is a mixed growth of bateria (different types of organisms growing), it is considered insignificant and will be recorded as negative. However, when there is predominant growth of only one type of bacteria, it is considered as significant and will be recorded as positive. Enterobacteriaceae species can be identified easily by seeing the morphology of the colonies and to confirm the species, indole test can be done. For example, when E.coli is suspected to grow, indole test is done on the spot to confirm. A small filter paper is used and a drop of indole is placed on the filter paper. Then, the filter paper is rubbed against one of the colonies. When the filter paper turns blue, it indicates positive and it is proven that it is an E.coli. Then the culture will be sent for further test which is sensitivity testing. However, when there is a doubt on the identity of the organism, the organism will sent for identification and sensitivity test.