J Med Microbiol 53 (2004), 455; DOI: 10.1099/jmm.0.05260-0
© 2004 Society for General Microbiology
ISSN 0022-2615
The ‘double-layer tape prep': an improvement to a standard technique
Alice D. Hughes,
Giovanni D. Lorusso and
Donald L. Greer
Departments of Pathology, Dermatology and Medical Mycology, Veterans’ Affairs Medical Center and Louisiana State University Health Sciences Center, New Orleans, LA, USA
Correspondence: Giovanni D. Lorusso (glorus{at}lsuhsc.edu)
The adhesive tape preparation (Scotch tape prep or cellophane tape prep) for microscopic examination of fungal colonies is a standard technique found in manuals of medical mycology (Forbes et al., 2002). The method is fast and inexpensive and allows direct visualization of fungal morphology. The only disadvantage to this technique is that the preparation dries and the tape wrinkles after several hours, making the preparation unreadable. To use the slide for consultation or education at a later time requires making a fresh preparation. Remaking the slide consumes resources and technician time and causes increased personnel exposure to the organism. We propose a very simple, inexpensive additional step that prevents tape wrinkling and drying, thus extending the useful life of the tape preparation to several weeks. We call this variation the ‘double-layer tape prep'.
The standard cellophane tape preparation is performed under a biological safety cabinet following guidelines for laboratory safety. In the standard tape preparation, a 1.5 inch (40 mm) piece of clear cellophane tape is looped back on itself, sticky side out, using forceps. The loop is gently pressed to the surface of the mycelium (Fig. 1a), then gently lifted and unfolded onto a 25 x 75 mm glass slide, to which three or four drops of lactophenol cotton blue stain has been added (Fig. 1b). The sticky piece of tape with fungal structures will adhere to the slide. The layer of lactophenol cotton blue is the biological stain. The morphology of the fungus is observed without the use of a glass cover slip, as the transparent cellophane tape serves this purpose.
View larger version (101K):
[in this window]
[in a new window]
|
Fig. 1. (a) A loop of cellophane tape, sticky side out, is pressed against mycelium. (b) The tape is placed, sticky side down, onto a slide containing three or four drops of lactophenol cotton blue. (c) Lactophenol cotton blue (three or four drops) is added directly on top of the cellophane tape layer. (d) A cover slip is added. No adhesive or mounting medium is needed.
|
|
Our simple variation is this: prepare a standard tape preparation as described above. Then add a second layer of three or four drops of lactophenol cotton blue directly on top of the cellophane tape layer of the standard tape preparation (Fig. 1c). Next, cover with a 24 x 40 mm cover slip (Fig. 1d). The cover slip is held in place by the suction created by the second liquid layer and no other adhesive is needed. The cover slip prevents the tape from wrinkling and the preparation from drying. The fungal morphology remains recognizable for several weeks as opposed to several hours.
The second layer of lactophenol cotton blue serves as an ‘adhesive’ for the cover slip. Presumably, any sterile, clear liquid could be used in the second layer, but we use lactophenol cotton blue as our liquid of choice to hold the cover slip for several reasons: it is readily available in the biological safety cabinet during the procedure; it contains glycerol, which helps to prevent drying (Larone, 2002); and phenol is a component of lactophenol cotton blue and serves as an additional killing agent.
We have tried sealing the edges of the cover slip with fingernail polish to extend the life of the slides further. We concluded that this additional step was not necessary for our needs; the unsealed double layer preparations are typically useable for up to 2 weeks.
 |
REFERENCES
|
|---|
Forbes, B. A., Sahm, D. F. & Weissfeld, A. S. (2002). Bailey & Scott's Diagnostic Microbiology, 11th edn, p. 789. St Louis, MO: Mosby.
Larone, D. H. (2002). Medically Important Fungi: a Guide to Identification, 4th edn, p. 321. Washington, DC: American Society for Microbiology.
TOP
REFERENCES 
