One of the challenges is that even if molecular-based testing confirms the presence of viral genome, it can’t discriminate whether the virus is active and potentially infectious or inactive and noninfectious.
“There are various technical issues to detect them – it’s been quite difficult to work with viruses,” Sánchez said. “That’s one of the main reasons we didn’t pay that much attention until the last few years.”
To that end, the researchers examined the effectiveness of markers incorporated into qPCR-based testing methods to assess the infectivity of enteric viruses. Once they validated sample collection and testing in a laboratory setting, they used it to assay wash water samples collected monthly in three produce processing facilities.
“The water we are using even in the lab experiments is not being generated in the lab – it’s the water coming from the processing facilities as a result of the strong collaboration with them and the great interest on this topic,” Sánchez said. “Working under real conditions gives us a real picture of the quality of the water used in their facilities. And we can perform the experiments in a manner that is close to reality when transferring our results.”
The researchers also plan to examine whether coliphages – viruses that infect E. coli – can be used as reliable indicators of potential contamination because they can mimic enteric viruses.
“We know that fecal bacteria are not good indicators of viruses,” Sánchez said. “One option is to use phages as a fecal virus indicator because their structure is pretty similar to human enteric viruses. We’ll use these in parallel to see if we can correlate viruses and the phages in wash water.”
In addition, the researchers plan to evaluate the efficacy of common sanitizers used in processing facilities as well as establish operational conditions and critical parameters for each system to inactive enteric virus and coliphages. The three sanitizers to be tested are chlorine, peracetic acid and chlorine dioxide.
Initially, the researchers inoculated water samples from the processing facilities with enteric viruses and phages to gauge inactivation by sanitizer concentrations and contact times.
The next step will be to conduct similar experiments at a pilot plant at CEBAS that uses higher volumes of process wash water and a dynamic system to represent commercial conditions.