“Roka’s target capture technology is the only fully integrated nucleic acid based sample preparation technology in the industry,” Dr. Chaney says. “This technology is the initial step in all of Roka’s automated assays and serves to not only add specificity, but to also clean up the sample prior to detection.”
You Might Also Like
Explore This IssueApril/May 2017
Also By This Author
The diversity of sample matrices in food related analyses results in very unique diagnostic application challenges, Dr. Chaney points out. “Our target capture technology helps to address these challenges by providing an ideal sample for downstream amplification and detection by molecular chemistries called transcription-mediated amplification (TMA) and hybridization protection assay (HPA),” he relates.
An RNA based amplification system, Roka’s TMA has been used in clinical diagnostics for many years and was first commercially introduced to the food industry in 2012.
“TMA is still novel within the food industry and many food safety professionals are not aware of the differences between it and incumbent testing methods, like PCR,” Dr. Chaney says.
TMA uses two enzymes to drive the reaction, RNA polymerase and reverse transcriptase, he explains. According to Dr. Chaney, TMA is very rapid, resulting in a billion-fold amplification of the target RNA within 15 to 30 minutes.
“One component of this efficiency is the greater abundance of RNA target in cells as compared to DNA,” he says. “TMA is different from older DNA based chemistries such as PCR in that it is isothermal and autocatalytic. The higher RNA copy number per cell, combined with TMA, results in a very robust amplification that may occur in a shorter timeframe as compared to PCR, which can translate into quicker turnaround times for results.”
All rapid methods have various analytical limits of detection in the enriched sample, Dr. Chaney points out.
“For example, most PCR methods require 104 or more cells per ml, whereas, TMA only requires 102 to 103,” he says. “This becomes quite important to prevent false negatives when considering industry’s move to larger sample sizes and reduced incubation times across an increasingly diverse and complex range of matrices.”
Post TMA, all Roka assays detect any amplified product utilizing HPA, which Dr. Chaney describes as a highly specific chemiluminescent reaction from which the intensity is measured by the Atlas instrument.
“In addition to the detection of any pathogen, each individual sample processed by Roka’s technology includes an internal amplification control, which ensures all reactions occurred,” he says, adding that all of these technologies are automated on the Atlas instrument.
“Our chemistries and controls, coupled with integrated sample preparation on a fully automated platform, translate into faster result times, laboratory efficiency, full traceability, and more accurate foodborne pathogen screening results, particularly for challenging sample matrices,” Dr. Chaney elaborates. “Roka’s technology is routinely utilized in many industry segments, including commercial laboratories, poultry, ready-to-eat meats, produce, dairy, confectionary, ingredients, cereals, multi-component foods, snack foods, and as a tool in pre-harvest food safety.”
TMA is routinely used by Marshfield Food Safety, LLC (MFS), Marshfield, Wis., a firm that specializes in providing customized, onsite process control laboratory services for U.S. food processing operations.
Holding accreditation to ISO 17025:2005 standards with the American Association for Laboratory Accreditation at all nine of its U.S. food testing laboratories, the MFS portfolio includes an extensive list of microbiology and chemistry laboratory test offerings.
“We have been using TMA for qualitative, semi-quantitative, and limits testing for Salmonella for four years,” says Roy Radcliff, PhD, chief executive officer, MFS. “We started using TMA for identifying Listeria species in early 2016, and we have been using it for L. monocytogenes since August 2016.”
Dr. Radcliff says that the ease of use and decreased hands on time are benefits of TMA enjoyed in MFS labs.