In search of food-borne pathogens via filtration
06/01/2004
BY STEVE SMITH
CLIFTON, N.J.—A collaborative work between separations technology vendor Whatman, Inc. (www.whatman.com) and the Food and Drug Administration (FDA; www.fda.gov) seeks to devise a faster and more accurate method of detecting food-borne pathogens by using size-exclusion filtration in combination with Whatman's proprietary FTA filter technology.
The FDA has used a comparatively time-consuming, standard bacteriological method for sample preparation and analysis to determine whether food and the wash used for leafy vegetables are infected with harmful pathogens. The agency decided to partner with Whatman to improve and speed that process, including the ability to detect pathogens on-site.
Whatman's proprietary FTA technology is a chemical treatment that allows for rapid isolation of pure DNA. When samples are applied to FTA-treated filters, cell lysis—loosening or destruction—occurs, and high-molecular weight DNA is immobilized within the food matrix. Among its cited benefits, the technology is designed to kill pathogens and prevent future colonization by bacteria or fungi, allows archiving of samples at room temperature, and reduces potential for cross-contamination between samples.
In the two-year project, Whatman will supply the FDA with reagents and filters to perform the necessary work, and will participate in a validation study using a combination of size-exclusion and the company's own FTA filters. It is hoped that the determined best method could then be applicable to any type of food matrix and have practical application to environmental and water samples.
"Not only will this science benefit the [FDA] project, but ultimately, we hope for it to be adopted as the standard application for the rapid analysis of food and environmental safety," says Dr. Martin Smith, Whatman's vice president of research and development.
The two participants are hopeful that, at the conclusion of the study, the determined method will serve as a universal polymerase chain reaction (PCR) template preparation protocol for the rapid detection in all foods of such pathogens as bacteria, parasitic protozoa and viral particles.
Study: Product-related contamination depends on how you handle it
Veggies may be part of the four food groups, but a recent agriculture industry study indicates that when it comes to foodborne illnesss outbreaks, produce is mainly guilty by association.
Strict government regulations and adoption of "good agricultural practices" are key factors in why only two percent of all traceable foodborne illness outbreaks in the U.S. come directly from the growers, according to analysis commissioned by the Alliance for Food and Farming (Watsonville, Calif.; www.foodandfarming.info).
"Contrary to some recent reports, 88 percent of foodborne illness outbreaks were traced to foods other than fresh produce," says Marilyn Dolan, executive director of the Alliance. The analysis, encompassing data from the Centers for Disease Control from 1990 to 2001, indicates that most foodborne illness outbreaks associated with produce can be avoided by improved handling at the food service level, as well as with improved consumer education on food preparation.
According to its analysis, of all foodborne illnesses traced to produce over the 11-year period, 83 percent were associated with improper handling at the food service or consumer levels. And since produce growers adopted "good agricultural practices" in 1997—developed jointly with the federal government to provide guidelines that reinforce stringent laws governing food safety on farms—data indicates that foodborne-related illness attributed to the farm have dropped by 131 percent.
The simple solution for much of the produce-related foodborne illness, says the Alliance, is to wash hands before handling fresh fruits and vegetables, wash the produce before serving, and don't use utensils, counters, plates or cutting boards that have been in contact with raw meat, poultry, seafood, or eggs.
As evidence that consumer education is lacking, the Alliance says that in a recently conducted survey, 51 percent of consumer attribute the main cause of produce-related outbreaks to the farm rather than due to improper handling. At the same time, however, the Alliance acknowledges that the increasing introduction of international produce into the U.S. marketplace can make their education campaign difficult.
While the study claims that "good agricultural practices" have successfully provided food safety guidelines that reinforce existing stringent laws governing food production, "due to the increasing globalization of the food supply, many recent large-scale produce-related outbreaks have been the first of their kind." The study cites widespread outbreaks of Cyclosporta cayetanensis in 1995 and 1996 associated with Gautemalan raspberries. The five outbreaks comprised 21 percent of the confirmed etiology outbreaks and 39 percent of produce-related foodborne illnesses over those two years.
Not satisfied with the results, the Alliance says the agricultural industry must continue to reduce any on-farm incidents of foodborne outbreaks, and work to "implement processes, which have been successful in reducing risk on the farm, such as good agricultural practices." —SS