Scientists pitch in to help keep salad mixes safe to eat

June 14, 2011

It's no wonder that packaged salad mixes are a produce section favorite. They offer convenience, selection, and quality, and perhaps best of all, they free us from the chore of washing and chopping, slicing, or shredding salad greens.

But outbreaks of foodborne illness have, from time to time, been associated with bagged salad greens. The outbreaks have led the fresh-cut produce industry to voluntarily adopt stringent quality-control standards.

U.S. (USDA) food safety researchers are pitching in to help keep salad mixes safe to eat. Innovative studies led by Agricultural Research Service (ARS) Maria T. Brandl are providing new information about the impressive array of genes that a major foodborne pathogen, Escherichia coli O157:H7, calls into action when attempting to colonize leaves of fresh-cut lettuce.

ARS is USDA's principal intramural scientific research agency. This research supports the USDA priority of ensuring food safety

Mechanical cutting of lettuce leaves into large pieces or shredding of leaves into narrow strips, like those in taco filling, breaks lettuce cells, explains Brandl. The broken cells exude carbohydrates, which the microbe can use as a source of energy. But injured cells can also leak such as that are problematic for the pathogen.

A study with romaine lettuce that Brandl and her coinvestigators published in in 2010 showed that E. coli, when exposed in lab tests to the contents of broken lettuce leaf cells, can adapt quickly. Using an approach known as microarray-based whole genome transcriptional profiling, the researchers determined that the pathogen uses its genetic arsenal to protect itself against not only the , but also against oxidative stress, osmotic stress, damage to its DNA and other threats to its ability to survive and multiply.

The investigation--the first to provide extensive details about the biology of E. coli O157:H7 in fresh-cut lettuce--has paved the way for followup experiments that Brandl and coworkers hope will lead to new technologies to overcome the pathogen's defenses.

Explore further: Lettuce object of California health study

Related Stories

New romaine lettuce lines launched

January 18, 2011

California and Arizona, the two largest lettuce-producing states, account for more than 95% of the lettuce grown in the United States. Since the early 1990s, the states' lettuce crops have been subject to "dieback", a disease ...

E. coli an unlikely contaminant of plant vascular systems

April 1, 2011

A technique developed by U.S. Department of Agriculture (USDA) scientists for tracking pathogens has helped confirm that Escherichia coli is not likely to contaminate the internal vascular structure of field-grown leafy greens ...

Recommended for you

Research advances on transplant ward pathogen

August 28, 2015

The fungus Cryptococcus causes meningitis, a brain disease that kills about 1 million people each year—mainly those with impaired immune systems due to AIDS, cancer treatment or an organ transplant. It's difficult to treat ...

Genomes uncover life's early history

August 24, 2015

A University of Manchester scientist is part of a team which has carried out one of the biggest ever analyses of genomes on life of all forms.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.