DAVIS, Calif. — When it comes to detecting E. coli and other pathogens on vegetables, there’s no tried-and-true method, and researchers are working to develop faster and more effective systems to remove tainted products before they leave the packing shed.

Three researchers discussed studies on enhanced detection systems June 23 at the Produce Research Symposium sponsored by the Center for Produce Safety at the University of California-Davis.

Gitta Coaker, assistant professor of plant pathology at UC-Davis, said it appears that E. coli O157:H7 is more prevalent in California’s Central Coast region than in the southern desert region, most likely the result of climatic differences.

Session discusses enhanced pathogen testing

She set out to identify non-pathogenic microorganisms found on lettuce leaves that might serve as indicators of E. coli in the plant as well as others that are indictors of conditions that are not favorable for foodborne pathogens.

Finding the effects of rain and humidity may be useful, and the studies may help scientists use species with negative effects on one another to protect against E. coli, she said.

Panelist Drew McDonald, vice president of national quality systems at Taylor Fresh Foods in Salinas, said such profiling is an important part of learning more about how E. coli works.

Trevor Suslow, University of California extension specialist, described the FTA card, which permits storage or “banking” of DNA samples for an extended period, allowing many samples to be taken when a food safety event is happening and examined more fully later.

The cards, made of a filter paper that absorbs and stabilizes the DNA, also may be useful when collecting samples abroad, where facilities are not readily available to analyze samples.

Beilei Ge, assistant professor of food science at Louisiana State University, talked about a new method of testing for salmonella in a variety of produce items.

The LAMP — loop-mediated isothermal amplification — method offers advantages over the more commonly used PCR — polymerase chain reaction methods, she said.

When the reagent PMA — a DNA binding chemical — was introduced, the process was able to differentiate between dead and living cells. The test should be able to improve the ability to control contamination of fruits and vegetables.