Faculty members from the Kansas State University College of Veterinary Medicine have developed a faster, more efficient method of detecting Shiga toxin-producing Escherichia coli (STEC) in ground beef, which often causes recalls of ground beef and vegetables.

"The traditional gold standard STEC detection, which requires bacterial isolation and characterization, is not amenable to high-throughput settings and often requires a week to obtain a definitive result," said Jianfa Bai, section head of molecular research and development in the Kansas State Veterinary Diagnostic Laboratory.

The new method developed by Bai and colleagues requires only a day to obtain confirmatory results using a Kansas State University-patented method with the partition-based multichannel digital polymerase chain reaction (PCR) system.

"We believe the new digital polymerase chain reaction detection method developed in this study will be widely used in food safety and inspection services for the rapid detection and confirmation of STEC and other foodborne pathogens," Kansas State Veterinary Diagnostic Laboratory director Jamie Henningson said.

When ingested through foods such as ground beef and vegetables, STEC can cause illness with symptoms such as abdominal pain and diarrhea. Some illnesses caused by STEC may lead to kidney failure and can be life threatening.

"Some E. coli strains do not produce Shiga toxins and, thus, do not affect human health as much," research assistant professor Xuming Liu said. "Because cattle feces and ground beef can contain harmless or less-pathogenic E. coli along with STEC, the most commonly used polymerase chain reaction cannot identify pathogenic E. coli strains in a complex sample matrix."

The new digital PCR test was developed for research and food safety inspections that require shorter turnaround and high throughput, without sacrificing detection accuracy, the announcement said.

"While the current, commonly used testing method is considered to be the gold standard, it is tedious and requires many days to obtain results that adequately differentiate the bacteria," said Gary Anderson, director of the International Animal Health & Food Safety Institute at the Kansas State campus in Olathe, Kan.

The study, "Single Cell-based Digital PCR Detection & Association of Shiga Toxin-producing E. Coli Serogroups & Major Virulence Genes," which describes the test design and results, was published in the Journal of Clinical Microbiology.

Funding for this study was provided by the Kansas State Veterinary Diagnostic Laboratory, with no extramural funding used. The digital PCR technology for co-detection and association of multiple genes is covered by U.S. patent No. 10,233,505, assigned to the Kansas State University Research Foundation, with the principal investigators Bai, Liu and Anderson.