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DIP SLIDE FOR CLINICAL USE

CODE: DS0102

The Oxoid Dip Slide is made of easily disposable plastic. Its raised edges ensure an even thickness of culture medium. It has a moulded grid, which makes colony counting easier, and is shaped to ensure drainage of fluid from the slide. The surface area of the agar layer on each side is 700 sq.mm.
Dip slides are simple and safe for an unskilled operator to use. The sterile Dip Slide can be inoculated on the ward or doctor’s surgery. It is then returned to its plastic container for transportation to the laboratory.

Introduction
Kass (1956) defined significant urinary tract infection by a quantitative assessment of the bacterial population of freshly voided urine and was able to differentiate between infection and contamination. This led to many cultural and chemical methods being devised, to quantify the bacterial population in urine.
All these methods depend upon freshly voided urine being delivered promptly to the bacteriological laboratory for examination, either immediately or after a short period of refrigerated storage. Mackey and Sandys (1965, 1966) devised the method of filling a spoon with solid medium and using this as a dip-inoculum transport medium, thus avoiding misleading impressions produced by proliferation of organisms in urine between collection and arrival at the laboratory.
The “Dip Slide” was developed as a logical extension of this method (Guttman and Naylor 1967, and Guttman and Naylor 1967). Using a microscope slide coated on each side with a different culture medium, larger areas of media could be used for bacterial assessment of urine. The glass slide was easy to contaminate, and there were also the risks of cuts if the glass was broken.

Method of Use
The aim is to wet both sides of the Oxoid Dip Slide with a mid-stream specimen of urine. This can be achieved in either of 2 ways:
1. by collecting a mid-stream specimen in a sterile container and then dipping the Dip Slide in the urine.
2. an alternative “dip-stream” procedure was developed by Arniel (1972). The patient begins to urinate and after the stream is well established, the Dip Slide is held into it sufficiently to thoroughly wet each side.
The Dip Slide is held vertically for a moment to allow surplus urine to drain off the tip and then returned to its sterile plastic container. Care must be taken not to touch the agar surface. The patient should be carefully instructed in the technique to follow.
The patients name and details of date and time etc are noted on the label of the container and the Dip Slide is either posted or taken to a laboratory for subsequent incubation and examination. Samples sent through the post may already be positive on receipt in the laboratory. Apparently negative samples should be incubated at 37ºC for at least 18 hours before being discarded.

Oxoid Dip Slides are available for the following purposes:

Evaluation of results

Comparison of growth on Dip Slide

Interpretation of Dip Slide Results
Kass (1956) stated that contaminant bacteria in fresh urine are fewer than 104 organisms per ml, whereas infecting organisms exceed 105 per ml. Tests made with known bacterial suspensions of 104 per ml produce around 20 colonies on the Dip Slide. Suspensions containing 105 organisms per ml will produce around 200 colonies. The Dip Slide, therefore, provides its maximum discrimination over the range of viable bacterial counts which is most helpful in the diagnosis of urinary tract infections (Naylor and Guttmann 1967).

Disposal of used Dip Slides
Used Dip Slides can be incinerated, autoclaved or soaked overnight in a suitable disinfectant, such as hypochlorite or a phenolic or quaternary ammonium compound product.

Storage of Dip Slides
Dip slides can be stored at 10–25ºC. Refrigeration at 4ºC is acceptable but may result in the release of water condensation. Do not use dip slides beyond the stated expiry date, or if the products show signs of deterioration.