Cryptosporidiosis (crypto) is a nasty GI disease caused by a protozoan parasite present in unclean drinking water. Being able to quickly detect the infection would help treat patients presenting with complementary symptoms. To that end a team from Rice University and the University of Texas Medical Branch have developed a test strip, that looks similar to a pregnancy test, for detecting crypto without expensive laboratory equipment.
After a bit of preparation, a (typically diarrheal) stool sample is introduced to the test strip, which in turn detects the presence of the parasite’s DNA using recombinase polymerase amplification (RPA). This allows for field testing for crypto at room temperature and without having to use equipment typically required for PCR.
In Rice’s experiments, samples were prepared with a commercial chemical kit that releases all the DNA and RNA in the small amount of stool tested. The purified nucleic acids are then combined with RPA primers and enzymes tuned to amplify the pathogen of interest, Crannell said.
“If the pathogen DNA is present, these primers will amplify it billions of times to a level that we can easily detect,” he said. The sample is then flowed over the detection strip, which provides a positive or negative result.
The RPA enzymes are stable in their dried form and can be safely stored at the point of care without refrigeration for up to a year, he said.
While current tests might catch the disease in samples with thousands of the pathogens, the Rice technique detects the presence of very few – even one – parasite in a sample. In their experiments, the researchers reported the presence or absence of the disease was correctly identified in 27 of 28 infected and control-group mice and all 21 humans whose stool was tested.
Rice: Quick test finds signs of diarrheal disease…
Study in Analytical Chemistry: A Nucleic Acid Test to Diagnose Cryptosporidiosis: Lab Assessment in Animal and Patient Specimens…