A novel photoinduced electron transfer (PET) primer technique for rapid real-time PCR detection of Cryptosporidium spp

Comparison of Three Real-Time PCR Assays Targeting the SSU rRNA Gene, the COWP Gene and the DnaJ-Like Protein Gene for the Diagnosis of Cryptosporidium spp. in Stool Samples

As qualified microscopy of enteric parasitoses as defined by high diagnostic accuracy is difficult to maintain in non-endemic areas due to scarce opportunities for practicing with positive sample materials, molecular diagnostic options provide less investigator-dependent alternatives. Here, we compared three molecular targets for the real-time PCR-based detection of Cryptosporidium spp. From a population of 1000 individuals comprising both Ghanaian HIV (human immunodeficiency virus) patients and military returnees after deployment in the tropics, stool samples were assessed for Cryptosporidium spp. by real-time PCR targeting the small subunit ribosomal RNA (SSU rRNA) gene, the Cryptosporidium oocyst wall (COWP) gene, and the DnaJ-like protein gene (DnaJ), respectively. In declining order, sensitivity of 100% for the SSU rRNA gene PCR, 90.0% for the COWP PCR and 88.8% for the DnaJ PCR, respectively, as well as specificity of 99.6% for the COWP PCR and 96.9% for both the SSU rRNA gene PCR and the DnaJ PCR, respectively, were recorded. Substantial agreement (kappa value 0.663) between the three assays was observed. Further, an accuracy-adjusted Cryptosporidium spp. prevalence of 6.0% was calculated for the study population. In conclusion, none of the assessed real-time PCR assays were associated with perfect test accuracy. However, a combination of highly sensitive SSU rRNA gene PCR for screening purposes and more specific COWP PCR for confirmatory testing should allow reliable diagnosis of Cryptosporidium spp. in stool samples even in low prevalence settings.

A novel single-labeled fluorescent oligonucleotide probe for silver(I) ion detection in water, drugs, and food

Due to the high toxicity of silver(I) ions, a method for the rapid, sensitive, and selective detection for silver(I) ions in water, pharmaceutical products, and food is of great importance. Herein, a novel single-labeled fluorescent oligonucleotide (OND) probe based on cytosine-Ag(I)-cytosine coordination and the inherent fluorescence quenching ability of the G-quadruplex is designed to detect silver(I) ions. The formation of a hairpin structure in the OND-Ag(I) complex brings the hexachloro fluorescein (HEX) labeled at the 5'-end of the OND probe close to the G-quadruplex located at the 3'-end of the OND probe, leading to a fluorescence quenching due to photoinduced electron transfer between HEX and the G-quadruplex. Through this method, silver(I) ions can be detected quantitatively, the linear response range is from 1 to 100 nmol/L with a detection limit of 50 pmol/L, and no obvious interference occurs with other metal ions with a 10-fold concentration. This assay is simple, sensitive, and selective, and it can be used to detect silver(I) ions in actual water, drug, and food samples.