COMPARISON OF A MODIFIED WET MOUNT TECHNIQUE WITH THE NEGATIVE STAINING TECHNIQUE OF HEINE FOR THE IDENTIFICATION OF CRYPTOSPORIDIUM SPECIES OOCYSTS IN STOOL SPECIMENS
Rania Ayman Tawfik
Department of Parasitology, Faculty of Medicine, Ain Shams University
Background: The symptoms of cryptosporidiosis are not pathognomonic and laboratory veriﬁcation is required to conﬁrm the diagnosis. Most laboratories in Egypt use wet mount as the basic primary technique for stool examination which is not suitable to visualize Cryptosporidium oocysts. There is clearly a need for a simple, rapid yet efficient diagnostic technique for identifying Cryptosporidium species oocysts in stool samples in resource-limited laboratories. Materials and Methods: Stool smears from both fresh and preserved stool specimens were prepared for: staining with Modified Ziehl-Neelsen stain, the modified wet mount technique and the negative staining technique of Heine and its modification. Three mounting media were used in the modified wet mount technique: DPX, clear nail polish and Glycerol jelly. Both methylene blue stain and Lugol’s iodine were used. Results: The modified wet mount technique was more reliable than the negative staining technique of Heine for the identification of Cryptosporidium oocysts. Cryptosporidium species oocysts’ morphology was clear especially with methylene blue stain and the three mounting media used gave similar results. Conclusion: The modified wet mount technique is a rapid, simple and cheap method for identification of Cryptosporidium species oocysts in stool specimens. This technique has many advantages: it enables the examiner to use x100 oil-immersion objective for examination of faecal wet mounts, it can replace permanent staining techniques when a permanent record is not required and it does not dry for several days so that a second opinion can be sought if necessary. It is a suitable technique for resource-limited laboratories as well as a rapid screening method in field studies.