Supermarket Perimeter - June 2022 - 56

Food safety
Traceability
BY ANDY NELSON
SCIENTISTS WITH THE USDA'S AGRICULTURAL
RESEARCH SERVICE (ARS) aim to enhance the
capacity of regulatory agencies to trace Escherichia coli
(E. coli) O157:H7 back to its source during a foodborne
outbreak investigation by studying how the DNA of a
specific population of E.coli gradually evolves within its
natural environment.
Food contaminated with E. coli can cause serious
illness, hospitalizations, and even death.
The findings from scientists at the US Meat Animal
Research Center (USMARC) at Clay Center, Neb., equip
outbreak investigators with information on specific
elements of the bacterium's DNA that can narrow where
to look for the outbreak source.
As these bacteria are found naturally in the intestines
of cattle, the team of scientists analyzed samples
collected from the center's closed cattle feedlot from
1997 to 2019 and studied the genomes (the organism's
genetic composition) of various strains, or subtypes, of
E. coli O157:H7 found in samples.
" The samples used in this research gave us a
unique opportunity to study the genomes of a
specific population of E. coli O157:H7 in their natural
environment,˝ said Maggie Weinroth, a computational
biologist with the Poultry Microbiological Safety and
56 - JUNE 2022
supermarketperimeter.com
Researchers are using
cutting-edge DNA
technology to aid in
tracing E. coli outbreaks
back to their source.
Processing Research Unit in Athens, Ga., who was
working at USMARC at the time of the research.
" The USMARC feedlot has been closed to any
introduction of cattle, except those raised in the center.
This means that the E. coli strains have not been
influenced by cattle from other locations for 23 years,
allowing us to focus on changes in the bacteria genomes
as they evolved over those years,˝ said Weinroth.
The scientists identified four unique clades within the
specific bacteria population they studied. (Clades are a
group of organisms that share specific characteristics.)
Even though all clades shared a portion of their genetic
composition, each clade also contained unique elements
that can be shared, called mobile elements.
" Looking only at the core elements of the genetic
sequences may not tell the complete story about
where the bacteria came from,˝ said USMARC Research
Microbiologist Jim Bono. " We noticed that bacteria
were able to exchange mobile elements in their genome
over time. Some of these elements stayed in all strains
and became part of the core sequence of that specific
bacterium's DNA. Interpretation of these mobile
elements' role during an outbreak investigation can help
identify relatedness between human and environmental
isolates of this bacteria. "
AXEL KOCK, GESHAS, PINEAPPLE STUDIO, ETIENNE VOSS, IURII KACHKOVSKYI, MARA ZEMGALIETE - STOCK.ADOBE.COM; ALBERTSON'S

http://www.supermarketperimeter.com

Supermarket Perimeter - June 2022

Table of Contents for the Digital Edition of Supermarket Perimeter - June 2022