Neogen launches test to detect E. coli O157:H7

ANSR (amplified nucleic single temperature reaction) for E. coli O157:H7 is the fourth test for the ANSR pathogen detection system, and will provide results after 10 minutes of reaction time following sample preparation.

With ANSR’s single-step enrichment, Neogen’s pathogen detection method can provide results in 12 hours from time the sample is taken.

The test joins Neogen’s line of ANSR products, which includes AOAC Research Institute-validated tests for Salmonella, Listeria and L. monocytogenes; an approval for the E. coli ​O157:H7 test is pending.

Test kit sensitivity​

Sensitivity of the ANSR test kits is 1 CFU per portion, said Kristen Antonellis, product manager, pathogens.

“For example, this translates to being able to report less than 1 CFU per 325g of raw ground beef. The titer of the ANSR enrichment in order to detect 1 CFU per portion is 10^4 CFU/mL. This is true for the Salmonella, L. monocytogenes and E. coli kits. The level is 10^2 CFU/mL for Listeria species​.

“Easy single-step enrichment protocols coupled with an easy lysis step means ANSR delivers on the promise of being the easiest. With a 10 minute assay, the speed rivals lateral flow devices, but has the specificity of a molecular assay.”​

The test works by placing a portion of the enriched culture into a cluster tube. A lysis reagent is added which disrupts the cell and releases the nucleic acid target molecules.

The lysed sample is transferred to the preheated ANSR reagents in the reader. ANSR reagents consist of a molecular beacon and special primers that target specific regions of the pathogen DNA. Amplified segments of the pathogen DNA attach to special molecular beacons.

These beacons fluoresce when bound to the pathogen DNA and this is detected in real time by the ANSR reader.

The procedure can also use the USDA-recommended media (modified TSB). The test has been validated for testing raw ground beef, raw beef trim, leafy greens and sprout irrigation water.

Antonellis said it is focusing on the matrices validated but if there is a need in the marketplace for additional ones it will revisit validation.

Neogen’s ANSR is an isothermal amplification reaction test method that amplifies the DNA of any bacteria present in samples to detectable levels in minutes.

The ANSR system was designed to combine molecular-level accuracy with a low-cost instrument and a methodology that can be incorporated into a testing laboratory’s existing workflow.

“Some of the work we’ve done developing NeoSeek for STEC confirmation leads us to believe that the genomic diversity of pathogenic E. coli requires significant multiplexing to provide a reliable diagnostic​,” said Antonellis.

“With NeoSeek STEC confirmation we use 86 targets to provide the necessary specificity for the top seven STECs.”​

Lab M ISO accreditation​

Meanwhile, the quality control laboratory of Lab M’s facilities has been granted ISO 17025:2005 accreditation by the United Kingdom Accreditation Service (UKAS). Lab M was acquired by Neogen in August.

Lab M’s schedule of accreditation covers the physical and microbiological performance testing of the company’s Pinnacle media range. 

The five methods accredited include pH, sterility, fill volume, qualitative performance testing and quantitative performance testing. All methods are based on requirements of BS EN ISO 11133:14. 

“The requirements of BS EN ISO 11133:14 have been considered throughout the expansion of our Pinnacle range. This newly published standard has been a major focus of all manufacturers and users of culture media​,” said Lyn Richards, quality assurance and regulatory affairs manager at Lab M.