Pathogen screening method developed by researchers
Scientists from the Ben-Gurion University of the Negev (BGU) and the Massachusetts Institute of Technology (MIT) said it could give results in 24 hours for air, soil, water, and agricultural produce.
Matrices were enriched with a general pre-enrichment broth in a dilution series and enumerated by most probable number (MPN) estimation using quantitative PCR (qPCR) for rapid screening of amplicon presence.
Environmental samples, including aerosols, soil of various types (sand, sand/clay mix, and clay), wastewater, and vegetable surface (modeled by tomato), were spiked with Salmonella enterica and/or Pseudomonas aeruginosa to determine recovery rates and limits of detection.
These were chosen as they are leading causes of illness, have high survival potential in the environment and are considered difficult to detect accurately at low concentration.
Limit of detection was on vegetable surface 5 colony-forming units (CFU) per tomato and in treated wastewater, 5 CFU L−1.
Researchers said the method identified S. enterica in non-spiked environmental soil samples within a day, while traditional methods took four to five days and required sorting through biochemically and morphologically similar species.
Reliable detection is crucial
Ezra Orlofsky, who led the research while working at the BGU Zuckerberg Institute for Water Research, said rapid and reliable pathogen detection in field samples is critical for public health, security and environmental monitoring.
“Current methods used in food, water or clinical applications rely on labor and time-intensive culturing techniques while activities such as dairy farming, wastewater and runoff treatment necessitates real-time monitoring of pathogens in environment samples.
“This is the first study to comprehensively assess pathogen concentrations in such a broad variety of environmental sample types while achieving multiple pathogen detection with complete parallel testing by standard (or traditional) methods.
"We considerably shortened previous protocols, do not use any name-brand expensive re-agents for DNA extraction and purification, and increased the procedure and workflow to segue easily from raw sample to qPCR assays.”
Researchers recommend applying the method in the future to pathogens such as Staphylococcus aureus (Staph infection) and Campylobacter jejuni.
The work was supported by the US-Israel Binational Agricultural Research and Development Fund (BARD), the Israel Water Authority, BGU's Kreitman School for Graduate Studies, and the Maccabi Fund.
Source: Water, Air & Soil Pollution journal (Springer)
“Rapid MPN-Qpcr Screening for Pathogens in Air, Soil, Water, and Agricultural Produce”
Online ahead of print, DOI: 10.1007/s11270-015-2560-x
Authors: Ezra Orlofsky, Maya Benami, Amit Gross, Michelle Dutt, Osnat Gillor