New Infectious Disease Test Promises Quick Diagnosis

Early detection of specific pathogens has long been recognized as a vital strategy in the control of infectious diseases because it can lead to timely care of patients and prevent potential outbreaks.

The detection of specific bacteria represents a significant challenge because of the presence of many different species of bacteria in biological samples. Furthermore, for any given species of bacterium, only virulent strains are infectious while other strains of the same species may be harmless or even beneficial to human health.

A team of scientists led by those at McMaster University (Hamilton, ON, Canada) found a way to make DNAzymes, or single-stranded catalytic DNA molecules from a simple test tube technique that allows for isolation of rare DNA sequences with special functions. The team's first success was the development of a molecular probe that precisely recognizes the strain which caused the outbreak of Clostridium difficile infection in Hamilton, Ontario in 2011. This strain was very infectious, resistant to antibiotics and even fatal to some patients. Instead of having to do several different tests to narrow down to a positive identification of the specific strain, the scientists can now quickly pinpoint this superbug using their new molecular probe.

The team obtained an RNA-cleaving fluorogenic DNAzyme (RFD) that can recognize an infectious strain of C. difficile. This DNAzyme not only exhibits no cross-reactivity to other bacterial species, but also is highly strain-selective for C. difficile. The special DNAzyme (catalytic DNA), RFD-CD1, showed exquisite specificity for a pathogenic strain of C. difficile. RFD-CD1 was derived by an in vitro selection approach where a random-sequence DNA library was allowed to react with an unpurified molecular mixture derived from this strain of C. difficile, coupled with a subtractive selection strategy to eliminate cross-reactivities to unintended C. difficile strains and other bacteria species.

Bruno J. Salena, MD, an associate professor of medicine and coauthor of the study, said, “This technology can be extended to the further discovery of other superbug strain-specific pathogens. For example, such technology would prove useful in the identification of hypervirulent or resistant strains, implementation of the most appropriate strain-specific treatments and tracking of outbreaks.” The study was published on December 16, 2015, in the journal Angewandte Chemie International Edition.

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