Researchers develop simple and efficient test for diagnosis of diarrheal disease
Novel nucleic acid test could dramatically improve care for underserved populations affected by diarrheal illness.
A team of scientists from Rice University (TX, USA) and the University of Texas Medical Branch at Galveston (TX, USA) have recently developed a simple, highly sensitive and efficient nucleic acid test to rapidly diagnose the diarrheal disease, cryptosporidiosis, which is responsible for 20% of childhood diarrheal deaths in developing countries.
Diarrheal disease currently causes more global morbidity and mortality than HIV, malaria or tuberculosis and, given that effective treatment requires knowledge of the causative organism, an effective diagnostic test is urgently required. Designed in the laboratory of Rebecca Richards-Kortum, Professor of Bioengineering at Rice University, results are read from a paper strip, which indicates whether samples taken from the stool of a patient contain the genetic DNA from the parasite that causes cryptosporidiosis. Commenting on the research, Richards-Kortum explained, “Parasites such as cryptosporidium are more common causes of prolonged diarrhea. Current laboratory tests are not sensitive, time-consuming and require days before results are available. A rapid, affordable, accurate point-of-care test could greatly enhance care for the underserved populations who are most affected by parasites that cause diarrheal illness.”
The currently available diagnostic tests for the disease use techniques such as PCR that amplify pathogen DNA; however, they also depend on specialized equipment that is not available in developing countries. Conversely, the test described in this study relies upon a recombinase polymerase amplification technique that gives similar results to PCR but operates between room and body temperatures. Samples were prepared using a chemical kit that releases all the DNA and RNA in the stool sample, before the purified nucleic acids are combined with recombinase polymerase amplification primers and enzymes, which amplify the pathogen of interest.
“If the pathogen DNA is present, these primers will amplify it billions of times to a level we can easily detect,” said Zachary Crannell, lead author of the study. “The sample is then flowed over the detection strip, which provides a positive or negative result.” Crannell went on to explain that because the enzymes that amplify the pathogen DNA work most efficiently at body temperature, little equipment is needed for the test.
The research group is now working toward producing a low-cost diagnostic that may also be able to test for the presence of other disease-causing parasites. In addition, they are looking to package the components for the test for effective application in a low-resource setting.
Sources: Quick test finds signs of diarrheal disease; Crannell ZA, Castellanos-Gonzalez A, Irani A, Rohrman B, White AC, Richard-Kortum R. A nucleic acid test to diagnose cryptosporidiosis: lab assessment in animal and patient specimens. Anal. Chem. DOI:10.1021/ac403750z (2014) (Epub ahead of print).
