Abstract
Negative staining technique of Heine is an easy, inexpensive, and rapid way of screening for coccidian parasites of the intestinal tract. But its use as a routine technique for screening of Cryptosporidium, Cyclospora, and Cystoisospora is restricted due to its sensitivity being lower than the gold standard method of modified Ziehl-Neelsen staining. This paper emphasises the modification of original Heine staining technique which has been attempted in order to increase the sensitivity and detection of oocysts of Cryptosporidium, Cyclospora, and Cystoisospora. Modified Heine staining technique using malachite green is a practical, safe, and sensitive method of detecting oocysts in stool specimens. While the modified Ziehl-Neelsen staining technique is still considered the gold standard for the detection of Cryptosporidium spp., modified negative staining technique of Heine using malachite green stain should be considered as the screening technique of first choice.
Highlights
Cryptosporidium spp. and Cystoisospora belli are intracellular, extracytoplasmic coccidian parasites of the intestinal tract and have been recognized as a pathogen in humans since 20th century [1]. It is a well-acknowledged fact that Cryptosporidium and Cystoisospora, which were earlier assumed to be the causal agents of acute diarrhoea merely in animals, have emerged as one of the leading causes of prolonged life threatening diarrhoea in immunocompromised patients in patients with AIDS
Since we found the sensitivity of Heine technique lower than that of gold standard method of modified Ziehl-Neelsen staining, we attempted a modification in the original Heine staining procedure, in order to increase the detection rate of oocysts
Amongst hundred stool sample smears stained with modified acid-fast technique, eight were found to be positive for oocysts of Cryptosporidium, six were positive for oocysts of Cystoisospora belli, and two were positive for oocysts of Cyclospora spp
Summary
Cryptosporidium spp. and Cystoisospora belli are intracellular, extracytoplasmic coccidian parasites of the intestinal tract and have been recognized as a pathogen in humans since 20th century [1]. It is a well-acknowledged fact that Cryptosporidium and Cystoisospora, which were earlier assumed to be the causal agents of acute diarrhoea merely in animals, have emerged as one of the leading causes of prolonged life threatening diarrhoea in immunocompromised patients in patients with AIDS. Microscopic examination of stool specimens using various techniques (e.g., acidfast staining and direct fluorescent antibody (DFA)) is the most frequently employed practice. Concentration of oocysts by sedimentation or flotation may improve detection by microscopic examination [3]
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