Cryptosporidium infection: diagnostic techniques

Abstract

The aim of this study was to compare a rapid immunological test and a PCR method with the conventional morphological technique for the identification of Cryptosporidium in faecal samples. Cryptosporidium was found in five samples by Kinyoun acid-fast stain. Five samples yielded positive results on immunoassay, three of which yielded negative results on microscopy. Thus, only two patients were positive for Cryptosporidium according to both methods. PCR analysis confirmed only one sample as positive. Non-homogeneous distribution of parasites in stool samples, lack of oocysts in the tested sample and antigenic diversity among Cryptosporidium species may explain the poor agreement among the three tests. Based on our experience, microscopy test with Kinyoun stain is the best and cheapest way to detect Cryptosporidium spp. in faecal samples. With this method, we have found a 5.4% prevalence of Cryptosporidium infection in our area, similar to those reported for other regions of Italy and Europe.

Giardia and Cryptosporidium and public health: the epidemiological scenario from the Italian perspective

“…A low percentage of cryptosporidiosis (0.84%) was also found in subjects living in a mental institution (Giacometti et al 1997). The high prevalence (5.4%) recently registered in immunocompetent diarrheic patients in the Tuscany Region (Central Italy) needs to be confirmed because of the conflicting results obtained from microscopy and molecular data (Magi et al 2006).…”

Protocol for DNA extraction of Cryptosporidium spp. oocysts in fecal samples

“…We believe that the low number of Cryptosporidium oocysts detected on microscopy influences the result, probably due to the heterogeneous distribution in the sample or even by preserving aliquots without the target DNA. Discrepant results between microscopy and PCR were reported by MAGI et al 21 who detected in their samples 20% positivity by PCR, due to the presence of few oocysts distributed in a non-homogeneous form in the analyzed fecal material, similarly to PENG et al 24 with 35.3% positivity suggesting long storage time in formalin of the seventeen fecal samples studied. The general data obtained by PCR (37.23%) in this study resulted extremely positive when compared with those derived from former partnerships performed with protocols sedimented for PCR, in addition to the use of commercial kits for DNA extraction and which resulted in 49.2% and 20.9% amplification of samples 15 .…”

“…, at -20 °C 21,28 or at -80 °C 24 or else, after a drying process with silica 21 . There are reports on the inhibitory effects of potassium dichromate and formalin on PCR that may lead to a false-negative result of this reaction 18,19,25 .…”

Cryptosporidiosis causing severe persistent diarrhea in a patient with multiple myeloma: A Case report and brief review of literature

“…The diagnosis is established by demonstration of oocysts in the stool by the modified acid-fast Kinyoun stain. [3]…”