Independent third party performs analytical validation of Menon Biosensors’ assay for detection of toxigenic Clostridium difficile in stool
Menon Biosensors demonstrates superior sensitivity and specificity of its Clostridium difficile assay in 3rd party analytical validation study with the University of Southern California.
San Diego, May 11, 2015 – Scientists at the University of Southern California (USC) recently completed an analytical validation study to evaluate the sensitivity and specificity of Menon Biosensors’ Clostridium difficile. Clostridium difficile–negative patient stools were spiked in triplicate with varied doses of three different clinical isolates of toxigenic Clostridium difficile: NAP1, CDC-200100215, and ATCC9689. The doses tested included 0, 10^5, and 10^6 CFU/mL.
DNA was isolated from stool using the Menon Universal Sample Prep method, a multi-step process that releases DNA from any specimen type with only 3 reagents. Extracted DNA was amplified by a combination of DNA and NMR signal amplification methods with the Menon M2 bioassay. The M2 assay utilizes customized oligonucleotide probes conjugated with magnetic nanoparticles. Presence of Clostridium difficile DNA was detected by quantitatively measuring the NMR spin-spin relaxation time T2, reflecting the distribution of nanoparticles. When no target is present, uniform distribution of nanoparticles occurs resulting in lower T2. When target DNA is present, structures of DNA and nanoparticles are formed resulting in higher T2. The cut-off value for positive results was a T2 difference of 100 milliseconds (ms). An internal control (B. subtilis, another spore-forming bacterium) was included for each specimen and positive and negative controls were included for each batch of specimens.
A total of 72 patient specimens were tested for Clostridium difficile and B. subtilis (internal control). All 72 internal controls tested positive, indicating successful extraction. For PCR-positive specimens, T2 signal measurements ranged from 100.5 to 1241 ms. For PCR-negative specimens, T2 signal measurements ranged from -3.5 to 76 ms. Concordance was observed for 98.6% of specimens (Table).
Molecular Mirroring Technology
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Cross-reactivity tests were conducted to determine the analytical specificity of the assay using other Clostridium species isolated by USC as well as 2 non-toxigenic Clostridium difficile strains. Included strains were C. sordelii, C. perfringens, and 2 non-toxigenic Clostridium difficile strains (BAA1801 and ATCC700057). The Menon Biosensors assay did not cross-react with any of the strains tested, demonstrating high specificity for detection of toxigenic Clostridium difficile in clinical specimens.
Results were presented at the ECCMID conference held in Copenhagen, Denmark, in April 2015. Future tests are planned to validate the assay in toxigenic Clostridium difficile–positive clinical specimens.
The approach has numerous applications in healthcare, food safety, bio-surveillance and many others where pathogen detection is required.
About Menon Biosensors, Inc.
Menon Biosensors is a molecular biochemistry company that provides DNA analysis for the diagnosis of biological pathogens. Menon Biosensors’ microfluidics and M2 NMR platform technology provides superior sensitivity and specificity and minimizes sample preparation, providing best in class sample-to-answer pathogen detection. The technology has been validated by respected third parties in more than 3,000 samples over six years.
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